# Battery Box Design



## DIYguy (Sep 18, 2008)

A couple things that come to mind right away as a basic for heating/cooling is keeping all the batteries at a fairly even temperature. They could be in larger boxes, smaller boxes and mixed. For both heat and cooling. 
I'm going to talk about LiFePo prismatics right now since that is my current need (selfish as it is ). 
- I can see aluminum sheet under batts for a couple reasons. It will help to distribute the heat in larger boxes as well as when used with heating elements smaller than the battery area sitting on it. It has good thermal conductive properties and is relatively light. 

- I can also see the opportunity to use the spacing created by the ribbed battery cases to allow air (heat/cool) to move through the pack/stack or whatever.

- assuming prior point has some value, a space is required between Al sheet and batteries that allows air movement. (have a few ideas here TBD). Space may reduce contact with Al sheet... but heat still rises off of the entire sheet... oh yes... forgot to mention, this sheet/space mentioned is on the bottom!

- assuming prior two points have some value.... I would propose that cooling through ventilation (fan) would be best handled by drawing air out of enclosed bat box as opposed to forcing it in. I say this because I am envisioning the need to distribute forced air along a thin space at the bottom as opposed to venting this bottom space along the edges (and closing off in winter) and creating suction or exhausting possibly out the top. This would draw air up through all the passages between the battery cases.

That's enough for now... Thoughts? holes? flawed thinking??


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## rwaudio (May 22, 2008)

I'd like to see where this goes, I haven't designed my boxes yet (for Headways) but I will need some sort of heating. I grabbed a cheap waterbead heater off ebay, it's pretty sturdy, completely sealed slightly flexible I think it would work well when you are plugged into 120, and could probably be setup to run off of pack voltage as well. The one I got is 120V @ 1A, (120w) there are also 350w versions but that might be too much. I've already designed temperature sensors into my charging boards that will be in each battery box, so that might be able to cycle the heater as necessary.


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## DIYguy (Sep 18, 2008)

rwaudio said:


> I'd like to see where this goes, I haven't designed my boxes yet (for Headways) but I will need some sort of heating. I grabbed a cheap waterbead heater off ebay, it's pretty sturdy, completely sealed slightly flexible I think it would work well when you are plugged into 120, and could probably be setup to run off of pack voltage as well. The one I got is 120V @ 1A, (120w) there are also 350w versions but that might be too much. I've already designed temperature sensors into my charging boards that will be in each battery box, so that might be able to cycle the heater as necessary.


Yes, I think water bed heaters are one of the better options. Couple things l like about them...as you mentioned flexible and waterproof and readily available as well as inexpensive. Most come with control also. One thing that may need tweaking is the temp range...as most are in the 70 - 100F range. Perhaps an additional thermal switch would do it. The other thing (for me) is that it would work good for my bigger boxes, but I have a couple of smaller ones that may not be suitable. 
The other thought I had was to pick up one/some designed for Europe market and be able to run from 240VAC or my pack voltage of 210VDC or so.
Here is another interesting option...although, not quite as cheap.
http://www.kimhotstartheaters.com/category/565146

Ahhhh, look what I found...  http://www.standbypowerservicecompany.com/battery_pads_wraps_specs.pdf

Apparently, the Silicone ones are not for use on batteries..... http://www.standbypowerservicecompany.com/silicone_hot_pads_specs.pdf

Here's another one... but it says not to use in an insulated battery box... http://www.padheaters.com/battery_heater.html

Another one... http://www.alpha.ca/web2/products/battery-accessories/battery-heater-pad.html

http://www.warehouseautoparts.com/Specialty_Line/Kat/kats_battery_pad_Blanket_heaters.htm

and another... http://alpha.ca/Documents/Brochure/Battery%20Heater%20Mats_10_A002.pdf . . and this one.... http://www.alpha.ca/web2/products/battery-accessories/battery-heater-mats.html


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## DIYguy (Sep 18, 2008)

Maybe some radiant floor heating stuff will work also... ??

http://www.archiexpo.com/prod/cbs-radiant-heating-systems/underfloor-heating-mat-9811-24026.html


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## rwaudio (May 22, 2008)

I bet those silicone ones would work nice under an aluminum heat spreader. Otherwise it might be tricky finding a size that really works well for even one persons variety of battery box sizes.


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## TheRedBaron (Jan 31, 2011)

To switch to cooling for a sec., you could created/buy an aluminium heat sink and computer fan combination. I don't know how big your box is going to be but you could easily run a comp. fan off of 12v.


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## Yabert (Feb 7, 2010)

Hi canadian guys!..

Yes the cold wheater will be an issue.

You can see bellow a parts of my future headway battery pack.
I will use 3/8 lexan at the end, at base and for the upper. Both side will be aluminium sheet metal. 

For hot temperature, I will think use two small 12v fans. I plan the holes, but i'm not sure to use it because overheat will maybe not a issue with a small car like a Smart.

Concerning cold winter, I think use Easy heat roof de-icing cable or Pipe Tracing Heating Cables. They are rated at 7w/feet and I think use 18' for 126w and less than 1A at 156v. They cost 30-40$.


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## EVfun (Mar 14, 2010)

Have you considered heating the air you are moving? It could be a recirculating system when heat is needed, with the air drawn out by a fan and heated then directed back in the other side. When cooling is needed open the loop drawing fresh air in and exhausting it (heater off naturally.)


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## Tahoe Tim (Feb 20, 2010)

EVfun,
I was thinking the same thing. If you are going to add ventilation fans, simply heat the same air.


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## Jan (Oct 5, 2009)

I’m still chewing on this: http://www.che.sc.edu/faculty/popov/drbnp/website/Publications_PDFs/Web26.pdf

I hate the authors by now pretty much. With their endless repeating and using sentences that never seem to end. And words they chose to confuse normal people on purpose.

I’ve found a few interesting things so far. But a lot is still not clear to me. Cell formation is one of the interesting things. But is not important in this topic. It’s like formatting a hard disk. 

There is a lot about temperatures. The aging test are done at different temperatures: -10, 0, 25 and 50C. The absolute degradation of the cells is the worst at -10. But relatively it’s worse at 50C. The initial capacity at -10 is from the beginning much lower than at 50C. 

I haven't read yet what the capacity of these cells that where aged at -10 is at 25C after the >5000 cycles. That's very important. But I’m slow.

My gut feeling tells me: high temperatures (but below 60C) is good for short term performance. You have higher capacity and more power available at that particular moment. But at the cost of earlier long term capacity and power losses. 

You have to choose between these two firstly before designing a battery box. Do you want maximum performance right now? Or do you want your cells to last as long as possible? 

Also take in consideration that the cells are heaters by themselves. If the insulation is sufficient you don’t need extra heating. Only the first few miles might be a bit under powered.


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## ElectriCar (Jun 15, 2008)

I'm thinking of having some built using aluminum. This time I want boxes with a top too. I'm thinking of insulating bottom and sides with this stuff. Its' 5/32" thick and about R4 I think. Diamond plate is expensive I heard and after a while will be dingy anyway. I was wondering what else I should use. How about billet sheets? 

Thermostatically controlled muffin fans with louvers in the top of the sides would help remove heat in summer and soil heaters could warm them in the winter.


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## JRP3 (Mar 7, 2008)

Jan said:


> My gut feeling tells me: high temperatures (but below 60C) is good for short term performance. You have higher capacity and more power available at that particular moment. But at the cost of earlier long term capacity and power losses.


I agree that up to a point heat is good, as long as you don't get electrolyte break down and stay below that point I'm not sure what the mechanism is that would cause early losses.


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## JRP3 (Mar 7, 2008)

ElectriCar said:


> I'm thinking of insulating bottom and sides with this stuff.


What about the top where you'll have most of your heat loss?


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## ElectriCar (Jun 15, 2008)

I didn't think about the top as my old box is more of a rack with no top. But yea the top would be good too in winter. In "the video" they say to limit the temp to 55-60C I think. Calb said keep it below 60 which I think you saw that in the post I made with their reply on another thread. 

I'm thinking of modifying the rack and setting these boxes on the modified rack frames.


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## ruckus (Apr 15, 2009)

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## ruckus (Apr 15, 2009)

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## ruckus (Apr 15, 2009)

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## ruckus (Apr 15, 2009)

The manual for the Thundersky LFP260ah batteries shows they only loose about 10-12% range at -25C (-13F) compared to 25C (77F). 

They loose about 20% range at -45C (-49F). But that is COLD.   (even for Canada)

The small reduction in range doesn't seem like much to worry about.  

I am sizing the batts ~25% big so they will still meet the range requirement as they age (or when the temps drop).

LFP seem less affected by cold than lead.


--sorry, that's what happens when U use the back button to edit... :|


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## toddshotrods (Feb 10, 2009)

Naturally, my thoughts are going to be out on the extreme edges, but maybe there's something in them that can benefit someone.  One thing that may help is the fact that I am trying to keep the cost of the cases down to allow for easier adoption of newer technologies. I'm planning on nano-tech LiPo cells, and want heating/cooling because of how hard I want to push the pack.

I'm currently leaning towards liquid climate control. I'm toying with the idea of using rectangular aluminum radiator tubing to build an egg crate-like divider structure that would flow liquid around the individual cell packs. The same system could take care of the controller and battery pack. With a small radiator in a ducted box and a heating element inside, it could cool or heat.


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## Ziggythewiz (May 16, 2010)

@ruckus You know, they do let you add your comment all at once, as opposed to a line at a time


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## rwaudio (May 22, 2008)

ruckus said:


> The manual for the Thundersky LFP260ah batteries shows they only loose about 10-12% range at -25C (-13F) compared to 25C (77F).
> 
> They loose about 20% range at -45C (-49F). But that is COLD.   (even for Canada)
> 
> ...


Either headways are affected very differently or the Thundersky data isn't quite right. (Or they include self heating which means the cell doesn't actually stay at any of the numbers quoted)
At 0degC it looks like headways are at about 95% Capacity
At -10C about 82.5%
At -20C about 60%
I would be willing to bet there isn't much capacity at -45C

This is based on a 0.3C discharge which doesn't produce enough heat to raise the cell above ambient temperature. Most vehicles are going to draw more than that so there will be some self heating.


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## ruckus (Apr 15, 2009)

I checked the manual and it specifies that for the test the cell should be normally charged and then left for 12 hours in -25C before the discharge test of .3C. 

I do not think they are counting on cell heating.

Does anyone have testing or experience to add about how much range is affected using LIFEpo4 in the cold?


-They do specify that during the AK-47 shooting test no flames should appear, but smoke is allowed.


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## JRP3 (Mar 7, 2008)

Also consider that charging the cell when cold the resistance will be higher, so voltage would increase faster before the cell is actually full. So if you stop charging at similar voltage when the pack is cold you'll get less charge into the cells, and because of increased resistance you'll have greater voltage sag on discharge and pull greater amps for the same power output. At the very least you probably want warm cells when charging even if you don't have warm cells when discharging.


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## DIYguy (Sep 18, 2008)

Wow, miss a day .. miss a lot.  Thanks for all the feedback. Some good ideas in there. I hadn't thought much about recirc air heating and dump for cooling. hmmmm. I was thinking radiant for heat and then a quick mod of some kind to allow air in and suck out for cooling. Have to think about this. As for temp impact, I did spend some time looking at this and there are quite a few users of Lifepo who can attest to fairly significant losses in colder temps. There may be some benefit with LiFeYPo...but so far no data... just "seems better" from some folks. I know lead chemistry is best suited to around 75 F. As for lifepo...well, guess that is being discussed as to wants and wishes...peak performance vs pack life/charging/range etc.

My boxes are steel angle iron frame with exterior grade plywood, treated and painted black. I've been wanting to go away from the wood this time around, not that it won't likely outlast the truck...but just seems a bit out of place. I know a lot of folks have used the plastic "sign board" material...and I was thinking along this line but wanted something different. One thing I want is to have it black so it doesn't stand out when looking under the truck. I dont think paint is going to stick to the plastic sign boards very well. I found this "foam board" from "Elmers" (the glue ppl). It's black and has some fine foam inside and covered both sides with a plastic of some kind. It's crazy light and I bought a sheet for experiment. I took a couple of pics... not sure if they will be revealing, but I'll upload. Oh, just Google it...there are lots of pics...
I'm thinking of this for the sides. I may put something else inside for more insulation...or look at thicker board (what I have is 5mm).


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> I'm thinking of having some built using aluminum. This time I want boxes with a top too. I'm thinking of insulating bottom and sides with this stuff. Its' 5/32" thick and about R4 I think. Diamond plate is expensive I heard and after a while will be dingy anyway. I was wondering what else I should use. How about billet sheets?
> 
> Thermostatically controlled muffin fans with louvers in the top of the sides would help remove heat in summer and soil heaters could warm them in the winter.


Hey Electric...
Couple thoughts. As for the bubble wrap... I have it inside my boxes now. On the plus side, I think it does a pretty good job for it's thickness. On the minus side, the bubbles will all deflate on the pieces under the batteries and it will turn into alum foil with plastic flat sandwich..  The other thing...be careful with it around batteries and don't even think of using it on the top...that foil on the outside definitely conducts! Ask me how I know. It can work fine on the sides as long as you don't let it poke up too high.

As for the Aluminum sheet... you know, just a personal thing, but I think this is not the best for use in colder climates. The thermal conductivity of Al just seems so counterproductive to the process of heating a box. I would definitely use it to spread heat under the batts inside the box...but not so sure about the sides. It definitely looks great and it's light. Perhaps if you have a good insulation inside it, it will be fine.

Edit... oh yes, and definitely a top is required if want to control this environment. . . at least when it's cold and ur trying to keep them warm.


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## DIYguy (Sep 18, 2008)

For those who would add some type of electric element to heat... what are your thoughts on powering? 
115VAC, 230VAC (or whatever your supply is?) 
Pack voltage so you can heat when away from a plug?
Dual power so you can do either?


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## DIYguy (Sep 18, 2008)

Here are a few pics of what I did the first time. . . Just for discussion/interest. Oh, and all my boxes are bolted in with SS hardware so they can be removed (thank god I did this!) lol and modified.


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## Overlander23 (Jun 15, 2009)

DIYguy said:


> For those who would add some type of electric element to heat... what are your thoughts on powering?


I'm using Farnham pads under the cells, separated by aluminum sheet to diffuse the heat. They are all powered by 110/120v AC, plug in to the wall when parked. Idea is that draining during driving will keep them up to temp. But I also don't need to keep the vehicle parked remotely all day.


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## DIYguy (Sep 18, 2008)

Overlander23 said:


> I'm using Farnham pads under the cells, separated by aluminum sheet to diffuse the heat. They are all powered by 110/120v AC, plug in to the wall when parked. Idea is that draining during driving will keep them up to temp. But I also don't need to keep the vehicle parked remotely all day.


Thanks Overoander. Do you have any pics? 
Even though I park mine inside a garage that I usually heat.... I often wonder if I shouldn't design this next setup to be fully flexible for any situation. Even if I don't ever need to heat the batteries after sitting for 8 hours in -25C at work somewhere...if I were to ever sell it ..... ya, hmmm. I dunno. 
Seems like every time I justify a decision to do something on the "short"... like, oh, I'll upgrade later...or I can make this better when I change the other thing.... I always end up wishing I had done it "right" (better/different...whatever) the first time.


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## Jan (Oct 5, 2009)

JRP3 said:


> I agree that up to a point heat is good, as long as you don't get electrolyte break down and stay below that point I'm not sure what the mechanism is that would cause early losses.


It's pretty wel documented on the net. The thickness of SEI layer increases slowly, and all other stuff happens during the life of a cell. But I'm not really interested in the chemical processes. Way to complicated for me. I’m only interested what it means to us, EV users. Hard enough to extract this info out of scientific documents.

After reading more and more scientific documents about li-ion cell aging I’ve come to some conclusions and considerations, I want to share. Again.

To be clear: With aging I mean the inevitable capacity and power fade of a li-ion cell, that starts directly after production and will fasten by using them. 

It's not about taking it beyond its extremes, by over charging them or over discharging them. That’s not aging, but murder.

*Calendar aging*

Li-Ion cells age whether you use or store them, linear to temperature. The higher the temperature the faster the aging. They age faster at 50C than at 0C. So, you should store them at the lowest possible temperature. 

I can’t find a minimal lowest temperature. Using a deeply frozen li-ion cell will give of course very limited to zero power. 

Manufacturers sometimes advice 20C in their spec sheet. But I haven’t found any scientific evidence for 20C as the bottom limit. Probably the difference in aging below 20C might be very insignificant.

This process of calendar aging is sometimes confused with leaking. It’s not leaking, the capacity fade can’t be regained by recharging, like in a chemistry that loses capacity due to leaking.

There is little scientific documentation about voltage and aging while stored. All manufacturers advice below or around 50%, while some give a lowest limit of 30%, and one advices the lowest voltage possible (the cut off voltage). My guess is that it doesn’t mean much below 50%.

*Aging under EV circumstances*

Using a Li-Ion cell will obviously fasten the aging process. But there are facts to consider. The aging increases at higher currents. As well during charging as discharging. Higher currents decrease the lifecycles in all circumstances. Not to be confused with the Peukert effect, which is a temporary effect.

During charging extra accelerated aging is documented in the CV phase, and heavily depends on the voltage used in this phase. The higher the voltage, the faster the aging. It’s advised in regards of cell life to avoid the CV phase at much as possible. 

In regards to discharging; going beyond 80% DoD accelerates the aging process also. This depends heavily on the brand, some start their accelerated aging near 70%, while others only start noticeably beyond 90% DoD. 

In conclusion, to get maximum cell life one should keep the cells as cool as possible, but not to cool to lose necessary power. Furthermore stay away from the CV phase, and above 20% SOC (With some brands above 30%). And keep the current in all cases as low as possible. Take for CC charging as long as possible, if you have the time.

Design your pack, if cell life is your main goal, with an over capacity of 140%, to be able to stay between 20 and 80% SOC. And with the highest Ah possible considering space and weight. Which means of course all the same: try to stuff as much cells as possible in your car.

*Maximizing performance*

To get the maximum performance of your pack, you should disobey all these rules. Except of course for the last rule: to stuff as many as possible in your pack. 

To get max power and capacity, you should heat the cells to the highest possible temperature, just before the electrolyte starts to boil. Usually somewhere around the 60C. 

And by using the highest allowed voltage during charging (especially the CV phase), the capacity can be increased.

Of course at the price of accelerated aging. But once in a while that shouldn’t hurt too much. Or if you’re a (drag) racer, than it comes with the sport.

*Cell drift*

If you stay between 20 and 80% SOC of your weakest cell, and you’re able to maintain an equally temperature across your pack, cell drift should be very insignificant.

If not, cell drift might occur, because some cells will age faster than others, because they are more abused in the low and/or high end of SoC, and temperature differences across your pack will age cells differently too.

The aging of cells is, at normal and higher temperatures, mainly visible in the lower SoC area. While voltages stays the same in the larger and higher part of the SoC, it starts to diffuse in the lower areas. At lower temperatures (below 10) it is visible across the whole SoC spectrum.

