# Review of Headway Battery for the Big 13 Tractor



## Jimdear2 (Oct 12, 2008)

Hi all,

Hope you will all help out here. Our batteries and other stuff will be arriving on the 4th of January.

I'm going to describe the proposed battery pack/monitering system/charging system layout for the tractor and ask you for opinions.

Don't be afraid to lay it on me if you think somethin is a bad in the set up. I know in advance there are potential holes and problems. Some are irrellivant becaust this is a competition machine and will only run for 15 to 20 seconds at a time. Some I will live with because of cost andweight considerations.

I need to find any problems that I have missed in planning. LAY IT ON ME

Initially we will be using 150 38120P Batteries in a 50S/3P layout. Eventually we will be adding another layer if we find we need it and when we can afford it. 

Each set of 3 batteries (four later) will be buddy paralleled (similar to what JACKBAUER is doing).

Each buddy pack of three will be monitored by a Cell Log 8M. Eight buddy packs of three batteries to each Cell Log. This should keep us pretty aware of condition of each buddy pack. If we see a odd or out of spec pack we can look for a dud battery. The cell log will also give us warning if we exceed a low voltage we will decide on when we are pulling.

Each buddy pack of three batteries will be charged by a DC/DC converter, 5 volt in and each converter adjusted to 3.65 volts out. The DC to DC converters will be powered by a regulated 5 volt 350 +- 50 amp power supply. (I have found a number of these on ebay).

This way, no battery can be charged above 3.65 volts and if a buddy pack will not come up to spec. we can check the individual cells.

We never expect to do more then two consecutive runs within 15 to 20 minutes. The charger should restore the pack well enough between hooks.

20 inches wide x 6 inches thick x 50 inches long, about 100 pounds, a killer battery. 172 volts (3.45 voltsper cell) and 24ah nominal and up to 600 amps at I hope 2.6 to 3 volts per cell times 50 cells under load. Up to 90 kW. Oh Boy.

Y'all be well and have a great New Year.
Jim


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## rwaudio (May 22, 2008)

Which dc/dc converters are you going to use? I'm with you on that setup though! I would do some testing as to the current draw etc when you start to charge from various SOC levels. Otherwise your setup sounds good, I'm sure others will find the holes 
Good luck!


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## Jimdear2 (Oct 12, 2008)

My partner whom is the electronics wiz has them. All I know right now is they are 5 volts in and adjustible 3 to 4 volts out and I think he said 9 amps. I'll get names and numbers from him tomorrow if I can.

He has been using a jury rig with them to charge our test batteries. Seem to work quite well
Jim


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## frodus (Apr 12, 2008)

here are some 20A vicor's. They need a 48V front end.

http://cgi.ebay.com/VICOR-DC-DC-CON...889?pt=LH_DefaultDomain_0&hash=item45f51942f9

$10 each ain't bad. Seller might sell for less in higher quantities.


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## Jimdear2 (Oct 12, 2008)

frodus said:


> here are some 20A vicor's. They need a 48V front end.
> 
> http://cgi.ebay.com/VICOR-DC-DC-CON...889?pt=LH_DefaultDomain_0&hash=item45f51942f9
> 
> $10 each ain't bad. Seller might sell for less in higher quantities.


Frodus,

Thanks for the tip.

Darin has located something that run $3.50 in quantity. Just a board so we will need to box them, probably with the panel that will hold the Cell Logs. They are 5 volt input and adjustable output.

I plan on using something like this to power the DC to DC converters.

http://cgi.ebay.com/ACDC-Power-Supp...582?pt=LH_DefaultDomain_0&hash=item563c2ed106.

I've found a bunch of these ranging from $80.00 to $300.00 with outputs up to 450 amps and inputs from 100 to 240 volts, 50 and 60 hz.

Thanks and Happy New Year,
Jim


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## rwaudio (May 22, 2008)

frodus said:


> here are some 20A vicor's. They need a 48V front end.
> 
> http://cgi.ebay.com/VICOR-DC-DC-CON...889?pt=LH_DefaultDomain_0&hash=item45f51942f9
> 
> $10 each ain't bad. Seller might sell for less in higher quantities.


 
Here's the ones I'm using ($4.95 or less...), and they seem to perform pretty well:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=380195053685&ssPageName=STRK:MEWAX:IT

I have a temporary setup that works really well, I assembled the pack quite unbalanced to see how it would bring it in line, which it did very nicely.


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## Jimdear2 (Oct 12, 2008)

RW,

Your set up works well? Great that is encouraging. 

I have a question for you. It looks like you are using aluminium for your connecting buss. Are you having any heating problems. 

I was going to order the copper to make up my buss connectors tomorrow, but just the raw material was over $200.00. Aluminium should be quite a bit cheaper. I know aluminium will carry a lot of current and you need to size up at least 50% or more. Do you know of any rule on sizing?

Are you noticing any problems? It looks like you are powering audio AMPs and I know they will pull a LOT of current.

Thanks,
Jim


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## rwaudio (May 22, 2008)

Jimdear2 said:


> RW,
> 
> Your set up works well? Great that is encouraging.
> 
> ...