This means that In a bottom balanced pack the voltage difference between the drifted cells will differ across the whole SoC of the pack. In a top balanced pack in the larger and top area of the SoC the voltage wil be pretty much the same at normal temperatures.

I can’t determine what’s best. And in regards of CMS I’m still not sure. I guess, that it will be very different if you’re high performance vs. long life oriented. Under high performance circumstances cell aging and drift will be much more of an issue. Very much more. I doubt a simple half pack voltage comparison will be useful under these circumstances, with rapid aging and cell voltages all over the place.

But I’m more interested in maximizing cell life. 

*Cell formation*

Another thing is cell formation. The first cycles in a cell’s life are very important. The video professor mentioned it already. He mentions that a lot of the cells future could be determined in this phase of the cell. But he doesn’t state anything specifically.

I’ve found, so far, that (again) reduced temperatures, and reduced current flows (C/25) can increase the capacity of the cell (de-aging), while the opposite, high temperatures and high currents during this life phase will extra fasten cell aging, more than later on in its life. 

If true, assemble your pack at the end of the summer/fall, and start to use it (very moderate) in that following winter. Use the this first winter only for testing and cell formation. If your place on earth has something that could be called a winter of course.


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## JRP3 (Mar 7, 2008)

That's a pretty good summary.


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## ElectriCar (Jun 15, 2008)

DIY I like your battery box in the back. What are the dimensions and what year is your S10? I've got a 91.


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## Jan (Oct 5, 2009)

JRP3 said:


> That's a pretty good summary.


Thanks, JRP3.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> DIY I like your battery box in the back. What are the dimensions and what year is your S10? I've got a 91.


Thanks. It's a 97 Mazda B4000.. .
I think just over 28" x 28" if I recall right....
Truck looks like this.....


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## DIYguy (Sep 18, 2008)

Yes, awesome write-up... thanks Jan.



Jan said:


> During charging extra accelerated aging is documented in the CV phase, and heavily depends on the voltage used in this phase. The higher the voltage, the faster the aging. It’s advised in regards of cell life to avoid the CV phase at much as possible.


Would it be fair to say that it's the upper voltage level (typically seen in the CV phase) that is responsible? . . . as opposed to being the state of constant voltage and tapering current?
I mean, if your algorithm went into CV phase at 3.38Volts compared to CC charging to 3.8 and pulling the plug.... u know what I mean? None the less, a good point right there.



Jan said:


> *Cell drift*
> 
> If you stay between 20 and 80% SOC of your weakest cell, and you’re able to maintain an equally temperature across your pack, cell drift should be very insignificant.
> 
> ...


I'm not totally convinced about this drift thing.... seems there is some evidence of temps playing a role....(and maybe even these bounce back pretty much when evened up in temp)... outside of that issue, there is no mechanism for causing drift according to prof... 

Thanks again. awesome....


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## ElectriCar (Jun 15, 2008)

EVfun said:


> Have you considered heating the air you are moving? It could be a recirculating system when heat is needed, with the air drawn out by a fan and heated then directed back in the other side. When cooling is needed open the loop drawing fresh air in and exhausting it (heater off naturally.)


This could be done with an external blower and dryer hose or small insulated AC flex duct. Some fine expanded metal under the batteries would facilitate good air flow but may need a small space between it and the box bottom to get enough air flow. Have a diverter duct valve of some sort you could open for warm weather. 

Mr. Jack built some boxes out of carbon fiber. Wonder if he did a video on it? I'd have to have a pot of coffee though to get through it. His videos make me sleepy! But a cf box if sturdy enough would be a good weight saver and much better at heat retention than aluminum. And cheaper probably than aluminum. I think it would be easy to build them as well using card board for a form.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> This could be done with an external blower and dryer hose or small insulated AC flex duct. Some fine expanded metal under the batteries would facilitate good air flow but may need a small space between it and the box bottom to get enough air flow. Have a diverter duct valve of some sort you could open for warm weather.
> 
> Mr. Jack built some boxes out of carbon fiber. Wonder if he did a video on it? I'd have to have a pot of coffee though to get through it. His videos make me sleepy! But a cf box if sturdy enough would be a good weight saver and much better at heat retention than aluminum. And cheaper probably than aluminum. I think it would be easy to build them as well using card board for a form.


My .02 on the heating side of it... I think radiant from below is easiest... with the space as you describe it would all waft up. Lid keeps it in. All u need. If you wanted to heat via recirc, you would need to draw from one part (top or bottom) and feed back in the opposite. 
W
To cool with the radian set up...all you need to do is allow air in the bottom space and suck out the top thermo controlled. 

Also, I found some interesting plastic mesh stuff that would work for bottom spacing and allow airflow. I'll post it up when I get a sample.


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## JRP3 (Mar 7, 2008)

ElectriCar said:


> Mr. Jack built some boxes out of carbon fiber. Wonder if he did a video on it? I'd have to have a pot of coffee though to get through it. His videos make me sleepy!


They key is to download the video and then play it in VLC player at faster speed, I find 1.8 times normal to be just about right


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## ElectriCar (Jun 15, 2008)

We seriously need to look at carbon fiber containers. Check out this site. Look at the 13.5lb cantilever structure holding up 500lbs! This stuff is unbelievably strong AND light. Expensive to buy but not to make. Apparently a sheet or two of glass make for a good mold to make uniform flat sheets. 

Here's a DIY article for sheet making. This stuff is neet! Check out this guy and what he's built! It needs further evaluation as I know NOTHING about this stuff until tonight.


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## Duncan (Dec 8, 2008)

Be careful of carbon fiber - it can be very strong BUT
If you make two panels using the techniques in that article 
one S glass, one carbon fiber
the carbon fiber piece will be heavier than the S glass piece and have a lower strength to weight ratio 

This is because the carbon fiber is more difficult to "wet out" so you end up using more resin

If you are using a wet layup (not pre-pregs) S glass is stronger and cheaper!

Also the resin used is important - use Epoxy for strength, if you are going to use polyester then use normal glass matt - S glass is an overkill! and carbon or kevlar are silly


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## toddshotrods (Feb 10, 2009)

Carbon fiber gets it awesome reputation from vacuum-bagged and autoclaved parts (and probably infusion too). Any composite's ultimate strength is heavily dependent on the resin to cloth/mat ratio. More resin results in a weaker, heavier, part. I haven't had any problems with wet-out using carbon fiber cloth. I've been playing with composites for a long time, so maybe I'm just used to it? The biggest issue with wet lay-up is it doesn't like to conform to complicated mold shapes. That's the other big benefit of bagging it. You can also use 3M Super 77 or 90, to stick the cloth to the mold surface, and then wet-out like normal. I like PVA mold release.

I don't see any problem with a carbon fiber/S2 composite. CF/fiberglass composites are actually pretty popular in automotive parts because it yields a stronger part, with a _pretty_ face, and cuts the cost significantly. I checked out some very high quality CF/glass composites hot rod parts last year. They were bagged though.


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## Jan (Oct 5, 2009)

DIYguy said:


> Would it be fair to say that it's the upper voltage level (typically seen in the CV phase) that is responsible? . . . as opposed to being the state of constant voltage and tapering current?
> I mean, if your algorithm went into CV phase at 3.38Volts compared to CC charging to 3.8 and pulling the plug.... u know what I mean? None the less, a good point right there.




Yep, I guess you’re right. It’s about pushing the upper voltage level. Pushing more Ah’s in the cell. 



> I'm not totally convinced about this drift thing.... seems there is some evidence of temps playing a role....(and maybe even these bounce back pretty much when evened up in temp)... outside of that issue, there is no mechanism for causing drift according to prof...




Maybe the Prof assumes top balancing, while I prefer(ed) bottom balancing. I wasn’t clear when I wrote this about the balance option. Let me try again:

The facts as I interpreted them from scientific literature:

Aging is mostly visible in de lower SoC. The low voltage knee will start a little sooner every cycle, and changes shape over time. While the higher and larger part of the SoC spectrum stays the same. At normal (most) temperatures.

Aging is accelerated at both ends of the charge and discharge process. It’s like a pretty flat line, that changes in a hyperbolic curve at both ends. A cell that can do 2000 cycles before going under 80% capacity charged to 80% SoC, drops to 1000 cycles at 90%, and maybe 200 at a 100%. While the difference between 70% and 80% SoC is quite insignificant.

If you push your pack to the limits and/or with large temperature differences across the pack, these little differences will inevitably grow. Weaker cell will go deeper and sooner in the hyperbolic part of the curve than stronger cells. And temperature differences will cause different speeds in aging too. The weak will get weaker faster every time.

If you have a top balanced pack, these differences will not be visible in most part of the SoC (Let say from 30% up). Some cells will hit the deep DoD knee earlier than others every cycle. And since you have a top balanced pack, you have to watch this phenomena carefully anyway. I wouldn’t call this drift.

But in a bottom balanced pack it’s completely different. You will loose the balance because at the bottom cells will drift apart. Some can not reach that ‘collective’ bottom any more, while other cells have no problem. I see that phenomena as drift. Because you have to (re)balance your pack regularly. Not so much in the beginning, but as the whole pack ages more often.

But if you stay away from the edges as much as possible, and keep the temperatures in your pack equal, I guess this drift will not be very significant in a bottom balanced pack soon.

I really dislike this, because I was convinced (by JRP3) that bottom balancing was the way to go. But a top balanced pack with a half pack voltage difference meter could be a good alternative. 

Anyway, the link to this topic is that cooling is important for cell life. And that cold cells, with a limited range is a temporary problem, while hot cells can become a big permanent problem. And that the temperature must be as equal as possible throughout the boxes.


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## JRP3 (Mar 7, 2008)

Jan said:


> Aging is accelerated at both ends of the charge and discharge process. It’s like a pretty flat line, that changes in a hyperbolic curve at both ends. A cell that can do 2000 cycles before going under 80% capacity charged to 80% SoC, drops to 1000 cycles at 90%, and maybe 200 at a 100%. While the difference between 70% and 80% SoC is quite insignificant.


 On the other end, discharge, there is a significant difference between 80%DOD and 70%DOD.




> But in a bottom balanced pack it’s completely different. You will loose the balance because at the bottom cells will drift apart. Some can not reach that ‘collective’ bottom any more, while other cells have no problem. I see that phenomena as drift. Because you have to (re)balance your pack regularly. Not so much in the beginning, but as the whole pack ages more often.


 I guess you are assuming that a top balanced pack is using active balancing to keep it together. Since you can only actively top balance by pushing the SOC higher into the knee each charge, and if you are correct that cycle life significantly decreases going from 80%SOC to near 100%SOC, top balancing might be a bad idea. Frankly I'm pretty convinced with the closely matched packs we can now get it doesn't really matter which way you balance the pack since they'll be almost as balanced at both ends.


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## Jan (Oct 5, 2009)

JRP3 said:


> On the other end, discharge, there is a significant difference between 80%DOD and 70%DOD.


Yep, my example is pure fiction. In reality it depends on the brand. Not just the used materials and chemicals, but more about what the manufacturer defines as 100% SoC. Some advertise with the maximum, while others are much more conservative. An 180Ah CALB has nearly the same amount of energy capacity as 200Ah Thunderskies. 

This will result in where you will exactly start to see the beginning of the hyperbolic part of the aging curve. Well, you will only see it when it's to late of course.

That's why you must use of course the documentation that comes with the cells. But keep in mind that it is not a linear curve, but a linear curve for a large part, with a hyperbolic trend at the high SoC. And this can start somewhere between 60% and 90%.



> I guess you are assuming that a top balanced pack is using active balancing to keep it together. Since you can only actively top balance by pushing the SOC higher into the knee each charge, and if you are correct that cycle life significantly decreases going from 80%SOC to near 100%SOC, top balancing might be a bad idea.


No, I don't mean that a top balanced pack regurlarly needs to be activly top balanced. On the contratry. I believe if a pack is top balanced once, you will never have to do that again. Since the difference in aging speed, and therefor the increasing differences in capacity happens at the end of the discharge curve. That's why it's only a problem of a bottom balanced pack.



> Frankly I'm pretty convinced with the closely matched packs we can now get it doesn't really matter which way you balance the pack since they'll be almost as balanced at both ends.


The problem is that only time can tell. I keep on studying all scientific publications on the net. But not intensivly, because I hate them.


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## JRP3 (Mar 7, 2008)

Jan said:


> No, I don't mean that a top balanced pack regurlarly needs to be activly top balanced. On the contratry. I believe if a pack is top balanced once, you will never have to do that again. Since the difference in aging speed, and therefor the increasing differences in capacity happens at the end of the discharge curve. That's why it's only a problem of a bottom balanced pack.


I'm not following your logic. A top balanced pack means the cells will be discharged to different DOD every time. The smaller capacity cells will be more deeply discharged each time, aging them more quickly, decreasing their capacity and increasing their internal resistance more than the others. This will change their behavior on each cycle which should accumulate over time and probably lead to increasing imbalances when charging into the knee.


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## Jan (Oct 5, 2009)

JRP3 said:


> I'm not following your logic. A top balanced pack means the cells will be discharged to different DOD every time. The smaller capacity cells will be more deeply discharged each time, aging them more quickly, decreasing their capacity and increasing their internal resistance more than the others. This will change their behavior on each cycle which should accumulate over time...


Yes, if you use your pack to the limits this will happen. If you top or bottom balance doesn't matter. Or your weakest cells will be charged more in to the upper hyperbolic area, or they will be discharged in the lower hyperbolic area. That's not the point. The question is, if you loose your chosen point of balance.



> ...and probably lead to increasing imbalances when charging into the knee.


Consider the fact that capacity and power fade is concentrated at the end of the discharge curve, and hardly noticable in the main and top of the SoC. Only at very low temperatures it's noticable in the whole SoC spectrum.

While aging differently all cells will keep the same voltage from 100% to (lets say for example) 30% SoC. But below that, it starts to drift, while time passes by. In a top balanced pack you just stop discharging earlier over time. But the cells stay in sync at the top.

In a bottom balanced pack it is much more complicated. The faster aging cell drift faster away from that bottom balanced point, than others. So, while the 0% SoC kreeps slowly up, it doen't do that at the same speed for all cells. You will get imbalance.

Maybe I should make some graphs?


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## Jan (Oct 5, 2009)

Jan said:


> Maybe I should make some graphs?


Graphs are difficult. So, maybe in other words it makes more sense: 

In a top balanced pack the increasing difference in capacity will show at the bottom where there is already no balance in the first place.

In a bottom balanced pack this increasing difference in capacity will appear at the point where they where initially balanced.


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## ElectriCar (Jun 15, 2008)

I thought this thread was about battery boxes.


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## toddshotrods (Feb 10, 2009)

ElectriCar said:


> I thought this thread was about battery boxes.


 X2. Back to the box now!


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## ElectriCar (Jun 15, 2008)

So how thick would a battery box need to be to house my cells? They weigh 280lbs for 18 of them. I want to build a box to roughly 33x16" box in the back of my truck frame. 

I heard an interesting story from one of my employees today about his friend. He had a CF hood on his car and had an accident in the front. The hood RIPPED THE HINGES and flew off the car. The front of his car was crunched in but the hood had only scratches and needed touching up! 

I've worked with fiberglass before and it's not difficult at all. Nasty to sand etc but not difficult to make something. This stuff seems to be about the same type process except for some people "bagging" whatever that is and drying in an autoclave or oven.


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## DIYguy (Sep 18, 2008)

Sorry guys...but I only know how to work metal. Every time I use fiberglass, I end up with frayed bits stuck to my fingers and everything I touch.... I'm stickin with what I know (pun intended)  
Carbon fiber is for golf clubs and hockey sticks...  

I can calculate the strength of a welded structure... if I make something with this process.... It "might" look nice...but I would worry every time I hit a bump in the road... lol


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## JRP3 (Mar 7, 2008)

Jan said:


> While aging differently all cells will keep the same voltage from 100% to (lets say for example) 30% SoC. But below that, it starts to drift, while time passes by. In a top balanced pack you just stop discharging earlier over time. But the cells stay in sync at the top.


Voltage is only an indirect indicator of SOC. Top balanced cells that are developing higher internal resistance showing the same voltage as other cells while charging will actually be at a lower SOC to some degree. You can see this effect by cooling one cell down and charging it with another at room temp, the cool one will show "full" by voltage but if you let it warm up it will take more charge. This is an exaggeration of what might happen when top balanced cells with different resistance are charged.


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## JRP3 (Mar 7, 2008)

ElectriCar said:


> I thought this thread was about battery boxes.


It's not a real thread unless it wanders off topic at least once 
Maybe a mod could split off the battery discussion?


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## ElectriCar (Jun 15, 2008)

DIY did you see that framework that was holding up 500lbs spanning about 7'? It weighs less than 15lbs!


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## toddshotrods (Feb 10, 2009)

ElectriCar said:


> So how thick would a battery box need to be to house my cells? They weigh 280lbs for 18 of them. I want to build a box to roughly 33x16" box in the back of my truck frame.
> 
> I heard an interesting story from one of my employees today about his friend. He had a CF hood on his car and had an accident in the front. The hood RIPPED THE HINGES and flew off the car. The front of his car was crunched in but the hood had only scratches and needed touching up!
> 
> I've worked with fiberglass before and it's not difficult at all. Nasty to sand etc but not difficult to make something. This stuff seems to be about the same type process except for some people "bagging" whatever that is and drying in an autoclave or oven.


Figuring out what you really need is the tricky part. Is the box supporting the 280lbs vertically, just keeping them packaged neatly, or just for appearance? Two layers of carbon fiber, done right, is roughly equal to four layers of mat. I don't know if i would trust four layers of mat to support 280lbs in a street vehicle. Four layers of carbon fiber is going to start adding up, financially. Probably the ultimate compromise would be a box framed in aluminum angle, with foam-core carbon fiber panels bonded to the insides. You'd have two layers of pretty rigid carbon fiber (thanks to the foam core), with decent insulation properties (thanks to the foam core), and a lightweight aluminum frame to take the stresses of street driving. It should be purty too. Steel angle would work, as well, with a little weight penalty.

That hood experienced different stresses than your box would. One problem with composites is they can fracture when over-stressed. So, instead of seeing a bent part, there could be a stress crack starting that is invisible to you, until it finally reaches the point of no return.

Vacuum bagging is similar to sealing food in plastic pouches. You lay-up the part, seal it in a special bag, and use a vacuum pump to pull all the air out and add pressure to the cloth. It squezes out all the excess resin and air bubbles, leaving the perfect ratio for the highest strength possible. It also produces a nice finished surface, rather than the textured surface of the cloth you're left with on hand lay-ups. Sandwiching a mold between two male and female or flat surfaces also works, with pressure. That's how the SMC (sheet molded compound) parts on the newer production cars are made, and why they have smooth inner and outer surfaces.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> DIY did you see that framework that was holding up 500lbs spanning about 7'? It weighs less than 15lbs!


Yes very impressive. But I don't want to learn how to make it! lol (old dog syndrome)
I wanna make/improve my EV. There comes a point where u gotta leave some stuff alone. I designed and built my own house. That was 20 years ago. I'm guilty of being able to do every damn thing myself. Yes, I CAN do it.... but jeezuss I still have some stuff that I haven't finished and now I'm starting over re-modelling. new floors, windows, furnace etc etc.. Enough already. (end rant... sorry. . )


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## ElectriCar (Jun 15, 2008)

I'm sort of in the boat with you. I don't want to learn new tricks so I asked two of my guys today if they had ever done anything with it or knew someone who could. That's how I learned about the hood. I don't want to take the time to do it however if I find time I may start tinkering a bit. I still have to do my battery change out, fit the new equipment in and really wish I could just find someone to do it for me.


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## DIYguy (Sep 18, 2008)

OK, now I'm tickled pink. ))) I've looked countless times for a product to heat batteries that was simple, thin, inexpensive, easy to use and flexible in size etc for different applications... FINALLY.. I FOUND IT! damn.

http://www.bigappleherp.com/Flex-Watt-Heat-Tape?gclid=CLPqyqy676YCFdLLKgodBlKMAA

or 
http://beanfarm.com/index.php?cPath=1204_1205
http://www.beanfarm.com/heating/flexwatt_userinfo.pdf
http://www.beanfarm.com/heating/Flexwatt_connectors.pdf
http://www.beanfarm.com/heating/Flexwatt_parallel.pdf
http://www.beanfarm.com/heating/Flexwatt_Wiring.pdf

I think it's made by these guys.....http://www.calorique.com/iq.html Here is all the techy stuff.... http://www.calorique.com/techinfo.html

it comes in 3", 4" 11" and 17" wide and you can make it as long as you need. It comes on a roll. Of course if you are going to parallel some, you would likely want to match wattage.... and what I really like... it comes in 230volt


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## toddshotrods (Feb 10, 2009)

ElectriCar said:


> ...I don't want to learn new tricks...
> 
> ... I don't want to take the time to do it however if I find time I may start tinkering a bit...
> 
> ...really wish I could just find someone to do it for me.


The other option is to use the pre-made rigid composite panels. Just cut them and build your boxes. I'd offermy services if I still had a shop, lol! Now, all I can offer is a lot of hot air.


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## JRP3 (Mar 7, 2008)

Considering the pounding I've seen fiberglass boats take with about 1/4 inch layer of mat and roving I think you could build a pretty strong box with regular polyester resin and standard glass fabric. Mat gives little strength and is used to give a smoother surface so you can skip that. If you do it around a foam core you have built in insulation and added strength, though you probably want to switch to Epoxy resin unless you find a foam that doesn't dissolve from polyester. You could build a box out of blue insulating foam board and sheath it with epoxy and cloth, glass in some aluminum blocks to tap into for attachment points or something like that.


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## tomofreno (Mar 3, 2009)

Diy,
I think you said you plan to use aluminum sheet to spread out the heat. I guess you plan to adhere these heaters to the back and set it down on insulation in the box? Should work well. How do you plan to get the leads from the heaters out, and keep things from moving around/abrading as the car bounces down the road?

Watlow makes flexible heaters too, mostly Kapton-based:
http://www.watlow.com/products/heaters/ht_flex.cfm


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## DIYguy (Sep 18, 2008)

tomofreno said:


> Diy,
> I think you said you plan to use aluminum sheet to spread out the heat. I guess you plan to adhere these heaters to the back and set it down on insulation in the box? Should work well. How do you plan to get the leads from the heaters out, and keep things from moving around/abrading as the car bounces down the road?
> 
> Watlow makes flexible heaters too, mostly Kapton-based:
> http://www.watlow.com/products/heaters/ht_flex.cfm



Hey Tom. Yes, thanks for that.... I'll check it out. 
As for the other part... ya, I been thinking of using SM blue board on the bottom as I have some extra height based on current design. As you mention, I want to put some heating elements between the SM and either sandwiched or adhered to the back (underside) of the Al sheet. So, for cords and wires, the SM is thick enough to route passages for the underneath part. I'll have room at one end of the box also where I can make connections and run up/out of the box. 
The other thing is to make a space above the Al sheet and below the batteries for air movement that can channel up between the cells. I found some stuff that I will try...probably buy a piece of it today and show what I'm thinking. 
I haven't figured out how to make a seasonal vent to allow air into this space yet.. . still thinking on this.

BTW, regarding the fiberglass/carbon-fiber... I would likely be a lot more interested if I was doing a car where I wanted a nice trunk box molded into it. It's just with my truck + what I already have for boxes... I can't get too excited about it. The boxes I made took me a good deal of time WRT the whole build. Also, I'm pleased that I took the time to make them removable. So many guys with trucks weld everything in. I only welded in some new x-mbrs where needed. (my background is Welding Engineering in the automotive field and I have worked on the design and welding specs/drawings/procedures for many of the truck frames on the road today, so.... I kinda lean that way.)

Cheers.


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## rwaudio (May 22, 2008)

tomofreno said:


> Diy,
> I think you said you plan to use aluminum sheet to spread out the heat. I guess you plan to adhere these heaters to the back and set it down on insulation in the box? Should work well. How do you plan to get the leads from the heaters out, and keep things from moving around/abrading as the car bounces down the road?
> 
> Watlow makes flexible heaters too, mostly Kapton-based:
> http://www.watlow.com/products/heaters/ht_flex.cfm


Watlow does make very good heaters, however they are also very expensive. We used them for temperature control of gas lines in SOFC fuel cell test stands.

If it's rugged enough I think the heat tape would be the perfect budget solution for EV's.


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## DIYguy (Sep 18, 2008)

Here's the build up so far (samples). SM, Al ( I used a piece of SS ) plastic mesh stuff, battery. Of course the heat tape would be under the Al. 
Just so you get an idea of scale,.. that's 1/2" thick SM and that batter is a tiny 6 volt 2" x 2" x 6".


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## Overlander23 (Jun 15, 2009)

DIYguy said:


> Thanks Overoander. Do you have any pics?


Oops, sorry... didn't see this post until today. Here's a pic of the Farnham heaters taped to aluminum sheet using aluminum tape (the final actually has al tape completely around the heater pad edges, not just the corners). The leads all get paralleled together then crimped to 14 gauge wire. 

The aluminum sheet/heater combo sits on the black ionomer foam. The bottom shouldn't have to be that thick... heat will rise. I like the Ionomer because it's very resilient. You can't dent it. 

I don't have a good picture of what happens to the wiring, but I use plastic split conduit to route the wiring up the side of the battery box. I also used several layers of electrical tape on the sheet edge where the conduit bends around it to prevent the edge from abrading the conduit. The conduit itself should protect the wiring. I picked it up from Harbor Freight, but you can find it in pretty much any auto parts store in the electrical section. I also pack my cells in pretty tight so there's no real cell movement. 

I suppose you could make the system work off of the wall or the pack by running a 12V inverter off the DC-DC converter. Interesting idea. All up, my heaters will equal around 420 watts, if I recall correctly.

More details on my blog listed in my sig...


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## DIYguy (Sep 18, 2008)

Overlander23 said:


> Oops, sorry... didn't see this post until today. Here's a pic of the Farnham heaters taped to aluminum sheet using aluminum tape (the final actually has al tape completely around the heater pad edges, not just the corners). The leads all get paralleled together then crimped to 14 gauge wire.
> 
> The aluminum sheet/heater combo sits on the black ionomer foam. The bottom shouldn't have to be that thick... heat will rise. I like the Ionomer because it's very resilient. You can't dent it.
> 
> ...


Nice job on the Blog!  What did you use on the sides of your boxes? The ionomer insulation looks interesting. Good stuff by the look of it. How thick is yours?
I read somewhere else about a complaint on Kostov motor conductor routing/securing. Turns out, this is an issue. Thankfully your motor is still ok. This is a conductor from the brush circuit to the frame?...

cheers,
Gary


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## Jan (Oct 5, 2009)

JRP3 said:


> Voltage is only an indirect indicator of SOC. Top balanced cells that are developing higher internal resistance showing the same voltage as other cells while charging will actually be at a lower SOC to some degree. You can see this effect by cooling one cell down and charging it with another at room temp, the cool one will show "full" by voltage but if you let it warm up it will take more charge. This is an exaggeration of what might happen when top balanced cells with different resistance are charged.


OK, now I don't understand your logic.


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## JRP3 (Mar 7, 2008)

Cells may show the same voltage while nearing the end of charge but because they have different resistance they won't be at the exact same SOC. Actually if you initially top balanced using a long CV phase until current dropped near zero you would avoid that problem, never mind


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## DIYguy (Sep 18, 2008)

OK, now that I have my cells, I thought I would start to build up one of my boxes with the materials I've been collecting.

I started by riveting SS sheetmetal to the bottow. (no more wood). I then had to buff off most of the rivet head inside and smash them down flat. 
Next a piece of foam board in between the angle iron. 
Then another piece of foam board all over the bottom.
Then the Aluminum sheet. (not heat tape yet...but that is the plan, will be taped to the back of the aluminum.
Then I was going to use the plastic mesh stuff to allow air under the cells so I can draw it up through the passages....when I realized, that I don't need it. (Duh!) Cell spaces on bottom as well.

Can you beleive I made these boxes for other batteries. The fit is crazy good! lol 

The cells will be held together with 1/2 SS strapping and this will sit in the side groves taking up no more space. The seals will be on the end with space. I have few extra inches. I may even it up, well see. Anyways, here's some pics to start off...


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## DIYguy (Sep 18, 2008)

Oh yes, I wanted to mention... It's important that the boxes that sit under the truck box between the frame rails....are black. I don't want them easily seen when u bend over and look under... 

I plan to seal all the joints with either silicone or latex/silicone exterior caulk.


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## DIYguy (Sep 18, 2008)

I'll be posting some more pics this week... but basically, the boxes will be environmentally controlled. They will be ventilated by a thermostatically controlled fan that will draw air between all cells. A 40C snap switch mounted to copper connected to a terminal will control the fans. The fans will be the torsional ones...like an amplifier fan. Some boxes will get 12" fans, some 5 1/4". 
I have heat tape coming that is 6" wide. It will be powered by pack voltage but will be capable of running from grid power also if I chose. Again, temp controlled. There will be two temp sensors in the control circuit for these, one on top of the Al sheet (to control overtemp) and one further away, to get the upper ambient right. This is an important point particularly with this product.

I have all of the thermal sensors, 3 of the fans (12"), and the heat tape as well as the SSR to control them are on the way. Plan is to build up one box and play with it. Cycle it a bunch of times. Heat it up... cool it down, see how it responds. It's pretty straight fwd...so, I don't see any real issues.


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## ruckus (Apr 15, 2009)

Sounds like you have a plan.

I am wondering, does Lifepo4 really get hot enough at 1c to warrant such measures?

Don't you have to pull more like 5c to get them hot?

Is there data on this?

I also thought they performed better when hot -up to a point. My Thundersky chart shows them doing best at 131F! And having an operating temp up to 185F. 

What temp are you planning to have the fans come on?


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## tomofreno (Mar 3, 2009)

> I also thought they performed better when hot -up to a point. My Thundersky chart shows them doing best at 131F! And having an operating temp up to 185F.


 Really? The CM prof said not to exceed 60 C which is about 140 F, because the solvent starts to breakdown and form a resistive deposit on the anode.


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## DIYguy (Sep 18, 2008)

ruckus said:


> Sounds like you have a plan.
> 
> I am wondering, does Lifepo4 really get hot enough at 1c to warrant such measures?
> 
> ...


Yes, Tom is correct. Somewhere between 50 and 60C the electrolyte solvent breaks down resulting in reduced capacity and significant reduction to life expectancy. The increased resistance is due to the electrodes becoming coated with things like lithium carbonate. 
Even when this critical temp is not reached, higher temps = shorter life.

The other significant issue, particularly for me because I will be going BMS-less, is the temp delta between cells. I have multiple battery boxes in my truck and I want to keep their temps relatively the same. Significant temp differences can cause reduced capacity on the colder ones and potentially some amount of drift over time.

I will be pulling 5C on occasion... 

Edit, to answer your question, I will monitor the terminal voltage and at 40C, my fans will start. This will be a control circuit in each box.


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## ElectriCar (Jun 15, 2008)

DIYguy said:


> I'll be posting some more pics this week... but basically, the boxes will be environmentally controlled. They will be ventilated by a thermostatically controlled fan that will draw air between all cells. A 40C snap switch mounted to copper connected to a terminal will control the fans. The fans will be the torsional ones...like an amplifier fan. Some boxes will get 12" fans, some 5 1/4".
> I have heat tape coming that is 6" wide. It will be powered by pack voltage but will be capable of running from grid power also if I chose. Again, temp controlled. There will be two temp sensors in the control circuit for these, one on top of the Al sheet (to control overtemp) and one further away, to get the upper ambient right. This is an important point particularly with this product.
> 
> I have all of the thermal sensors, 3 of the fans (12"), and the heat tape as well as the SSR to control them are on the way. Plan is to build up one box and play with it. Cycle it a bunch of times. Heat it up... cool it down, see how it responds. It's pretty straight fwd...so, I don't see any real issues.




Are you going to make it easy for us by posting part numbers etc on the thermostats, heater and fans?
Are the thermostats built in to the fans?
Do the fans pull in fresh air all the time or are provisioning for winter ops with recirc capacity?
My batteries are being delivered Tuesday.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> Are you going to make it easy for us by posting part numbers etc on the thermostats, heater and fans?
> Are the thermostats built in to the fans?
> Do the fans pull in fresh air all the time or are provisioning for winter ops with recirc capacity?
> My batteries are being delivered Tuesday.


Oh yes, for sure... I will post up all the goodies for anyone who want's to follow me down the pier... lol

No, I ordered the thermostats from Digikey. Pic of one mounted below.

The thermostats will be in the 12 volt control circuit for the fans. I have a pic of the 12" ones, I still have to get the 5 1/4" ones.

I really can't see the benefit to recirc. I will pull in fresh air and it will be drawn between all the cell. I believe these ribs on the prismatics are primarliy for cooling. I first thought it was more for rigidity.


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## ElectriCar (Jun 15, 2008)

Great. I'm keenly interested in keeping them warm but I'm seriously doubting they'll be getting warm as normal cruise will be in the .3C area. However if I take a trip on the interstate which will happen with the new range there could be steady .5C with bursts to 1-1.25C on hill climbs. 

Cold temps though will get me in the winter because of the low C driving conditions won't create much heat I suspect and will be parking outdoors except for when home in the garage.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> Great. I'm keenly interested in keeping them warm but I'm seriously doubting they'll be getting warm as normal cruise will be in the .3C area. However if I take a trip on the interstate which will happen with the new range there could be steady .5C with bursts to 1-1.25C on hill climbs.


...and u will never put ur boot into it... Doesn't the temp get rather warm in the summer? 35C?... doesn't take much to get them warmer with high ambient.


ElectriCar said:


> Cold temps though will get me in the winter because of the low C driving conditions won't create much heat I suspect and will be parking outdoors except for when home in the garage.


I will have some neat stuff to show for heating also. 

Hope u get ur batts soon!


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## JRP3 (Mar 7, 2008)

Even in the heat and normal driving between 1-2C with occasional higher bursts my cells never felt that much warmer than ambient.


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## ElectriCar (Jun 15, 2008)

That's what I wanted to hear JRP. I didn't think they would with the extremely low IR of the newer batteries. Another reason to purchase larger cells and use higher voltages.


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## DIYguy (Sep 18, 2008)

JRP3 said:


> Even in the heat and normal driving between 1-2C with occasional higher bursts my cells never felt that much warmer than ambient.


Yes, thanks for that. Good to know. Perhaps I won't need the cooling, however, I would like to keep the boxes closed up this time which may trap a lot of the heat. I left them open on the top with my AGM's and found a lot of road dirt on top of them.

I also have a heavy truck with a Soliton1...  

I'm also looking at cheap ways to get temp monitoring in each box... so I can watch it. Or maybe I'll just buy one of the cheap indoor/outdoor wireless ones and move it from box to box, to get the info.


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## JRP3 (Mar 7, 2008)

Good point, mine are in open racks.


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## ElectriCar (Jun 15, 2008)

I'm ready to build my new boxes. I'm no mechanical engineer and *haven't found any span/weight charts to help me select the optimum materials to minimize weight* yet yield a strong rack that won't sag under the G forces of dips in the road etc. 

The old racks I built from 1.25" angle iron with 1/8" flat steel welded underneath to support the batteries at their edges. 

So far I've removed about 180 lbs including racks and 17lbs of vacuum motor, tank, brake booster and switch. I still have the back rack to remove which I suspect weighs around 40 lbs. I'm hoping I can build the new racks and do it with light enough materials so that I can keep the weight savings around 180-250 lbs. I'm also likely replacing the leaf springs with composite springs to shave off maybe 40-70 lbs but that's just a guess there.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> I'm ready to build my new boxes. I'm no mechanical engineer and *haven't found any span/weight charts to help me select the optimum materials to minimize weight* yet yield a strong rack that won't sag under the G forces of dips in the road etc.
> 
> The old racks I built from 1.25" angle iron with 1/8" flat steel welded underneath to support the batteries at their edges.
> 
> So far I've removed about 180 lbs including racks and 17lbs of vacuum motor, tank, brake booster and switch. I still have the back rack to remove which I suspect weighs around 40 lbs. I'm hoping I can build the new racks and do it with light enough materials so that I can keep the weight savings around 180-250 lbs. I'm also likely replacing the leaf springs with composite springs to shave off maybe 40-70 lbs but that's just a guess there.


I just typed a lengthy reply... and lost it. Maybe I'll take a stab at it again later.... geesh. I hate laptops....come to think of it... I hate PC's too... lol


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## ElectriCar (Jun 15, 2008)

LOL I know. Been there done that got a T-shirt!  And it ain't funny when you realize you just wasted all that time. Now I copy any lengthy post before hitting submit.


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## DIYguy (Sep 18, 2008)

I was basically typing away about the good, the bad and ugly of making boxes out of Aluminum. Sounds like you are mod'ing your steel ones anyways...so I won't bother. My boxes were designed to hold lead acid and are significantly lighter than yours by the look of it. That makes mine, and to a greater extent yours, over designed for Lithium. Not such a bad thing.... but, extra weight.... you could spend some time drilling holes..


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## ElectriCar (Jun 15, 2008)

No I cut the steel boxes out. Scrap. They weighed about 35lbs each! I'm planning on aluminum boxes from thin plate aluminum. The boxes by the drive shaft will hold about 210 lbs of batteries each. The one in the back will hold about 330. 

The plan is for a sealed enclosure with heat and thermostat. If I find them getting warm I'll add a fan and ventilation holes.

So go ahead with your post but copy it before you hit submit! lol.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> No I cut the steel boxes out. Scrap. They weighed about 35lbs each! I'm planning on aluminum boxes from thin plate aluminum. The boxes by the drive shaft will hold about 210 lbs of batteries each. The one in the back will hold about 330.


Define "thin". Thin sheet metal Al boxes work great when they are sitting on another surface. If they are going to be suspended by attachment points, there needs to be many of them and possibly reinforcement depending on sheet thickness.
Sheet structures struggle at spanning any distances also... and keeping their lines.
What welding process will you use? How are your welding skills?
Do you have any thoughts/plans about the galvanic action?



ElectriCar said:


> The plan is for a sealed enclosure with heat and thermostat. If I find them getting warm I'll add a fan and ventilation holes.
> 
> So go ahead with your post but copy it before you hit submit! lol.


The jury may be still out on ventilation requirements since it depends on many factors. That said, if they will be sealed, you will likely need some kind of ventilation in the summer/warmer months. Perhaps it doesn't need to be forced, but some way to let the heat out.

Since my boxes are relatively light, I will end up with a composite structure. My angle is 1" and some 3/4". I did drill one of them full of holes also just for the heck of it.


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## ElectriCar (Jun 15, 2008)

Brother I was hoping you had already blazed a trail before me about this! Galvanic reaction? Never crossed my mind. I used aluminum tubing in my original build in some places. It's not an issue that I can see. I've seen aluminum bolted to steel in industry for years and it's never been a problem that I've seen.

Re spanning, I was thinking of having a frame built with aluminum angle and weld sheet aluminum to that. I have some concerns about it flexing too much allowing the pack to flex. That's not good for the battery posts and could destroy cells due to stresses on the terminals with lateral pressures. 

I have a friend who is going to do the welding and help with the fabrication. Whenever I tried that, and I've tried a LOT, I only manage to make aluminum blobs or blow holes in it. Must not have been holding my mouth right or something.  Welding steel and iron was very easy to learn. I gave up on aluminum. 

I was thinking of like a 1/8" sheet and cut the sides, bottom and top from that. To support the bottom I think there will need to be a piece of square tubing or angle to prevent sagging and stiffen it. The "side" racks along the drive shaft will be about 36" on the longest run. It will be supporting half of two rows of 5 batteries and one row of 4 allowing clearance of the diff. One end will be about 12" and the other end split with about 8", the width of two batteries and a corner cut out with the last piece of that end about 4" if you can visualize that. The side opposite the 36" side will be about 29" with another piece about 7" at the cutout corner. These numbers are close, not exact.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> Brother I was hoping you had already blazed a trail before me about this! Galvanic reaction? Never crossed my mind. I used aluminum tubing in my original build in some places. It's not an issue that I can see. I've seen aluminum bolted to steel in industry for years and it's never been a problem that I've seen.


Typically, when Al and steel are fastened together, there is a coating of some kind on one of them or a layer of something. Just make sure your steel has a high quality paint on it and it'll be fine.


ElectriCar said:


> Re spanning, I was thinking of having a frame built with aluminum angle and weld sheet aluminum to that. I have some concerns about it flexing too much allowing the pack to flex. That's not good for the battery posts and could destroy cells due to stresses on the terminals with lateral pressures.


Yes, this is the right idea. If the frame is strong enough, the rest needs to be little more than a skin to keep out the elements. I would recommend bolting the box into place and do it to the frame obviously. Think of how wide the batteries are and if you put support along these interface lines, you will be in good shape. Design the Al frame so it will hold all the batteries without a skin... this is the best way to visualize it. If your skin is welded in place, you shouldn't need any cross bracing then.



ElectriCar said:


> I have a friend who is going to do the welding and help with the fabrication. Whenever I tried that, and I've tried a LOT, I only manage to make aluminum blobs or blow holes in it. Must not have been holding my mouth right or something.  Welding steel and iron was very easy to learn. I gave up on aluminum.


 Yes, it can be a challenge. As long as you have a guy who knows. GMAW I assume?


ElectriCar said:


> I was thinking of like a 1/8" sheet and cut the sides, bottom and top from that. To support the bottom I think there will need to be a piece of square tubing or angle to prevent sagging and stiffen it. The "side" racks along the drive shaft will be about 36" on the longest run. It will be supporting half of two rows of 5 batteries and one row of 4 allowing clearance of the diff. One end will be about 12" and the other end split with about 8", the width of two batteries and a corner cut out with the last piece of that end about 4" if you can visualize that. The side opposite the 36" side will be about 29" with another piece about 7" at the cutout corner. These numbers are close, not exact.


I think the sheet thickness can be a function of the frame strength. If the frame can hold all the batteries, the sheet can be lighter. If you make the sheet thicker, the frame can be lighter EXCEPT the bottom.... if wider than one battery size.
Of course we aren't using modeling software and running dynamic load simulations...so it has to be a bit over designed.


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## DIYguy (Sep 18, 2008)

I was hoping to have my "test box" done this week... however, I haven't received my SSR's or my heat tape yet. 

Here are a couple progress pics though. You can see my fan mounted on the one side.


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## ElectriCar (Jun 15, 2008)

Is the box framed with steel or aluminum? It looks about like my old steel ones. Are the sides tin?


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> Is the box framed with steel or aluminum? It looks about like my old steel ones. Are the sides tin?


No, the frames are all steel. Similar to yours, only bit lighter angle. I used 1x1x1/8 and some 3/4 also. I won't be doing any Aluminum frames. They were an efficient design for lead...just strong enough... a bit overkill for Lifepo but not too bad though, they aren't all that heavy. Other materials are SS and Al sheet metal. Long sides are foam board right now. Not sure If I will cover them or not. They are sized very well for my batts. Minimal mods required... and they install with SS fasteners. 
Al is 1/3 the weight of steel. Depending on grade, it often needs to up-sized 50% for structural applications. There are still weight savings to be had though.


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## DIYguy (Sep 18, 2008)

I received my heat tape yesterday. This stuff is all that I had hoped for and more. I can't imagine a better way to incorporate heaters into a box. Apparently, these guys have done a lot of battery heating applications including something with Ford apparently. Anyways, I haven't received my SSR yet, but I installed a strip in one of my boxes and tried it on 120vac (while monitoring)... it worked great. This piece is about 2 feet long and draw was 0.3 amps so, about 36 watts on wall power. It's super easy to work with, just cut it with scissors and while there are proper fasteners, I just soldered leads onto the bus strips. I just used aluminum foil tape to fasten it on Al heat spreading sheet.


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## ElectriCar (Jun 15, 2008)

That's awesome! And with that low power it should last too. 

I read the book on Calb batteries last night. Said to use a 3mm rubber mat under to help absorb bumps. Are you doing that? It also said they could be charged to 3.9V but stop at that point. That makes me feel better about my setup. I'll likely be stopping well short of that.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> That's awesome! And with that low power it should last too.


 There isn't anything to go wrong/fail unless it's abused I think. When powered and in open air, it doesn't really feel like it gets all that hot (on 120vac). When it's "trapped" and attached to the Al sheet, the sheet gets quite hot. It is important to use temperature control in these cases. Recommendation is to have some kind of sensor on or close to element to prevent over heating from longer duration on-times with high power. A thermostat is also recommended on higher power applications. The reptile guys just use an incandescent light dimmer.



ElectriCar said:


> I read the book on Calb batteries last night. Said to use a 3mm rubber mat under to help absorb bumps. Are you doing that? It also said they could be charged to 3.9V but stop at that point. That makes me feel better about my setup. I'll likely be stopping well short of that.


Yes, I read that also. I have two layers of 5mm foam board on the bottom, which will insulate and provide the dampened ride.


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## ElectriCar (Jun 15, 2008)

I went back and looked to find the data on your heat tape but didn't find it. And where did you get that rubber expanded metal looking mat? 

I just ordered 4 Rotron 12V 120mm fans for my box. I'm thinking of installing them in the top and making some type of perforations for air to get in the box and travel through the battery slots. The battery manual says to power the fans at 104F and cut back on controller power at 122F so I need to get some thermostats for that too.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> I went back and looked to find the data on your heat tape but didn't find it. And where did you get that rubber expanded metal looking mat?


The heat tape was a PITA to try and get here in Canada. I ended up tracking down the company who makes it called Calorique and they now sell direct, which is kewl. http://www.calorique.com/ The site has a lot of info, but doesn't list/show all their products. They will design whatever you need around their product as they have a lot of different ones. The fellow I delt with there actually sent me this roll (enough for my whole pack) for free!!!!!! Can you believe that? PLEASE don't bug him for free stuff, I don't want to cause him greif... lol He was so nice to me. I wanted a 6 inch wide product that will work with 200 volts dc and still function on 120vac albeit at a lower power. Anyways, I will post the model number of it when I look it up. edit... model # HST7-26W120V
As for the plastic stuff that looks like expanded metal, it's a flooring product, bought it at Rona. I realized I didn't needed when I saw how the spaces were across the bottom.



ElectriCar said:


> I just ordered 4 Rotron 12V 120mm fans for my box. I'm thinking of installing them in the top and making some type of perforations for air to get in the box and travel through the battery slots. The battery manual says to power the fans at 104F and cut back on controller power at 122F so I need to get some thermostats for that too.


I did some tests to see how the air would flow around the cells and through the passages. It wasn't too scientific.... but revealing. First, I would recommend using the squirrel cage type of rotary axial fan. (the 12 volt ones are often called "cross flow fans and were used for amplifier cooling) This kind of fan can draw at a higher static pressure which is needed to get air to move through smaller passages. It's the same for forcing air through my motor. The squirrel cage fan for boat bilges like what I used work best. This is why they use this type of fan in your furnace blower... the higher static pressure is required to get the air flow through all the pipes and longer passages. We used this type of fan in industry also for smoke extraction in welding lines....with long pipes and smallish vents (albeit with 200 hp motors...lol) Same reasoning, we learned early on that the other fans couldn't draw the smoke away... too many losses. 
Also, you need some other passages besides the spaces created by the ribs.... like an inch across the top at least. Otherwise you will find the fan just wont draw enough air. When you restrict air flow to a fan, the current (load) drops as the fan "free wheels" more. The most energy is used when a fan is drawing the most air it can.


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## helluvaengineer96 (Oct 8, 2010)

*Has anyone tried thermoelectric pads/elements?*

I remember playing with these back in the early 90's they were very in-efficient since the cool side and the hot side were so close, most you could hope for was a few degrees. I do remember stacking them for decent results.

The problem with using these to cool the batteries is how to get contact with the surface of the battery on one side and contact with a heat dissipating material on the other.

What's a thermoelectric pad? If you have a cooler that plugs into your cars outlet to stay hot or cold it has a thermoelectric pad in it. With out getting into the details the pad pulls energy (heat) from one side and dumps it on the other. The polarity of the voltage decides which side is the hot side and which is the cool.

Here is my first thought on how to deploy these devices:

Battery----thermoelectric element----Alum.------thermoelectric element----Battery...repeat.

The Alum would act as a heat sink allowing the heat to leave... Thicker the better. You would not want the pack to be too tall.

Thoughts?

Here is link to vendor... Wow they have improved a lot. Looks like they can produce a delta temperature of 75 degrees F.. Wow.
http://www.crystalltherm.com/thermomodules_h.html

Also here is picture of how they could be used with the prismatics.


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## DIYguy (Sep 18, 2008)

*Re: Has anyone tried thermoelectric pads/elements?*

Thanks for the post. It's an interesting topic. I've seen it mentioned before...but not too much detail application discussion. Not aware of anyone using this technology for battery cooling. I certainly think it has potential however, the key would be an efficient and cost effective design. 



helluvaengineer96 said:


> The problem with using these to cool the batteries is how to get contact with the surface of the battery on one side and contact with a heat dissipating material on the other.


 Yes,I think u are right. 




helluvaengineer96 said:


> Here is my first thought on how to deploy these devices:
> 
> Battery----thermoelectric element----Alum.------thermoelectric element----Battery...repeat.
> 
> ...


First thought is that the cooling components are taking up as much room as the batteries. This isn't really practical. I suspect the cost would be rather high also. In an application needing very high heat dissipation, perhaps something could be done. Perhaps if the battery box was lined with these and head sinks protruding outwards...?

I guess the thing is, for the avg joe, heat isn't a huge problem. Most commuter designs draw at low power and the resistance of these cells is quite low. I think most will never even need cooling. My application is in a truck. That said, all battery boxes are outside the cabin. Under the bed and under the hood. I want to close in these boxes to keep things clean and protected. This in itself causes a little concern and therefore my desire to have some airflow. Also, living in Canada, I want to heat them for cold days and therefore enclosed, insulated boxes are required. I could have a seasonal "change-over" ...which is still an option.

Thanks for the ideas though. This is a kewl bit of technology.


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## helluvaengineer96 (Oct 8, 2010)

*Re: Has anyone tried thermoelectric pads/elements?*

DYI... agree not terribly practical especially at the prices I've been seeing, around $20 for a little over a square inch.

Was thinking more along the lines of a way to charge batteries super quick. Not so much for cooling during discharge, don't want to reduce range. Efficiency won't matter much since AC power is available during charging.

My project has not progressed to the point of buying batteries yet. But from what I've read and experience with lead acids going into thermal run-a-way, the Li cells can get pretty hot if you load them with a bunch of charge current. 

The use of space is a big negative. I've designed my battery pack to use every square inch for just the batteries (in the Fiero's gas tank area).. So I definitely can't try on my current EV.

Yup you definitely have different environmentals up there. Not sure how you folks do that. Use to spend a good amount of time in Ottawa, but I always lucked out and it was in the summer time. 

My EV goals aren't for the practical but a test bed to experiment on and have fun with... So sometimes my posts can be off the wall.

Speaking of off the wall.... The same device can be used to generate voltage. Not sure how much heat the controllers put out (shouldn't be very much since they need to be very efficient). But if there is a component that generates a lot of heat then these could be used to recoup some power.

*BTW*:I think you want to keep all batteries near the same temp so they all charge or discharge at the same rate... so if the thermoelectric elements are used they should be evenly distributed.


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## DIYguy (Sep 18, 2008)

*Re: Has anyone tried thermoelectric pads/elements?*



helluvaengineer96 said:


> *BTW*:I think you want to keep all batteries near the same temp so they all charge or discharge at the same rate...


I agree. This is one of my goals.


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## DIYguy (Sep 18, 2008)

I decided to lighten up the box a little. More in line with the new load.


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## JRP3 (Mar 7, 2008)

You know you can buy angle iron like that with holes already in it?


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## helluvaengineer96 (Oct 8, 2010)

DIYguy said:


> I decided to lighten up the box a little. More in line with the new load.


Looks cools.. Hate to date myself but it reminds me of an erector set (sp?).


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## DIYguy (Sep 18, 2008)

JRP3 said:


> You know you can buy angle iron like that with holes already in it?


Gee thanks JRP.... lol. Ya, well.... I was bored waiting for other stuff to finish up. As you know...it was made to suit the heavy old lead, and I didn't want to start over.


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## ElectriCar (Jun 15, 2008)

That shoud really help lighten it up. Looks good too! I'll pick up the bottom of my rack tomorrow and start installing it.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> That shoud really help lighten it up. Looks good too! I'll pick up the bottom of my rack tomorrow and start installing it.


Looking fwd to see pics of yours.


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## ElectriCar (Jun 15, 2008)

DIY, you said you were going to construct the box with heaters and test them out so how's the testing going? I'm working to get my box installed and am thinking of using your design.  We went with 2x2x3/16 steel instead of aluminum.  I really wanted to use aluminum but my friend picked up the steel and welded it up for me. 

Anyway I was curious how the heat tape was performing? Are you using the SSR relay from Newark Electronics that Overlander is using to control the heaters? I would think the snap switches would handle that small amount of current directly. Also if you have the part numbers handy on the switches that would be awesome. 

So what do you think of this? The box is roughly 40x38. It has three 2x2" cross braces underneath with 8 inch gaps between them. I'm thinking of using a 1/16" steel sheet as the bottom with 1/2" insulation on that with a layer of radiant barrier on it, heat tape on the RB side, then 1/8 aluminum spreader and finally if I can find it, a thin rubber mat. Also going to enclose it with a 40x38x1/8 gasketed removable aluminum top. 

The fans I got are designed to operate at a higher static pressure than normal so I'm fairly confident they will work with enough holes! I'm thinking of using the holes in the bottom that I drilled in the angle along with more holes drilled in the bottom sheet and insulation as a means to feed fresh air for the fans in summer. Thinking of a sliding cover underneath that will cover the holes for winter use sort of like you have in the US for crawl space vents.

For the sides, either aluminum sheet or tin riveted on to the steel frame.


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## DIYguy (Sep 18, 2008)

Hey Electric,

Sorry for the delay. Been a busy week and I've been waiting for my relays.... they just arrived yesterday. I bought these Futek or Fotek or whatever they are called. I had to wait for them but they were only like, $11 each or something like that. Control 3 - 32vdc and power side 5 - 220vdc. This depends on what you plan to use, as I am using battery pack power. You can buy Crydom relays if you like, just match the specs to your application. I did test it last night by putting a switch in the control power side. 

I bought three different switches. One is a 40C N/O switch for the fan. This is what you read about the temp in the booklet. At 40C it will close and allow 12v to the fan. This is DIGIKEY P/N 317-1505-ND.

For the heater switches, I bought two. One will reside on the Al heat spreader and it is 35C P/N 317-1503-ND... this is a N/C switch. The other will be further away and is also a N/C switch for 20C 317-1495-ND. I'm not sure that these two are exactly right yet... but should work ok. All of these switches are "Faston". I do have manufacturer's P/N's if you need them. For a picture, just look on earlier pages. 

I am looking forward to your build also. Will check in later tonight.


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## ElectriCar (Jun 15, 2008)

Awesome, just ordered the switches. Time is $$$ nowadays! Now I need to order the heating tape.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> DIY, you said you were going to construct the box with heaters and test them out so how's the testing going? I'm working to get my box installed and am thinking of using your design.  We went with 2x2x3/16 steel instead of aluminum.  I really wanted to use aluminum but my friend picked up the steel and welded it up for me.


I'm a bit surprised honestly, about the size of angle you are using. I know all of your batteries are going in one box... but that angle is almost 2.5 lbs per foot isn't it?? One of my battery boxes for lead was about 28" square and held well over 800 lbs and it was fab'd out of 1x1x1/8. It's all about the design tho. You definitely shouldn't have any issues with strength.


ElectriCar said:


> Anyway I was curious how the heat tape was performing?


I've only just played with it. I powered it several times and left it in my box for an hour turned on, without thermostats to see if it was gonna melt my insulation. It didn't. I think it is gonna be perfect.


ElectriCar said:


> So what do you think of this? The box is roughly 40x38. It has three 2x2" cross braces underneath with 8 inch gaps between them. I'm thinking of using a 1/16" steel sheet as the bottom with 1/2" insulation on that with a layer of radiant barrier on it, heat tape on the RB side, then 1/8 aluminum spreader and finally if I can find it, a thin rubber mat. Also going to enclose it with a 40x38x1/8 gasketed removable aluminum top.


I can't quite picture it. Are the braces from corner to corner? 
I fount that the Al sheet can be quite thin. 20 gauge is fine.


ElectriCar said:


> The fans I got are designed to operate at a higher static pressure than normal so I'm fairly confident they will work with enough holes! I'm thinking of using the holes in the bottom that I drilled in the angle along with more holes drilled in the bottom sheet and insulation as a means to feed fresh air for the fans in summer. Thinking of a sliding cover underneath that will cover the holes for winter use sort of like you have in the US for crawl space vents.


I think it should work ok. The fans u have probably wont draw much through the passages, but they will move some air... and that is probably all that is required with our application. I would leave some other route for air to move other than the spaces created by the battery ribs.
[/quote]


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## ElectriCar (Jun 15, 2008)

After all is said and done including heaters, spreader, top and framework, it will weigh in at about 105lbs, still 65lbs lighter than the old boxes and braces I welded in! I'll take a picture the next time I'm there and post a photo of the bottom with the sheet steel welded in. I'd like to work on it tomorrow but I have some work at home that needs doing.

The bottom is all steel but the sides. top and remaining framework will all be aluminum with aluminum sides riveted to the frame like Overlander did. It's almost ready to lay the batteries in!


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## tomofreno (Mar 3, 2009)

DIY, Any update on your battery cooling system? Fans you ended up using, cost, source? Thermostats work out ok? Getting warmer here, need to start thinking about adding fans to mine as last year the cells were getting up to around 110 F after long hills in 100+ F ambient.


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## DIYguy (Sep 18, 2008)

tomofreno said:


> DIY, Any update on your battery cooling system? Fans you ended up using, cost, source? Thermostats work out ok? Getting warmer here, need to start thinking about adding fans to mine as last year the cells were getting up to around 110 F after long hills in 100+ F ambient.


Hi Tom. Everything is working out well. I don't have any driving tests done, but in the shop the heater, thermo switches and fans work well. The fans were picked up from an electronics surplus place. Just google "cross flow fan".
A 10 degree delta isn't bad u know. 100 F is pretty hot 4 sure. You may want to go with a more substantial fan like a marine bilge fan. Not the in-line ones though, the squirrel cage design. They have a higher static. Like what is often used for motor blowers. 

Cheers
Gary


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## dtbaker (Jan 5, 2008)

110F doesn't sound too scarey. I don't think the internal goop starts having problems till around 150F, right?

d


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## dtbaker (Jan 5, 2008)

DIYguy said:


> ...I bought these Futek or Fotek or whatever they are called. I had to wait for them but they were only like, $11 each or something like that. Control 3 - 32vdc and power side 5 - 220vdc.


these look really cool... and not too expensive! How do you think they will handle the initial inrush of current when the heaters are cold?

please post source...


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## tomofreno (Mar 3, 2009)

110F doesn't sound too scarey. I don't think the internal goop starts having problems till around 150F, right? Not according to the CMU prof's statement of 50 to 60 C causes breakdown of the electrolyte resulting in loss of capacity and increase in resistance. The 60 wouldn't be worrisome, but 50 C is. We've had 110 F ambient here, and they have higher in Phoenix.


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## dtbaker (Jan 5, 2008)

tomofreno said:


> 110F doesn't sound too scarey. I don't think the internal goop starts having problems till around 150F, right? Not according to the CMU prof's statement of 50 to 60 C causes breakdown of the electrolyte resulting in loss of capacity and increase in resistance. The 60 wouldn't be worrisome, but 50 C is. We've had 110 F ambient here, and they have higher in Phoenix.


hhhmmm, ok I can see the concern. 50 deg C = 122deg F and if the outside of the case is getting up to 110F, ya gotta worry about what the inside of the case is....

however, thundersky lists 85 deg C as upper limit, and CALB shows 55 deg C AMBIENT... hard to tell what real internal temp limit might be...


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## DIYguy (Sep 18, 2008)

dtbaker said:


> these look really cool... and not too expensive! How do you think they will handle the initial inrush of current when the heaters are cold?
> 
> please post source...


Hey Dan, I'm pretty sure it was here. http://www.satistronics.com/solid-state-relay-dc-to-dc-ssr10dd-10a-220vdc_p2224.html 

Looks like the price has come down also. Less than 7 bucks. I think I paid 11 something, but shipping was free. I don't see any issue with in-rush. Current is pretty low. I picked the 10 amp ones and I will be drawing a fraction of an amp.


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## dtbaker (Jan 5, 2008)

looks like a great little relay for heater on/off and the battery box heatline and or fan on/off. The heater I am a little worried about as the 1500watt variety have a pretty big amp spike in the first second or two as they heat up.

how about thermistats, themistors and that sort of thing to sense to control the relays at set temps? you have a good line on those?


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## ElectriCar (Jun 15, 2008)

dtbaker said:


> hhhmmm, ok I can see the concern. 50 deg C = 122deg F and if the outside of the case is getting up to 110F, ya gotta worry about what the inside of the case is....
> 
> however, thundersky lists 85 deg C as upper limit, and CALB shows 55 deg C AMBIENT... hard to tell what real internal temp limit might be...


Here's what's in the Calb manual. 
40C (104F) Initiate cooling
50C (122F) Controller to limp mode
55C (131F) Shut down the controller!


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## dtbaker (Jan 5, 2008)

ElectriCar said:


> Here's what's in the Calb manual.
> 40C (104F) Initiate cooling
> 50C (122F) Controller to limp mode
> 55C (131F) Shut down the controller!


good information... but measured WHERE? 

thermocouple stuck to terminal when internal heat might conduct? 
to case at top in the middle somewhere?
... I am wondering what the suggested sensor placement is that would most accurately represent temp issues internally.


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## ElectriCar (Jun 15, 2008)

Well dt you know I don't think you can measure the internal temp but I've just placed thermostats inside an insulated box. If the temp rise is slow,which should be the case with me since I'll be drawing only .3-.5C with normal cruise, the box temp should be slightly lagging but very close to the battery temp. Besides I don't anticipate any real heat build up. More than likely the only time it could become an issue is when setting in the sun on a 100 degree day.


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## dtbaker (Jan 5, 2008)

I am not worried about the low C heat, I don't think hardly any is generated.  What I want to catch as quickly as possible is sudden spike after short burst accellerations. I am thinking the best way to do that is a thermocouple ON either one of the terminals where the internal temp would conduct pretty rapidly, or on the outside of the case in contact w/ case. There would be some lag due to speed of heat transfer, but would give a pretty good idea of internal temp pretty quickly....

I am jut wondering if anyone (factory?) has any more specific data showing 'with thermocouple in X location, lab testing showed internal temp was Y, and thermocouple registered z after W seconds....'


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## JRP3 (Mar 7, 2008)

Since the terminal is a direct connection to the inside of the cell and metal is pretty good at heat transfer I'd think a terminal is the best place to measure internal temperature.


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## dtbaker (Jan 5, 2008)

JRP3 said:


> Since the terminal is a direct connection to the inside of the cell and metal is pretty good at heat transfer I'd think a terminal is the best place to measure internal temperature.


thats what I'm thinking... I got some cheap 'remote' thermometers that have pickups with a cord long enough I can run them to terminals or maybe on the busbar as close as I can.

what do you think would be a good adhesive to stick'em on, but not interfere w/ heat transfer? I was thinking silicone caulk, but afraid it would insulate. Perhaps just a wrap around with the metal-foil duct tape?


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## JRP3 (Mar 7, 2008)

As long as the foil won't conduct electricity somewhere you don't want, and as long as the adhesive can handle the heat, which it probably can. A thin layer of crazy glue or epoxy might work as well.


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## tomofreno (Mar 3, 2009)

> Since the terminal is a direct connection to the inside of the cell and metal is pretty good at heat transfer I'd think a terminal is the best place to measure internal temperature.


Yeah, like this: 
http://www.diyelectriccar.com/forums/showpost.php?p=229687&postcount=77


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## tomofreno (Mar 3, 2009)

> Here's what's in the Calb manual.
> 40C (104F) Initiate cooling
> 50C (122F) Controller to limp mode
> 55C (131F) Shut down the controller!


So in Phoenix in July and August you would be running in limp mode much of the time. In Death Valley you wouldn't be operating at all (127 F typical when they run the 100+ mile race from there to Whitney Portal at 8000+ ft elevation). When it is 110 F like it as been here a few times, it wouldn't take much to put you in limp mode.


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## dtbaker (Jan 5, 2008)

tomofreno said:


> So in Phoenix in July and August you would be running in limp mode much of the time. In Death Valley you wouldn't be operating at all (127 F typical when they run the 100+ mile race from there to Whitney Portal at 8000+ ft elevation). When it is 110 F like it as been here a few times, it wouldn't take much to put you in limp mode.


so if in phoenix, you'd have to duct A/C refigerated air thru the batteries..... love it.

or.... just build the battery box in the passenger seat in place of your girlfriend and keep cabin temp a nice steady 72 deg F to prevent compliants. )


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## ElectriCar (Jun 15, 2008)

Well I don't think it matters where you live, the specs are the specs. Better get some refrigerated air in there


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## dtbaker (Jan 5, 2008)

I guess there is a reason it was named 'Death Valley'.... you just plain don't want to go there in the summer whether you are driving a team of 1800's oxen or 2000's LI batteries.


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## JRP3 (Mar 7, 2008)

tomofreno said:


> Yeah, like this:
> http://www.diyelectriccar.com/forums/showpost.php?p=229687&postcount=77


I wonder about all the air space around that setup, probably better to be right on the bolt head if possible, though might not matter that much.


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## GizmoEV (Nov 28, 2009)

I thought I'd report my battery temperatures after my nearly 100 miles of driving my Gizmo yesterday. The ambient temperature was about 13°C at the end of the day, forgot to check at the start but the battery temperature was 11.8°C when I started. I drove ~44 miles in about 1.25 hours time using 111.9Ah and then started charging. I put 62.5Ah into the pack. The pack had stabilized at 21.0°C. I took a 6.6 mile drive using 17.2Ah and started charging again, putting 47.2Ah into the pack. The pack stabilized at 21.3°C. I took the same 6.6 mile run using 17.5Ah and then charged again, putting 12.9Ah into the pack. The pack temp stabilized at 21.7°C. I then headed back home and used 102.3Ah. About 30 miles of the trip was at WOT doing 50-55mph with a current draw of ~130A on this 200Ah pack. The pack temp stabilized at 26.0°C and was very close to that when I got home. My thermometer probe measures case temperature so there is always a lag in the temperature reading.

Total time in motion: 2h42m43s
Total Ah delivered by batteries: 252.22
Total Wh delivered by batteries: 15,878
Nominal voltage calculation: 15,127Wh/252.22Ah = 62.95V
Net Ah consumed: 248.82Ah
Regen Ah: 3.40
Total recharge kWh: 18.70
Total distance traveled: 98.3 miles
Deepest discharge: 126.2Ah

I have 3/4 inch pink solid foam insulation around most of the pack but there is a small amount of air exchange still. Each row of 10 cells has a 3/4" piece of aluminum bar stock sitting on a lower rib to hold the cells in place. Check my blog for pictures. There are 40 TS-LFP100AHA cells in a 2p20s arrangement.

Things to note: The temperature rise on the first leg of the trip was 9.2 Celsius degrees where as on the last leg of the trip the rise was only 4.2C°. The last leg was about 15 minutes shorter in time but was at higher sustained current draws. The first leg had some hill climbing to about 600 feet higher than the return trip.

It appears that as the temperature increases that the rate of increase diminishes. This would make sense in that the internal resistance of the batteries gets lower with higher temperature and that the rate of heat dissipation increases with greater temperature differences. Looking through my notebook I see I have another long run with a mid-temperature reading. Total discharge was 146.4Ah. Start temp: 6.5°C, mid-trip temp: 12.8°C (with out rest period so this is likely low), ending temp: 18.0°C so 6.3C° first leg and 5.2C° second leg.

Hopefully this will be useful to someone.


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## dtbaker (Jan 5, 2008)

GizmoEV said:


> About 30 miles of the trip was at WOT doing 50-55mph with a current draw of ~130A on this 200Ah pack. The pack temp stabilized at 26.0°C and was very close to that when I got home. My thermometer probe measures case temperature mid-trip temp: 12.8°C (with out rest period so this is likely low), ending temp: 18.0°C so 6.3C° first leg and 5.2C° second leg.


great info... especially considering you have a closed battery box with no ventilation. The moderate <1C draw looks like it doesn't generate much heat at all.... as expected.


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## ElectriCar (Jun 15, 2008)

OK Gizmo, I've browsed your build blog and ev album but didn't see anything about temp measurement system. So how are you doing that? I have a few extra wires in the cable from the hood to the pack available for something if needed. 

It's also encouraging to learn of your operating current and temp rise. My amps should be about the same or less possibly. I'm hoping to start burning electrons soon but I've ran into some snags. I have an idea now for the display mounting. Also found you can dim or shut off the CA back lighting. Did you know you could do that? 

Also a couple of questions:
1. Do you think I should install the second button on the CA? It came with only one button wired. 

2. Should I mount the shunt so it can count charging ah? I've already in stalled it after the contactor so I may need to move it for reading the charge.


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## dtbaker (Jan 5, 2008)

ElectriCar said:


> ...didn't see anything about temp measurement system. So how are you doing that?


I bought el cheapo remote temp thermometer that come with 2 remote probes, and I plan to just throw the receiver in the glovebox until I get the data I want...




ElectriCar said:


> 2. Should I mount the shunt so it can count charging ah? I've already in stalled it after the contactor so I may need to move it for reading the charge.


I would suggest yes mostly so you can feel confident of the total remaining those times you get a partial charge somewhere, or are turning system on/off multiple times during the day on errands. I would recommend having the CA 'always on'.... annd hitting the reset button manually if and when it drifts off zero after a full charge.


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## GizmoEV (Nov 28, 2009)

ElectriCar said:


> OK Gizmo, I've browsed your build blog and ev album but didn't see anything about temp measurement system. So how are you doing that? I have a few extra wires in the cable from the hood to the pack available for something if needed.


I referred to the blog so you could see how I mounted the batteries and the space between the rows. For temp sensing I'm using one of those indoor/outdoor thermometers with a wired probe. I placed the sensor between a row of batteries and use a piece of closed cell foam to hold it against the case of the batteries in the center of the pack. The foam also insulates the probe from ambient air temperature.



> It's also encouraging to learn of your operating current and temp rise. My amps should be about the same or less possibly. I'm hoping to start burning electrons soon but I've ran into some snags. I have an idea now for the display mounting. Also found you can dim or shut off the CA back lighting. Did you know you could do that?


Yes, I have the display off normally and it comes on when I flip on my headlight. I also installed a resistor so when they are on it isn't as bright so I'm not blinded at night. 



> 1. Do you think I should install the second button on the CA? It came with only one button wired.


I definitely would. I'd even throw away the original button because it isn't reliable. Jason at Grin Tech said that it was only there to get someone started. The second button allows you to get into setup without having to turn the unit off then back on.



> 2. Should I mount the shunt so it can count charging ah? I've already in stalled it after the contactor so I may need to move it for reading the charge.


Definitely! That is how I knew how much energy I had put back into my pack on my multiple partial charges. I have a 200Ah pack and I want to use no more than 160Ah. When it took me 112Ah to make the long leg of my trip I knew I had to charge until the CA read 45Ah or less.

dtbaker suggests that you leave the CA always on. I found that the Ah would count up much faster than the parasitic loads on my system warranted. Recharging always left the pack "not full" according to the CA. The problem is that with a 500A 50mV shunt the resolution of the CA is too big to accurately measure anything less than 0.1A which is around 65W with my pack. It didn't matter how many times I zeroed the CA it never would show zero consumption with everything powered off. I hooked up a relay which comes on with the key to power up the CA. In parallel with this relay I wire through the relays in the Zivan charger so that when the charger is plugged in the CA is on and then when the charger terminates then the CA turns off. I have another relay which turns off (shorts) the LEDs with the key on unless the headlight switch is turned on. It has all been working quite well.


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## dtbaker (Jan 5, 2008)

GizmoEV said:


> Recharging always left the pack "not full" according to the CA. The problem is that with a 500A 50mV shunt the resolution of the CA is too big to accurately measure anything less than 0.1A which is around 65W with my pack.


I am having trouble zeroing too... but they tell me it is the 'r9 resistor' needs to be changed to handle my 120v nominal (139v max post-charge) pack. Consequence is that the thing 'saturates' whatever that is, and voltage is not accurate, along with showing about -.3amp all the time when it should be zero..... they are sending a resistor and instructions, so I hope to fix that soon....


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## GizmoEV (Nov 28, 2009)

I'm running a max 70V setup. I would hope that the CA isn't "saturated" or something. The website lists upto 200V so I don't know why you need the resistor but maybe your unit is one of the early ones. I did have to calibrate the voltage readout in the setup menu. I don't remember what item it was but it wasn't hard. I think it was something about a multiplier. The CA read slightly high compared to my DMM.


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## ElectriCar (Jun 15, 2008)

After reading of the Nissan Leaf mileage issues, I thought about my potential winter trips. Since mileage is reduced when the batteries are cold, it occured to me that I may make a long trip out of town where I can't plug in. The truck may sit for a few hours in freezing temps with no battery heat. 

Then I thought about possibly adding a switch to allow the pack to power the heater since it's such a low watt heater. In an insulated box hopefully it won't get cold enough to warrant that but it just may. 

I think I should invest in some sort of temperature display/control, maybe parallel it with the "on" thermostat. I've been talking to a vendor about a controller that will operate on the car battery. I'll post more as I learn. That way it will be able to control the heater with the 240AC or the pack.


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## dtbaker (Jan 5, 2008)

you might wanna look at the product from heatline.com
it will run on DC or AC, and doesn't need a thermostat even.... you could just have an Anderson or circuit breaker to flip to run off traction pack if you are parked out in the cold.

my understanding is that it puts out variable wattage based on temp, but has no 'off'. It comes in different max output, and I guess you could put more or less in the bottom of the box according to how much you want. I got some that outputs between 1-8 watts per foot... but have not installed yet as we are fast approaching spring and I don't have time to mess with it right now.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> After reading of the Nissan Leaf mileage issues, I thought about my potential winter trips. Since mileage is reduced when the batteries are cold, it occured to me that I may make a long trip out of town where I can't plug in. The truck may sit for a few hours in freezing temps with no battery heat.
> 
> Then I thought about possibly adding a switch to allow the pack to power the heater since it's such a low watt heater. In an insulated box hopefully it won't get cold enough to warrant that but it just may.
> 
> I think I should invest in some sort of temperature display/control, maybe parallel it with the "on" thermostat. I've been talking to a vendor about a controller that will operate on the car battery. I'll post more as I learn. That way it will be able to control the heater with the 240AC or the pack.


I have info for u. U don't need anything to control from pack power. I have info about temp and voltage monitoring. Will post later from home.


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## ElectriCar (Jun 15, 2008)

dtbaker said:


> you might wanna look at the product from heatline.com
> it will run on DC or AC, and doesn't need a thermostat even.... you could just have an Anderson or circuit breaker to flip to run off traction pack if you are parked out in the cold.
> 
> my understanding is that it puts out variable wattage based on temp, but has no 'off'. It comes in different max output, and I guess you could put more or less in the bottom of the box according to how much you want. I got some that outputs between 1-8 watts per foot... but have not installed yet as we are fast approaching spring and I don't have time to mess with it right now.


It's the control voltage that has to be workable whether plugged in the wall or running off the pack. So to run off the 12V battery would be ideal.

I'm using the 17" flexwatt element DIYGuy turned me on to. It's about 85-110W depending on voltage. At pack voltage it would only output about 55 watts. Oh BTW, a purly resistive device which is all heating elements AFAIK will work on DC or AC. And they can operate at a lower than rated voltage however the wattage drops precipitously as the voltage drops a little bit. 

A quick formula to calculate wattage if you know the voltage is Voltage (E) squared / ohms = Watts (P). I have two different AC voltages I charge with thus this formula is very handy. Works with AC and DC as the AC voltage is actually the equivalent work capacity of DC voltage (RMS volts), IE 120V AC can do the same work as 120V DC.


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## dtbaker (Jan 5, 2008)

ElectriCar said:


> It's the control voltage that has to be workable whether plugged in the wall or running off the pack.


thats the cool thing about this heatline stuff... it is rated at either 120v or 240v, no 12v control required at all, just straight off the pack voltage any length you want to get the appropriate density of watts where you want them. Overlaps ok, and pretty tough stuff like Romex wire, only better.


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## DIYguy (Sep 18, 2008)

JRP3 said:


> I wonder about all the air space around that setup, probably better to be right on the bolt head if possible, though might not matter that much.


Hey JRP, yes, I kinda wanted to do that but have a height issue. . . so, I came up with the little tab. I've changed it a bit to keep it the same height as top of terminal bolt. I think that for temp sensing mode (summer), there won't be any air movement to decrease the source heat coming off the terminal...with the battery box lids on. So, maybe not too much of an issue... ???


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> It's the control voltage that has to be workable whether plugged in the wall or running off the pack. So to run off the 12V battery would be ideal.
> 
> I'm using the 17" flexwatt element DIYGuy turned me on to. It's about 85-110W depending on voltage. At pack voltage it would only output about 55 watts. Oh BTW, a purly resistive device which is all heating elements AFAIK will work on DC or AC. And they can operate at a lower than rated voltage however the wattage drops precipitously as the voltage drops a little bit.
> 
> A quick formula to calculate wattage if you know the voltage is Voltage (E) squared / ohms = Watts (P). I have two different AC voltages I charge with thus this formula is very handy. Works with AC and DC as the AC voltage is actually the equivalent work capacity of DC voltage (RMS volts), IE 120V AC can do the same work as 120V DC.


Ya, ok I was going to talk about the resistive tape taking either AC or DC, but obviously you know. I went round and round in the beginning with wall power vs pack power vs both to power the heaters. (for the same reasons you state). I eventually came back to the fact that using pack power really is gonna take care of all your needs. (or at least mine). If I am at home it doesn't matter too much as I am parked in a garage, but if it was outside, I can still flip the heaters on with pack power, and if I must run the charger, to keep it topped up, it's no biggy either. When away from home, it's got u covered also. The only time I could see it being an issue is if you park outside and are not charging for some reason and want to warm the pack over a long time frame (and have wall power available). Basically, if you have wall power, you can just plug in to charge, the heating is still viable with pack power, sure there are a few losses but.... 
Anyways, that's what I went with. 
As for temp monitoring, there are lots of cheapy indoor/outdoor wired or wireless units. I've been looking for wireless voltage monitors (side note) and temperature is usually included (pretty much the same thing). I keep running into either high price factory stuff or low end out of production or made for lipoly issues. Next best would be communication wire only (LAN) set up.
I ordered one of these to test. (remember that I wanted to use a sample # of batteries for redundant control of charger?) http://cgi.ebay.com/Voltage-Monitor...115?pt=LH_DefaultDomain_0&hash=item1e628656e3 . Each channel is 30 volts so each could do 7 cells, so 28 cells per board. So, depending on your pack number vs location, 2 or 3 of these boards could be used to monitor with hi/low signal out. I may buy a few of them if I like it. You just use a web browser to set up (like the Soliton).

This is the temp and voltage monitor (no relays tho) http://cgi.ebay.com/Temperature-and...902?pt=LH_DefaultDomain_0&hash=item20b071034e

Been toying with the idea of a notebook or small screen PC in there anyways. I dunno yet.


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## tomofreno (Mar 3, 2009)

> I think that for temp sensing mode (summer), there won't be any air movement to decrease the source heat coming off the terminal...with the battery box lids on. So, maybe not too much of an issue... ???


 Conduction to the metal it is fastened to should be much greater than radiation and convection to surrounding, fairly stagnant, air.


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## DIYguy (Sep 18, 2008)

tomofreno said:


> Conduction to the metal it is fastened to should be much greater than radiation and convection to surrounding, fairly stagnant, air.


Ya, that's what I figured also...


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> It's the control voltage that has to be workable whether plugged in the wall or running off the pack. So to run off the 12V battery would be ideal.


I just re-read this, and u got me wondering what you mean now. Control voltage? Should be straight fwd with 12 volts. Load voltage being AC vs DC is a bigger issue...at least for SSR. Usually they are one or the other. yes/no?


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## ElectriCar (Jun 15, 2008)

dtbaker said:


> thats the cool thing about this heatline stuff... it is rated at either 120v or 240v, no 12v control required at all, just straight off the pack voltage any length you want to get the appropriate density of watts where you want them. Overlaps ok, and pretty tough stuff like Romex wire, only better.


Well I was thinking of automatic control. That way I couldn't accidentally connect the charger to the truck while operating the heaters off the pack. If I did it could short the AC to the DC. I don't think that would be good, thus the desire to eliminate that possibility...


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## ElectriCar (Jun 15, 2008)

DIYguy said:


> Ya, ok I was going to talk about the resistive tape taking either AC or DC, but obviously you know. I went round and round in the beginning with wall power vs pack power vs both to power the heaters. (for the same reasons you state). I eventually came back to the fact that using pack power really is gonna take care of all your needs. (or at least mine). If I am at home it doesn't matter too much as I am parked in a garage, but if it was outside, I can still flip the heaters on with pack power, and if I must run the charger, to keep it topped up, it's no biggy either. When away from home, it's got u covered also. The only time I could see it being an issue is if you park outside and are not charging for some reason and want to warm the pack over a long time frame (and have wall power available). Basically, if you have wall power, you can just plug in to charge, the heating is still viable with pack power, sure there are a few losses but....
> Anyways, that's what I went with.
> As for temp monitoring, there are lots of cheapy indoor/outdoor wired or wireless units. I've been looking for wireless voltage monitors (side note) and temperature is usually included (pretty much the same thing). I keep running into either high price factory stuff or low end out of production or made for lipoly issues. Next best would be communication wire only (LAN) set up.
> I ordered one of these to test. (remember that I wanted to use a sample # of batteries for redundant control of charger?) http://cgi.ebay.com/Voltage-Monitor...115?pt=LH_DefaultDomain_0&hash=item1e628656e3 . Each channel is 30 volts so each could do 7 cells, so 28 cells per board. So, depending on your pack number vs location, 2 or 3 of these boards could be used to monitor with hi/low signal out. I may buy a few of them if I like it. You just use a web browser to set up (like the Soliton).
> ...


Dude you and I think alike so much. I was just last night telling the wife I've run out of dash for instruments. It would be so nice to have a 5x7 or so touch screen display with all this stuff integrated into it. I want a pre-charge volt meter, pack voltage meter, battery balance volt meter vs an LED unit (incidentally it came in the mail today), several switches, temp monitoring, temp control, amp meter, etc etc. I'm sure I'll find more things to monitor or control as time goes on. Lithium batteries are great but damn at the care and feeding requirements!


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## ElectriCar (Jun 15, 2008)

DIYguy said:


> I just re-read this, and u got me wondering what you mean now. Control voltage? Should be straight fwd with 12 volts. Load voltage being AC vs DC is a bigger issue...at least for SSR. Usually they are one or the other. yes/no?


Yes it would be. However if I ran mine on pack voltage only I wouldn't get very much heat from it as you can see from my earlier posts. That's why I'd like to have it on AC while connected to the charger. 

And here's a safety issue. It's common in reversing motor applications to use electrical AND mechanical interlocking to prevent power being applied for one rotation while the motor is being powered in the opposite direction. You wouldn't want DC on the heaters when you plug the charger in and have the AC circuit kick in. Then you'd have a mess! 

It's only a minor thing to wire it up with electrical interlocks and it could be done with mechanical interlocks as well. Now however you're adding more weight and complexity. The thing is, is it needed? You'll likely have more need for it though than me in South Carolina.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> Yes it would be. However if I ran mine on pack voltage only I wouldn't get very much heat from it as you can see from my earlier posts. That's why I'd like to have it on AC while connected to the charger.


Yes I recall you saying you weren't getting much heat...but didn't you also say you wired your heating elements in series? If you wire them in parallel you will get a lot more heat. Mine gets quite hot just on 120 volts. I suspect it will be way more than adequate on pack power.


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## ElectriCar (Jun 15, 2008)

They are rated only 120V so in series on 240V they will have the correct voltage on them. This is however at home when they will be in the garage. At work the voltage will be 208 so will only have 104 on each heater. There I go from 110W to 85 total watts. On the pack I'm only getting 25W per heater, 50w total. The ohms total connected to the load is 526 I believe. All this is from memory so it may be off a few watts but it's close.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> They are rated only 120V so in series on 240V they will have the correct voltage on them. This is however at home when they will be in the garage. At work the voltage will be 208 so will only have 104 on each heater. There I go from 110W to 85 total watts. On the pack I'm only getting 25W per heater, 50w total. The ohms total connected to the load is 526 I believe. All this is from memory so it may be off a few watts but it's close.


I see. So, your main reason to want to use AC, is to get the voltage level that will give you enough heat? Are you convinced that you can't use higher voltage on this tape? My tape will work on 240v and above that even (even though it's nominal rating is 120, it has "120V" as part of the model#). Maybe you should get the higher voltage model...or maybe test it? Again, I will reiterate, it is important to have two thermal switches in the control loop, one of them being mounted very close to the tape to prevent "local overheating" when on for long periods of time, even though ambient inside box is not high enough to turn off source.
Did u get a chance to look at my little voltage monitor? If so, what do you think? Perhaps I should post it where folks are looking at charger control or BMS alternatives. . . it's probably time for some more stone throwing anyways, been kinda quiet lately....lmao. Its not temp compensated, but otherwise is a really cheap way to get some redundant and peace of mind monitoring. No spaghetti wiring and u can even monitor your whole pack for 150 bucks or so...albeit in groups of 7 or 8.


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## CaptainZero (Apr 12, 2011)

What about drawing heated air from inside the car into the battery box with small ventilation going to outside the battery box?


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## DIYguy (Sep 18, 2008)

CaptainZero said:


> What about drawing heated air from inside the car into the battery box with small ventilation going to outside the battery box?


Hey Captain...ya, it's a thought I considered...but not for long. It's a fair bit of work when you have multiple boxes...and you have to generate enough heat one way or the other. The main issue though, there will be a lot of times (most probably) where you want to heat batts prior to heating the cabin. I envision a remote control even. I know you could do the same with cabin heat..and it may be even beneficial to warm up the cabin early, but I suspect the battery warming process to be much longer than the cabin warming, and I don't want to use any more energy than I have to. 

If you plan to move heat energy the most efficient way is through water/liquid. So, if I were to do a central heat source and distribute it, it would be with my fluid heater used for the cabin or similar with insulated tubing to each box and a radiator of some description in the bottom. 
I just find the heat tape to be so much simpler and "cleaner". 
I'm not saying that your idea wouldn't work though!


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## wherethere42 (Feb 28, 2011)

I havent read through the 16 pages of this post yet... I know lead acid batteries (not sure about other types) give off hydrogen gas especially when charging. Now the amount one battery puts out might not be much. But a large bank of batteries may produce a usable amount if one were able to capture it. Has anyone talked of or tried to build a box that could remove the hydrogen gas for use?


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## JRP3 (Mar 7, 2008)

Lithium doesn't produce hydrogen, and lead acid doesn't produce much.


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## ElectriCar (Jun 15, 2008)

DIYguy said:


> Did u get a chance to look at my little voltage monitor? If so, what do you think? Perhaps I should post it where folks are looking at charger control or BMS alternatives. . . it's probably time for some more stone throwing anyways, been kinda quiet lately....lmao. Its not temp compensated, but otherwise is a really cheap way to get some redundant and peace of mind monitoring. No spaghetti wiring and u can even monitor your whole pack for 150 bucks or so...albeit in groups of 7 or 8.


NO, where is it? My meter came in and I'm going to connect it today and start charging. That's the plan anyway.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> NO, where is it? My meter came in and I'm going to connect it today and start charging. That's the plan anyway.



Post #149... the one you quoted....lol lol


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## ElectriCar (Jun 15, 2008)

DIYguy said:


> Post #149... the one you quoted....lol lol


Oh yes I saw that. I thought you were talking about something you had already installed.


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## DIYguy (Sep 18, 2008)

Couple pics. Just have to install the Brad Harrison for bringing 12 volts and pack voltage in. I installed a terminal strip on top. I want to be able to easily check my cells without taking the boxes apart. 
Also, tried my hand at making a small braided connector. I need a few oddball length ones. It worked ok....fair bit of time consumed for one though..


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## ElectriCar (Jun 15, 2008)

Wow I was about to ask you where you found the straps. Box looks nice too. And I like terminal strips! They make a job look nice. I have one mounted on the firewall for ignition, ground connections etc. I'm however making my top so I can just remove it, taking the pack leads through the side and heater wiring through the sides.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> Wow I was about to ask you where you found the straps. Box looks nice too. And I like terminal strips! They make a job look nice. I have one mounted on the firewall for ignition, ground connections etc. I'm however making my top so I can just remove it, taking the pack leads through the side and heater wiring through the sides.


Thanks man. Ya, well since my cells are distributed in different boxes, It will be more of a pain than your one box to get at them all. That's why I'm trying this route.


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## DIYguy (Sep 18, 2008)

Couple more pics. Here u can see all my wires for terminal strips (so much for not wanting a lot of wires..lol ). The white thing is the heater SSR, and u can just see the top of the fan. The 2/0 cable runs down to the bulkhead Tweeco terminal. I labeled all the wires also. Oh, and u can see the temp switch for fan control also. There are a few more switches inside, I'll show you these next time cause I have to open the end up once more for the rest of the control wiring....


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## JRP3 (Mar 7, 2008)

DIYguy said:


> I bought three different switches. One is a 40C N/O switch for the fan. This is what you read about the temp in the booklet. At 40C it will close and allow 12v to the fan. This is DIGIKEY P/N 317-1505-ND.


Maybe I missed it but are you powering the fan directly with this, or using this to switch a relay? What's the power draw of the fan?


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## DIYguy (Sep 18, 2008)

JRP3 said:


> Maybe I missed it but are you powering the fan directly with this, or using this to switch a relay? What's the power draw of the fan?


The 12 v goes straight from the switch to the fan. No relay required. I don't recall what the current drae is, but its very low. 
The SSR I am using is for the battery pack power to the heaters. 12v control side with 2 switches and 220 V power side rated 10 amps.


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## tomofreno (Mar 3, 2009)

If you should develop a high resistance at that upper leftmost battery cable, it could get hot and melt the insulation on some of those wires under it. Probably won't happen, but might. "Double melt" (melts on the inside to seal to the cable - I think that is what it is called anyway) heat shrink on that cable would seal the crimp from dust and oxidation. Like this:

http://store.kta-ev.com/magna5663-051r.aspx

I'll quit pickin' now. Looks nice and secure.


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## DIYguy (Sep 18, 2008)

tomofreno said:


> If you should develop a high resistance at that upper leftmost battery cable, it could get hot and melt the insulation on some of those wires under it. Probably won't happen, but might. "Double melt" (melts on the inside to seal to the cable - I think that is what it is called anyway) heat shrink on that cable would seal the crimp from dust and oxidation. Like this:
> 
> http://store.kta-ev.com/magna5663-051r.aspx
> 
> I'll quit pickin' now. Looks nice and secure.


Thanks Tom, lol. I sure don't want the "double melt!! I'll give it a good seal to keep that nasty dust out. The other end of that cable isn't even connected yet. Lol.
Then again, what if the the connection on the upper right gets hot? Or the bottom left one? Hehehe.oh man, now u got me nervous. .


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## JRP3 (Mar 7, 2008)

DIYguy said:


> Thanks Tom, lol. I sure don't want the "double melt!!


Why not? He was referring to the heat shrink tubing with goo inside that seals connections.


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## DIYguy (Sep 18, 2008)

JRP3 said:


> Why not? He was referring to the heat shrink tubing with goo inside that seals connections.[/QUOTE
> ]
> Oh ya, I know the stuff u mean now. I was just havin fun with him.


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## ElectriCar (Jun 15, 2008)

DIYguy said:


> The 12 v goes straight from the switch to the fan. No relay required. I don't recall what the current drae is, but its very low.
> The SSR I am using is for the battery pack power to the heaters. 12v control side with 2 switches and 220 V power side rated 10 amps.


So you are going to use AC and the pack to power the heaters? And why did you use the SSR? Our thermostats are rated at 10A but not sure if they're DC rated, is that it?


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> So you are going to use AC and the pack to power the heaters?


Actually no. I thought about it a lot...and in the beginning I thought I would want this... but the more I thought I about it, the less I saw the need for it. Pack power is always there and if you are at home, u still power it... albeit indirectly.



ElectriCar said:


> And why did you use the SSR? Our thermostats are rated at 10A but not sure if they're DC rated, is that it?


yes, that's it. If you recall some folks tried this with the fluid heaters and the snap switches wouldn't take the high DC. So, I did my fluid heater this way and it has worked like a champ. Also, with 12 volt control, u don't have to worry about bringing pack power into the cab. I would assume you would want a on/off or like myself, thinking of a 3 position Summer/Winter/Off switch. (cooling/heating/off). Also, you can do things like a remote control to start the battery warmers prior to driving. I think with insulated boxes, u won't need the heaters on long once u start driving, unless u live where I do and it's -30C some mornings.  Remote temp readings should help me keep an eye on it, at least until I see their "personality".


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## bruceme (Dec 10, 2008)

A cheap and easy to heater that manages itself... Look into "Soil Heaters". These are low watt 120vac heater wire used to keep winter cole-beds (mini green houses) from freeezing over. They have a built in 70F thermostate and just plug in. Best part, they cost ~$30. I haven't tried hooking them to my DC system, but I'd imagine they can handle it.

http://www.google.com/search?q=economy soil heating cable&tbm=shop

I RTV glued my cable to a sheet of aluminum to dissipate the heat in my foam insulated box. So far so good!

-Bruce


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## DIYguy (Sep 18, 2008)

bruceme said:


> A cheap and easy to heater that manages itself... Look into "Soil Heaters". These are low watt 120vac heater wire used to keep winter cole-beds (mini green houses) from freeezing over. They have a built in 70F thermostate and just plug in. Best part, they cost ~$30. I haven't tried hooking them to my DC system, but I'd imagine they can handle it.
> 
> http://www.google.com/search?q=economy soil heating cable&tbm=shop
> 
> ...


Thanks Bruce. Yes, I did look at these and thought about using them however, I have very little space in some of my boxes and wanted a product that was as thin as possible. I think the soil cables will work fine on DC or AC also. It seems like a good solution. I did read of one fellow who had troubles with them..but can't remember why...??


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## JRP3 (Mar 7, 2008)

Don't know how many watts they are but I'd bet the built in thermostat won't handle DC switching very well.


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## ElectriCar (Jun 15, 2008)

I suspect it will handle the DC since it's such low current. Mine will be only 53W at packV which would draw only 0.30A, only 300ma.


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## JRP3 (Mar 7, 2008)

Then I wonder what 53 watts is going to do for a cold pack of cells? Doesn't seem like enough to warm up a cold pack.


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## ElectriCar (Jun 15, 2008)

Well you have to realize, it's in an insulated box lined with radiant barrier, it sleeps in the garage at home and it doesn't get extremely cold here, maybe 5-10F is the extreme lows here. But I'm using it on 240V and 208V which makes it about 85-100W. I just posted the output on 170V of the pack as a what if.


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## DIYguy (Sep 18, 2008)

JRP3 said:


> Don't know how many watts they are but I'd bet the built in thermostat won't handle DC switching very well.


Ya, you could be right. Maybe that's the problem I recall. One chap had his overheat and melt some insulation or something like that.


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## JRP3 (Mar 7, 2008)

It's a common problem that people have when using AC heaters with thermostats. They can't break the circuit with the DC load and the contacts weld closed and don't turn off.


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## DIYguy (Sep 18, 2008)

JRP3 said:


> It's a common problem that people have when using AC heaters with thermostats. They can't break the circuit with the DC load and the contacts weld closed and don't turn off.


Yes, ur absolutely right. With AC crossing zero, contacts break easier. It is well to check the particular switch though, because some are rated for DC use and also to check the voltage to know how high it is rated to.


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## ElectriCar (Jun 15, 2008)

I'm about to roll with my upgrade. Today I cut the holes in the top for the fans. I have to get some 120mm fan grills for them and then I can install them and close the box. 

I just have to get some sort of temperature measurement out of it. I'd like one with ambient temp and another readout for the box, like an indoor-outdoor unit. I don't recall this being discussed at length anywhere. Any ideas for that? I'm thinking a remote radio type transmitter signal will have a hard time leaving an enclosed aluminum box.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> I'm about to roll with my upgrade. Today I cut the holes in the top for the fans. I have to get some 120mm fan grills for them and then I can install them and close the box.
> 
> I just have to get some sort of temperature measurement out of it. I'd like one with ambient temp and another readout for the box, like an indoor-outdoor unit. I don't recall this being discussed at length anywhere. Any ideas for that? I'm thinking a remote radio type transmitter signal will have a hard time leaving an enclosed aluminum box.


Ya, u can buy the wireless ones for home use for 25 or 30 bucks. and u can get them that will accept 4 different transmitters... oh, I guess u just want two..  It should work. Made to go through walls of houses... besides, not expensive.


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## dtbaker (Jan 5, 2008)

the cheapo ones that I bought are wireless, but they also had probes on fairly long wires... easy to run the probe into the box, and tape it to something for conductive accuracy and have the sender unit closer to the receiver.


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## ElectriCar (Jun 15, 2008)

Thanks for the tip on the Taylor instruments! How long is the remote probe? My box is directly behind the cab. I think I could make a 6' cable work or possibly extend it. 

I also found a dual probe unit, model 1442 with two 6' lead probes for about $40. The body will operate down to -4F, so that is good. Sometimes my Paktrakr display would be almost invisible at less than 30F or so. It also has a 96hour temp recording feature and settable temp limits.


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## dtbaker (Jan 5, 2008)

I don't have it handy to stretch out, but I think its around 6' long....

and each receiver can rotate display thru 3 probes! ambient, motor, battery box, or whatever....


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## DIYguy (Sep 18, 2008)

So, I finished up the control (cooling, heating) wiring on the first box. I used a Brad Harrison bulkhead connector. There are 10 conductors... I have some spares there. 
The other boxes are all partially built up as well. All the cells are strapped now. I just have to finish up the control wiring and some details then put them in. Time has been a problem lately...


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## ElectriCar (Jun 15, 2008)

You need to buckle down and get moving man! I've got nearly 100 miles on mine in two days!


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> You need to buckle down and get moving man! I've got nearly 100 miles on mine in two days!


Ya... I know. I got the itch again. Doesn't help that I have 6 battery boxes. I put my power steering box in the other day, does that count?? lol


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## ElectriCar (Jun 15, 2008)

I'm collecting some very good data re wh/mile. It's better than I expected and about what I had hoped for. Man you'll love being able to drive the thing on multiple trips without recharging if necessary. 

And don't recall if you have the Zeva plus fuel gauge but man I love that thing! There's nothing comforting like looking at that familiar fuel gauge and know it's very close to your actual SOC. Also like the adjustable "low fuel" light capability. I connected it up to an LED in the dash by the switch for the tach input. It counts Ah also and will drive your tach if you switch the signal through a toggle switch like I did. It's nice to see an instant amp readout when you want versus waiting on the digital lag of the CS. It's 100A at 1000RPM.

Also have some data re my battery box fans I'll post when I get a photo to post.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> I'm collecting some very good data re wh/mile. It's better than I expected and about what I had hoped for. Man you'll love being able to drive the thing on multiple trips without recharging if necessary.
> 
> And don't recall if you have the Zeva plus fuel gauge but man I love that thing! There's nothing comforting like looking at that familiar fuel gauge and know it's very close to your actual SOC. Also like the adjustable "low fuel" light capability. I connected it up to an LED in the dash by the switch for the tach input. It counts Ah also and will drive your tach if you switch the signal through a toggle switch like I did. It's nice to see an instant amp readout when you want versus waiting on the digital lag of the CS. It's 100A at 1000RPM.
> 
> Also have some data re my battery box fans I'll post when I get a photo to post.


Nice to see the excitement.  Yes, I bought the zeva as well. Looking fwd to more info.


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## dtbaker (Jan 5, 2008)

do you have a link to the Zeva gauge? I'd like to compare features and cost to Dimitri's evDisplay .

some of the others that look ok functionally are just way too expensive.... 

The new Cycle Analyst looks ok and is pretty affordable, but my older one did not handle 120v without replacing a resistor inside, which I haven't had time for yet. The CA also does not have temp compensation, and uses shunt rather than Hall Effect... pros and cons there I guess.


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## DIYguy (Sep 18, 2008)

Hey Dan. here u go.

http://www.evworks.com.au/index.php?product=INS-ZEVA-FGDP


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## dtbaker (Jan 5, 2008)

DIYguy said:


> Hey Dan. here u go.
> 
> http://www.evworks.com.au/index.php?product=INS-ZEVA-FGDP



looks pretty good. I just read thru the manual... appears that the 'empty' reading basically requires driving around until you see the knee of the pack start a little voltage sag, and then turning the pot till it reads empty.

Perhaps not terrible to do that once, but makes me pretty nervous as I really don't want to EVER go that deep into discharge, not even once! From what I saw while balancing, once that cell voltage starts dropping, it drops like a rock. You'd have to be driving around with your eyes GLUED to the pack voltage and stop the second it started dropping.... then figure out how to charge enough to get home?!


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## JRP3 (Mar 7, 2008)

Actually if you're driving around at say 45+ mph and your voltage sags to "empty" you can still drive a couple miles at 20 mph. Ask me how I know  "Empty" under load isn't really empty. When doing that sort of test I just finish up by doing short drives around the block. If your pack is bottom balanced you won't drive any single cell to zero so you won't hurt anything.


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## ElectriCar (Jun 15, 2008)

dtbaker said:


> looks pretty good. I just read thru the manual... appears that the 'empty' reading basically requires driving around until you see the knee of the pack start a little voltage sag, and then turning the pot till it reads empty...


I don't think that's necessary but it would be the most accurate. With my CA running I know how much is left in the tank so I am comparing that to the gauge. Here's what I did yesterday. 

After charging I unplugged the pack to kill any parasitic current flow, important for the start up calibration of the current sensor on power up for the Zeva. I then adjusted one of the pots until the meter registered full as it did with gas. *IMPORTANT - If you kill power to the unit, it will not be correct again until you recharge and kill the power with the pack disconnected.*

Quickly after driving a bit the LED I installed for "low fuel" indicator came on. There's a pot to adjust it too so I backed off until the light went off. The manual says one turn of one of the pots represents approximately 20Ah. So I turned it 10 times to get my empty reference. Once I drove more the gauge I noticed was going the wrong way. To fix this I turned one of them until it went the other way, it's set up to drive a meter that way if you wish, the middle pot determines the direction of movement and is the Ah setting pot. 

I also had to adjust the "full" pot more to get enough movement. You'll just have to adjust it and play with it but you'll get it. *Some of the pots I noticed interplay with the others adjustment and their one page sheet doesn't get into the details on that.*

Right now I'm sitting on 3/4 tank and have used about 23Ah so it's close. I didn't charge it last night and am planning to drive it a bit further today without recharging to make sure it's accurate.


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## ElectriCar (Jun 15, 2008)

JRP3 said:


> Actually if you're driving around at say 45+ mph and your voltage sags to "empty" you can still drive a couple miles at 20 mph. Ask me how I know  "Empty" under load isn't really empty. When doing that sort of test I just finish up by doing short drives around the block. If your pack is bottom balanced you won't drive any single cell to zero so you won't hurt anything.


When this thing says empty, it's empty! *It is an AH counter, not based on voltage. * I'm setting mine up to be just like a gasser so when it's just below E you're walking! In that effort I installed a low fuel LED which will be set to come on at about 20%SOC or about 1/8 -1/4 tank indication I think.


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## JRP3 (Mar 7, 2008)

That's true, when I had my low SOC incident I was using voltage as a gauge. I have set my EV Display to show "0" before it's actually empty, just as most gas gauges show empty well before the car stops moving.


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## tomofreno (Mar 3, 2009)

I was driving home last night from a bit over 70 mile trip, roughly 40% at about 55 mph rest at 35 to 40 mph when the TBS guage backlight started flashing, and the screen started flashing "Lo", and said "Charge" in the lower left corner. Prior to that the last of 5 total display bars (each representing 20% of total charge) started flashing when half the charge that bar represents was consumed. I don't see how anyone could miss seeing they are running low on charge with this gauge. I have 35% SOC defined as empty. When it hits that SOC the screen flashes "Empty". I used 113Ah total on the trip, or just under 63% DoD, 37% left.


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## ElectriCar (Jun 15, 2008)

Tom why are leaving so much on the table? From what I've read, if all your cells are very close in ah and you balance them, top or bottom, you should be able to discharge much lower than 65% and very safely without concern for losing one. Ie if your cells vary from 217-219, you should be able to take them down to 200-205 easily, only leaving a small percentage for insurance. Even down to 190 wouldn't be leaving 35% out there. Or is there another reason for that?


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## dtbaker (Jan 5, 2008)

ElectriCar said:


> ...you should be able to discharge much lower than 65%


if Tom is anything like me... I want bells and whistles to start no lower than 70% DOD. I want plenty of cushion to allow for variation in accuracy due to temp and other factors as well. I am betting that less than 70% discharge for regular use will give me more life cycles, and I have top balanced so I don't want to go anywhere NEAR the bottom.


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## GizmoEV (Nov 28, 2009)

I concur with what Dan said above. Even though I don't think I'll wear out my pack in my Gizmo from cycle life before calendar life kills them off I don't want to chance it. I will push to 80%DOD if on occasion but it is rare.


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## dtbaker (Jan 5, 2008)

GizmoEV said:


> ... I don't think I'll wear out my pack in my Gizmo from cycle life before calendar life kills them off ...


from what I know LiFePO4 doesn't really have calender life (like lead or nimh) because the shuttle is mechanical, not chemical.


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## GizmoEV (Nov 28, 2009)

dtbaker said:


> from what I know LiFePO4 doesn't really have calender life (like lead or nimh) because the shuttle is mechanical, not chemical.


But the electrolyte starts breaking down immediately after manufacturing. The higher the temp the faster the breakdown. That is what I've understood from the literature I've read and from the CM professor's video.


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## dtbaker (Jan 5, 2008)

GizmoEV said:


> But the electrolyte starts breaking down immediately after manufacturing. The higher the temp the faster the breakdown. That is what I've understood from the literature I've read and from the CM professor's video.



hhhmmmm, I dunno, I thought it broke down mostly at higher temps, not under 'normal' conditions. Might be a good question to ask the expert! I'd be interested to know what it is that limits the life of the cells, and thus how to optimize cycles.


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## tomofreno (Mar 3, 2009)

> Tom why are leaving so much on the table?


 Pretty much what Dan said - lifetime, plus uncertainty of capacity over years of use, plus nice comfortable cushion. I typically don't need 65%. I recharge many times at 40 to 60% SOC. I have driven to 30% SOC several times. I know I can easily drive 10 more miles after the "Empty" warning with no worries, but I won't tell that to anyone else who drives it.


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## tomofreno (Mar 3, 2009)

> But the electrolyte starts breaking down immediately after manufacturing. The higher the temp the faster the breakdown. That is what I've understood from the literature I've read and from the CM professor's video.


 I didn't hear this in the video. I think the solvents are quite stable as long as high temperatures are avoided. The CMU prof said avoid temp's greater than 50 to 60 C at first, then later said 60. I've had mine to 46 C without noticeable effect, i.e. still getting about the same range as last summer when it occurred. Don't know of course about the effect on life cycles. Seems it is going to be about impossible to quantify this with so much variability in the way people operate.


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## GizmoEV (Nov 28, 2009)

tomofreno said:


> I didn't hear this in the video. I think the solvents are quite stable as long as high temperatures are avoided. The CMU prof said avoid temp's greater than 50 to 60 C at first, then later said 60. I've had mine to 46 C without noticeable effect, i.e. still getting about the same range as last summer when it occurred. Don't know of course about the effect on life cycles. Seems it is going to be about impossible to quantify this with so much variability in the way people operate.


I need to watch it again and try to dig up where else I got that the electrolyte broke down at most (all?) temperatures but like most chemical reactions it was faster the higher the temperature is. Like you said, the variability of use is so great it is nearly impossible to quantify things.

On the setting "empty" to 65-70%DOD it also gives an apparent longer pack life. What I mean is that if you regularly need 65 miles but build your pack for 100 mile range you still have "full" range when your pack can only deliver 65 miles thus you get a longer effective pack life. If, on the other hand, the pack is sized for 70 mile range it won't be long before it won't take you the 65 miles needed.


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## PeterH (Mar 20, 2009)

Wow, just spent over an hour reading this entire thread only to reach the end and not find out 'who dun it'!

It has been about 8 months since the last post to this thread... did the Flex Watt Heat Tape solution for battery warming work?

I'm right at the point where I need to do something about battery warming and I'm really hoping this solution worked so I don't have to start plumbing my boxes for circulating heated fluid to keep them all at the same charge-friendly temperature.

Thanks
Peter


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## DIYguy (Sep 18, 2008)

Hello Peter,



PeterH said:


> Wow, just spent over an hour reading this entire thread only to reach the end and not find out 'who dun it'!


 Does that mean your are thankful.... or perturbed? As u can see, I did it. I think Electriccar did it also.



PeterH said:


> has been about 8 months since the last post to this thread... did the Flex Watt Heat Tape solution for battery warming work?


 Ya, sorry about that. I should have put some finale to it. Yes, it works.



PeterH said:


> I'm right at the point where I need to do something about battery warming and I'm really hoping this solution worked so I don't have to start plumbing my boxes for circulating heated fluid to keep them all at the same charge-friendly temperature.
> 
> Thanks
> Peter


It's a personal thing and there are lots of ways to skin a cat. Personally, I couldn't come to terms with the fluid method in my application. It would have been a nightmare with all my boxes spread out. One big one like JR did is more reasonable. 

I park in the garage so, I'm not sure if I would have enough heating for a -30C night outside or not, haven't tried but depending where u live, u could put more of the flex watt in the box. The guy I talked to there, said they had done some battery box applications before and he indicated it was for Ford so perhaps it was the old Ranger EV program and I think they did the sides of the boxes as well. All depends on wattage I suppose. Butt, I think it's one of the most elegant solutions.


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## PeterH (Mar 20, 2009)

Thank you for your quick reply. I was hoping to learn more before this weekend. I was going to spend Saturday cutting up a big sheet of 1/8 inch aluminum to get started on an idea I've been working on for a fluid based heating system. 

But like you, my cells are scattered between 5 boxes and I haven't come up with a way to ensure all 5 were at nearly the same temperature.

I really like your approach to this problem. I'll have to go back through this thread to see the details of how you attached things.

I'm picturing a plate of aluminum under the batteries and the Flex Heat Tape below that, which puts the tape on top of 1 inch of pink foam insulation that presently insulates the bottom of the box. The sides are insulated with 1/2 in white foam insulation, only because I couldn't find 1/2 pink foam...

How are you controlling and measuring temperature in each box? I watched the videos from BigApplePets and learned about their thermostat and single sensor. But I'm thinking each box needs to be monitored and controlled...

Sorry, if you've already answered those questions earlier in this thread. I'll go back and skim the thread again to see what details I can learn.

Meanwhile, I'm happy to scrap my fluid heating plans and get started on this approach. I will be parking in an unheated garage where I can easily apply 110VAC to power the heaters. If needed later, I could easily add an inverter to power them while parked in very cold conditions, but only if it is really needed and grid power wasn't easily available. 

Thanks,
Peter


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## DIYguy (Sep 18, 2008)

I think most of the answers are in the thread. I would encourage you to really think about the power source for the heaters. In the beginning, I wanted it all. In the end I realized that powering from the battery made the most sense. . .at least to me. By powering from the battery, you have a self sufficient system able to maintain itself anywhere. Secondly, if you want to ensure it is fully charged, just keep the charger plugged in. You will be powering your heaters indirectly. It's not all that much energy anyways. 
worst case scenario.... Lets say you drive to work and can't plug in to charge or heat. As long as u don't worry about range, on the coldest days, u can still warm the batteries.
Having larger than needed battery and current capability does help to mask any reduction in performance also. I notice a big difference when asking for 1000 amps (voltage drop) if batteries are at zero C. . however, if only looking for a 400 amp acceleration, which is more than enough, u don't notice anything. 
The nice thing about the Flex Watt tape is that it will work with AC or DC however, your circuit design will obviously change.
I used DC SSR's with switching power routed through two thermal (snap) switches (of different trip points). I think this is an important point. You need one switch very close to the heat source and one further away for ambient. This protects the element from overheating while having one to control ambient. I learned this from some other applications. Elements can overheat in certain circumstances when on for extended periods if allowed to get too hot.

Also, make sure that the heat generated from the element at the actual power level it will run at, does not damage your choice of insulating materials. I did some testing to ensure this. white styrofoam for example can deform/melt at some fairly low temps. Just something to check.

Good luck.


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## PeterH (Mar 20, 2009)

Thanks again. I just ordered 20 feet of the 3 inch wide Flexwatt Heat Tape. My next task is to design a practical control system that will monitor the temp in each box and control the Flexwatt in each box.

Thinking about trying to use an Arduino board as the brains behind it all. I found a posting about a home brewer using an Arduino board and some sensors to monitor the temp for his keg of beer. Doesn't take much imagination to picture using the same technology to monitor my battery heating... at least not from the comfort of my desk chair... we will see how that works out when the electrons hit the conductor. 

I'll post an update here and maybe start another thread if I have enough success with the idea of using a computer to monitor and control the warming system.

Thanks for the advise on basic considerations. That is a good foundation for my next steps. 

Peter


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## swoozle (Nov 13, 2011)

PeterH said:


> Thanks again. I just ordered 20 feet of the 3 inch wide Flexwatt Heat Tape.


Peter, where did you order from and were you pleased with the purchase? I'm ready to get some Flexwatt as well.

Thx


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## PeterH (Mar 20, 2009)

Hi there,

I orded my Flexi-watt tape from http://www.beanfarm.com/

They sound like a small mom & pop operation but delivered the goods... and I think they had a good price. 

I only ordered the tape... non of the connectors or other accessories because as you can see in this thread: http://www.diyelectriccar.com/forum...tt-battery-heater-control-system-70146p2.html, you can easily trim back the insulation and solder right to the silver strip.

Pete


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## swoozle (Nov 13, 2011)

PeterH said:


> Hi there,
> 
> I orded my Flexi-watt tape from http://www.beanfarm.com/


Nice, they are 10 miles away from me


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## bruceme (Dec 10, 2008)

JRP3 said:


> Don't know how many watts they are but I'd bet the built in thermostat won't handle DC switching very well.


I directly tapped the battery with a small NEMA-5 female plug (w/5a fuse) and I do run it both on my 144vdc and plug it into the 120vac. When I run it on ac, it does just fine. On DC after a few hours it smells very slightly of hot plastic. So I try to only run on DC when I'm out and it's very cold (below 20).

-Bruce


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## ElectriCar (Jun 15, 2008)

Got mine from bean farm also. So Bruce, do you have an aluminum sheet or such for a heat spreader on top of it? My batteries sit on the sheet and I have that foam insulation underneath it but I heat it with 120V only.


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## bruceme (Dec 10, 2008)

I love this thread, it's critical to EV commuters (30+mi/day, every day, rain, snow, blistering heat) ... 

The battery box is the #1 most important component in a practical electric vehicle conversion. A properly designed/placed battery box _IS_ the difference between a poorly performing, short lived toy and a real all season vehicle. 

- Plan carefully
- Take your time, leave room
- Insulate, heat and ventilate!

-Bruce


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## bruceme (Dec 10, 2008)

ElectriCar said:


> Got mine from bean farm also. So Bruce, do you have an aluminum sheet or such for a heat spreader on top of it? My batteries sit on the sheet and I have that foam insulation underneath it but I heat it with 120V only.


Yes, I do... very simple, I laid it out in a big double-"U" (U in a U) pattern, I used about 6 small zip ties (drilled 1/8" whole in the aluminum) to hold it in place, then scuffed/RTV'd in in about a dozen places so it would have good adherence. I have pictures. I'll try to post.


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## bruceme (Dec 10, 2008)

Sry, I have pictures of the battery box being built, but not the soil heater


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## swoozle (Nov 13, 2011)

swoozle said:


> Nice, they are 10 miles away from me


 But they won't let me come pick up a prepaid order. 
"Not worth the gas to come out", they sez. $7 for shipping for it to go AWAY from me and then back, vs a buck or two to get it myself.
Oh well.


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## mharvey (Oct 30, 2009)

PeterH said:


> Hi there,
> 
> I orded my Flexi-watt tape from http://www.beanfarm.com/
> 
> ...


Just ordered from bean also. I'm interested in any feedback on thermal control. Has anyone tried the Herpstat Intro (horrible name)? http://beanfarm.com/product_info.php?products_id=6075 . At 99 bucks including the probe I figured I'd give it a shot since I'm only doing two 2ft strips of the 11". Has a nice digital readout, flush mounts, and will power two separate heat sources. 

Great thread btw. Thanks all for sharing your experiences.


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## PeterH (Mar 20, 2009)

If you have only one box then it is well worth a try. I have five boxes and tend to complicate things... So I have all the sensors in place and all of the wiring in place and will soon work on the arduino program to monitor and control the individual boxes.

But hard to really test it till the temps in my area head south for the winter.

Please let us know how it works for you!

Pete


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## mharvey (Oct 30, 2009)

PeterH said:


> If you have only one box then it is well worth a try. I have five boxes and tend to complicate things... So I have all the sensors in place and all of the wiring in place and will soon work on the arduino program to monitor and control the individual boxes.
> 
> But hard to really test it till the temps in my area head south for the winter.
> 
> ...


Yes, only a single box in place of the gas tank with fan cooling automated by thermal switch and the heating of course only during charging. I'll post pics as it develops.


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## dtbaker (Jan 5, 2008)

bruceme said:


> I directly tapped the battery with a small NEMA-5 female plug (w/5a fuse) and I do run it both on my 144vdc and plug it into the 120vac. When I run it on ac, it does just fine. On DC after a few hours it smells very slightly of hot plastic. So I try to only run on DC when I'm out and it's very cold (below 20).
> 
> -Bruce



really bad idea to run AC soil heating cable w/ DC. The AC switches WILL melt, and there are several reports of smouldering and even fires.... the thermostats don't work terribly well unless buried in DIRT to even out the temp fluctuations as intended.

I got some 'heattape' from canada with is variable resistance based on temp 1 to 8 watts per foot and no switches so it is fine on either DC or AC.


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## bruceme (Dec 10, 2008)

dtbaker said:


> really bad idea to run AC soil heating cable w/ DC. The AC switches WILL melt, and there are several reports of smouldering and even fires.... the thermostats don't work terribly well unless buried in DIRT to even out the temp fluctuations as intended.
> 
> I got some 'heattape' from canada with is variable resistance based on temp 1 to 8 watts per foot and no switches so it is fine on either DC or AC.


You're dead on. 90% of the time I run it AC (overnight heating while charging). When I'm out and it's -20F and I need it warmed up, I'll hit it with the 144vdc off the pack, it does smell when I get done with that, so I humbly agree. 

When next I pull the batteries out, I'll replace the thermal switch with a 70f AC/DC switch I purchased that's rated for this purpose.

-Bruce


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## bruceme (Dec 10, 2008)

PeterH said:


> If you have only one box then it is well worth a try. I have five boxes and tend to complicate things... So I have all the sensors in place and all of the wiring in place and will soon work on the arduino program to monitor and control the individual boxes.
> 
> But hard to really test it till the temps in my area head south for the winter.
> 
> ...


'Tis the gift to be simple' 

I wrote software for a living... Go to Makers fairs, love cool mc projects (interested in knowing more about yours). But when it comes to my EV, the systems that aren't there, never fail me. One battery box is hard enough to get right.


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## mharvey (Oct 30, 2009)

As promised, this job is complete. I did order the heat tape 11" from Beanfarm as well as their Herpstat thermostat. It all worked out nicely. Build pics are located at http://www.harveyev.com/gallery.html?galAlbum=6. Dont mind the site as I am still redoing it. I have not time to add all my builds for other projects. There are many shots of the battery box build including the biscuit fans with 140F thermistor to drive them under extreme heat situations. They never actually came on during my test runs @ 40 miles in the dead of summer, but they were cheap and a nice insurance policy.


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## jeremyjs (Sep 22, 2010)

Not sure if anyone's mentioned it yet, but it seems seedling heat mats should work exceptionally well. They come in tons of different sizes and are gentle enough not to cook seedlings, so no need for a heat spreader. Some of them were as big as 2 ft by 8 ft. to under a foot square and in a variety of wattage's.


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## DIYguy (Sep 18, 2008)

mharvey said:


> As promised, this job is complete. I did order the heat tape 11" from Beanfarm as well as their Herpstat thermostat. It all worked out nicely. Build pics are located at http://www.harveyev.com/gallery.html?galAlbum=6. Dont mind the site as I am still redoing it. I have not time to add all my builds for other projects. There are many shots of the battery box build including the biscuit fans with 140F thermistor to drive them under extreme heat situations. They never actually came on during my test runs @ 40 miles in the dead of summer, but they were cheap and a nice insurance policy.


Nice job. I like the wood mock ups, it really makes for a good fit and exposes those potential interference/fit problems.


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## JRP3 (Mar 7, 2008)

jeremyjs said:


> Not sure if anyone's mentioned it yet, but it seems seedling heat mats should work exceptionally well. They come in tons of different sizes and are gentle enough not to cook seedlings, so no need for a heat spreader. Some of them were as big as 2 ft by 8 ft. to under a foot square and in a variety of wattage's.


The quick look I had at them said they would "warm the root area" 10-20 degrees above ambient, which does not sound like enough to warm up a battery pack in sub freezing temps.


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## mharvey (Oct 30, 2009)

DIYguy said:


> Nice job. I like the wood mock ups, it really makes for a good fit and exposes those potential interference/fit problems.


Thanks. Luan and hot glue are a surprisingly strong mockup tool. I actually had the full pack in the wooden mockup and was turning the whole thing on the bench w/o the box torquing at all. And yes, when your paying a guy to fabricate the whole thing, it's nice to say "Make me this exactly." and know it will work


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## Caps18 (Jun 8, 2008)

This is the next step for me now I believe. I know I am going to use 45 LiFePO4 batteries (144V, 100Ah) under the bed of the S-10. 

Everything else I have to come up with a good design with the experience of other people have found to work well.

I am thinking about using a sheet of Aluminum, cut & bent, bolted to the frame, painted on the outside, with some insulation around the batteries. Some type of battery warmer (do the batteries just have to get to temp a few seconds before you start driving, or do they always need to be at room temp?), and a 12V industrial computer fan with some water proof vents.

I also would need a protective cover on top of the batteries, some way to keep anything from shorting them out, and a good way to balance the weight (~360 lbs).

Here is a good description of lead acid ones, I would like to find someone who has done LiFePO4 boxes and put something to deflect the air instead of a flat box.
http://waynesev.com/ev/battery_boxes.html

I am hoping to be done with this after the next two to three weekends.


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## dougingraham (Jul 26, 2011)

Caps18 said:


> This is the next step for me now I believe. I know I am going to use 45 LiFePO4 batteries (144V, 100Ah) under the bed of the S-10.
> 
> I am thinking about using a sheet of Aluminum, cut & bent, bolted to the frame, painted on the outside, with some insulation around the batteries. Some type of battery warmer (do the batteries just have to get to temp a few seconds before you start driving, or do they always need to be at room temp?), and a 12V industrial computer fan with some water proof vents.
> 
> I also would need a protective cover on top of the batteries, some way to keep anything from shorting them out, and a good way to balance the weight (~360 lbs).


The general consensus is you dont need to cool LiFePo4 cells as long as you aren't exceeding the ratings. With your 100Ah cells as long as you keep the average crusing current under the continuous C rating you should be ok. This would be 300 amps on a 3C battery (around 58 horsepower with your listed system). And I dont think a simple fan arrangement will cool them in the situation where you are exceeding the C rating for extended periods.

If the batteries are really cold your range and performance will be reduced so warming to something above freezing would be a good idea. And to charge they need to be above freezing or they won't accept a charge. A charger that has a typical charging cutoff will turn off almost immediately.

I dont know what you mean by "balance the weight."


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## dtbaker (Jan 5, 2008)

Caps18 said:


> I am thinking about using a sheet of Aluminum, cut & bent, bolted to the frame, painted on the outside,


aluminum is a good choice, being fairly stiff and certainly light. If you have a way to make long bends, and/or weld. no paint required, just leave it shiny and save some time and money.  HIGHLY recommend designing in thin plastic sheeting or foam around the edges and non-conductive lid liner.

I used steel railed edges and sealed polypro sheet boxes on my original boxes for lead-acid. worked great, but steel wouldn't be required for lighter Li. My front rack is just heat-welded polypro bolted down on a steel Ubeam with a polycarb lid for show.n.tell

My boxes are relatively 'tight' with no venting OR insulation OR heating at the moment since my vehicle is in a garage, and not left out for extended periods since I work from home. Pack temp is relatively stable in winter since gargage is pretty warm. I had thermometers in boxes, and did not see temps rise much over ambient during my usual daily driving.



Caps18 said:


> with some insulation around the batteries.


really depends on your location, whether vehicle is garaged at night in winter average daytime temps if vehicle is outside at work. Since Li doesn't off-gas, boxes can be 'tight'. Insulation around edges MAY make it problematic to get a nice tight fit for a little clamping.



Caps18 said:


> Some type of battery warmer (do the batteries just have to get to temp a few seconds before you start driving, or do they always need to be at room temp?),


they must be above freezing when charging. they will operate better with less sag if maintained 'warm'. take a look at 'farnum battery heating pads' or some products made to keep baby pigs happy, or product from heatline.com (variable resistance cable 1w-8w per foot on either AC or DC!)



Caps18 said:


> and a 12V industrial computer fan with some water proof vents.


unlikely you need cooling fans unless you are somewhere really hot, or run at high load for extended highway travel.



Caps18 said:


> I also would need a protective cover on top of the batteries, some way to keep anything from shorting them out,


yes... foam lined aluminum, or plastic sheeting. Lexan, polycarb, or polypro



Caps18 said:


> and a good way to balance the weight (~360 lbs).


I used a gang of cheap batchroom scales (3) and took measurements at front and rear wheels to jigger things around a little.



Caps18 said:


> something to deflect the air instead of a flat box.


aero considerations are not huge at low speeds, but a full belly-pan wont hurt.  pan under motor would be highly recommended just to reduce debris and splash.


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## Caps18 (Jun 8, 2008)

That is good info to know. I guess I won't need to worry about the heat until I move back to the SouthWest. I'm not going to be driving on the highway for long distances at this time either.

I am also going to use liquid-tight PVC conduit painted orange since the orange color one costs 10 times as much (and I don't need it to flex). I will probably run the positive and negative cable in separate runs.

http://www.mcmaster.com/#liquid-tight-flexible-nonmetallic-conduit/=j5rn9o


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## dtbaker (Jan 5, 2008)

Caps18 said:


> I am also going to use liquid-tight PVC conduit painted orange since the orange color one costs 10 times as much (and I don't need it to flex). I will probably run the positive and negative cable in separate runs.
> 
> http://www.mcmaster.com/#liquid-tight-flexible-nonmetallic-conduit/=j5rn9o



I tried messing with liquid-tight metal lined flex conduit, and it is a BITCH to work with and very expensive. gave up and ran my main cables from front to back in regular rigid gray PVC hung in the exhaust tunnel. Paint it orange if it makes you happy. 

I'd suggest running the cables together as it will cut down on the EMF, which will otherwise kill all radio reception and maybe interfere with nearby electronic devices. you don't want to pack the conduit tight, but two 2/0 cables will pull down PVC pretty easily.


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## Caps18 (Jun 8, 2008)

I'm a big fan of liquid-tight. I have never had a problem working with it before, and I know that it will last a long time.

I won't have a radio in this truck. I will be using an iPhone and an amplifier.  But, I will run the cables one on top of the other.


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## dtbaker (Jan 5, 2008)

Caps18 said:


> I'm a big fan of liquid-tight. I have never had a problem working with it before, and I know that it will last a long time.


we might be talking about different stuff.... I tried to use some of the flexible spiral metal with the plastic outer coating.... like for hot tubs and roof appliances. super tough, but I found it very hard to work with in a diameter larger enough for 2 x 2/0 cables, and WAY heavier and more expensive that plain old rigid PVC. My exhaust tunnel from engine bay to rear battery location was a straight run, and there were a few handy exhaust hanger locations I was able to use for pipe hangers.


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## Caps18 (Jun 8, 2008)

That looks good, and I have used the hard PVC in other projects before, but your measurements have to be right on and there are quite a few bends. Can I ask how you attached it to the box? I have used a female coupler, but finding the locking ring for the inside was tough if I remember right.

Yes, there is metallic liquid-tight that is tough to cut with the metal wound around the inside. It is hard to cut and has sharp pieces, but once it is done, it is great. I was thinking of using the non-metallic version, which is more flexible and easier to cut with a hacksaw.


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## dtbaker (Jan 5, 2008)

Caps18 said:


> Can I ask how you attached it to the box? I have used a female coupler, but finding the locking ring for the inside was tough if I remember right.


I used a PVC female coupler and lock ring from electrical conduit coupler. see pic. Also, I used vacuum and 'mouse' to pull construction string thru, then pulled cables. I didn't want to buy fish tape for one use.....


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## ricklearned (Mar 3, 2012)

Carlon make a product that you can buy at Home Depot or Lowes. I sprayed it orange because it nominally comes in blue. I also used some of it for low voltage that I sprayed black.

For bigger cables I used Kwikpath resi raceway. I have a 4 ft run to the front of my VW from the heater channel and another 3 ft run from the back seat area, over the axle to the engine compartment. I used 1.5 inch because I had 
#10 charger cables and 2/0 cables in that tube. The next smaller size would probably work for #2/0 cable alone. I found it in orange at this place:

http://www.hometech.com/hts/products/wiring/raceways/ip-kphc.html


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## dtbaker (Jan 5, 2008)

ricklearned said:


> I used 1.5 inch because I had
> #10 charger cables and 2/0 cables in that tube. The next smaller size would probably work for #2/0 cable alone. I found it in orange at this place:
> 
> http://www.hometech.com/hts/products/wiring/raceways/ip-kphc.html


great find.... my local home depot and lowes do not carry this stuff, so might have to mail order...


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## tomofreno (Mar 3, 2009)

DIYguy said:


> I received my heat tape yesterday. This stuff is all that I had hoped for and more. I can't imagine a better way to incorporate heaters into a box. Apparently, these guys have done a lot of battery heating applications including something with Ford apparently. Anyways, I haven't received my SSR yet, but I installed a strip in one of my boxes and tried it on 120vac (while monitoring)... it worked great. This piece is about 2 feet long and draw was 0.3 amps so, about 36 watts on wall power. It's super easy to work with, just cut it with scissors and while there are proper fasteners, I just soldered leads onto the bus strips. I just used aluminum foil tape to fasten it on Al heat spreading sheet.


Hey DIY, How have these heaters worked out for you? Any issues? How are you controlling temperature, relay and thermostat? How have those thermostats you used on the battery terminals worked out? Do these just control the fans, or also the heaters? Seems they could be used with a 120VAC relay with 12VDC coil to control power to the heaters, no? I see Calorique has a "peel and stick" product that looks like it would work well fro adhering heaters to the back of an aluminum sheet, then cells on top, insulation underneath.
Edit: I see there is a 240VAC/10A version of the thermostat, rated for 100k switching cycles, so no need for a relay.


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