So far I have 1/2 a dozen cycles at different SOC and the dc/dc converters charge things nicely, I'm charging to 3.5V now. I started out at 3.65V but at over about 50% discharge it was drawing huge currents from the dc/dc converters (mine will put out 27-28A at slight overload) however dialing the voltage back a bit put me in a nicer current output even when the cells are quite discharged.

As for the aluminum, I'm using 1/8" and there is zero heat but I can only draw about 100A right now, I did use it to shart my Porsche as well but that was a very short burst. Like you said a 50% oversize isn't bad, the technical equivalent is more like +33ish% but 50% makes the numbers easy and actually increases the current capacity slightly over copper. The weight/size/cost makes it a decent alternative, just be aware of the properties of aluminum oxide. However if you start to compare what some little 90C lipo's are using (10 or 12awg copper) to carry their big currents, 1/8" aluminum starts to look huge!


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## Yabert (Feb 7, 2010)

Jimdear2 said:


> I have a question for you. It looks like you are using aluminium for your connecting buss. Are you having any heating problems.


For my motorcycle I used 11 Ga (0.091") aluminium bar to pass around 600A peak to the battery without problems. I use NO-OX-ID compound at terminal (contact area).
But my buss bar was large! 0.091" x 2" give a great area.

My understanding is: AWG 00 (2-0) copper wire have a 0.105" square of conductor area.
So 0.125 aluminium bar need to be 1-1/4" tall for have same resistance. (0.105" / 0.125" / 0.66 = 1.27")
And in your case, because you use 3P configuration, 1/8 x 1/2 bar will be electrically good but 1/8 x 3/4 will be structurally better!


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## Jimdear2 (Oct 12, 2008)

Yabert,

You may find this information supprising, I sure did.

I do admit that my original method of selection of the copper was a bit of research and a bit of gut. Probably I could get by with a bit smaller stock but Since most of the work this battery will do is full on have no mercy 20 to 25C, I wanted to err on the side of caution. 

I went to my metal supplier's catalog and looked up aluminium plate and bars with approx 50% increase in size. I was shocked to see the price of the aluminium was quite a bit higher then the smaller copper stock. To go with 50% bigger aluminium would have cost about 15% more.

Live and learn.

I still say the stuff you build is first quality.

Have a gooooooooooooood New Year,
Jim


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## rwaudio (May 22, 2008)

Jimdear2 said:


> Yabert,
> 
> You may find this information supprising, I sure did.
> 
> ...


That's interesting, based on the two metal suppliers that I use copper flat bar is roughly 7-9 times more expensive than the same size aluminum. What size copper/aluminum were you comparing? And if you don't mind where from?


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## Jimdear2 (Oct 12, 2008)

rwaudio said:


> So far I have 1/2 a dozen cycles at different SOC and the dc/dc converters charge things nicely, I'm charging to 3.5V now. I started out at 3.65V but at over about 50% discharge it was drawing huge currents from the dc/dc converters (mine will put out 27-28A at slight overload) however dialing the voltage back a bit put me in a nicer current output even when the cells are quite discharged.


RW, 
Please consider me a complete idiot when it comes to electronics, please keep that in mind regarding my questions. I probably know enough to just confuse everyone.

Help me if you can.

You say you are using 48 volt in, 3.3 volt out DC to DC converters but you mention charging at 3.65 volt and also 3.5 volts. How? Are you putting 2 units in series and then using resistors? Some other method?

When I look at your picture I can't quite figure what is going on. Can you sketch a diagram?

HERE IS MY PROBLEM

What I want to do is charge 50 individual 3 cell parallel packs with 3.5 volts to each pack. since the parallel packs are also connected in series and because I want to use a common power supply to power them, I'm told that the DC to DC converters MUST be isolated.

The advantage for me for not applying more then 3.5 volts to an individual 3 cell pack is safe charging that does not require monitoring. The 3 cell parallel packs will never recieve more then the DC to DC output of 3.5 volts. The current output can be low because normally the tractor will have at least a few days between competitions. 

I have a couple of options open for monitored bulk charging I won't need to go into here. 

My main concerns are:
1.) Plugging in the charging system and walking away, then returning to a balanced pack.
2.) Reasonable chance that I will not return to a burnt to the ground tractor and storage unit.
3.) Not being required to spend more then the cost of the pack for a BMS system and LiPoFe charger and then still have to worry about burning to the ground with unattended charging.

I will be monitoring each 3 cell parallel pack with Cell Log 8m units so I can set a high and low limit to shut down charging units but that requires monitoring. I want to be able to plug in the power supply and walk away knowing that no battery is going to get more then the output voltage of the DC to DC unit.

Do you know if the 3.3 volt and 3.5 volt DC to DC units he sells are isolated. I do not know where to go look for this information. Can you help?


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## Jimdear2 (Oct 12, 2008)

rwaudio said:


> That's interesting, based on the two metal suppliers that I use copper flat bar is roughly 7-9 times more expensive than the same size aluminum. What size copper/aluminum were you comparing? And if you don't mind where from?


 
McMasters-Carr is the supplier.

http://www.mcmaster.com/

Multi purpose copper 99.9% pure (Alloy 110)
3/4 inch wide strip, 1/8 in thick and 3 feet long. $14.59 each
2 inch wide strip, 1/8 inch thick and 3 feet long. $34.75 each
1 inch wide strip, 1/4 inch thick and 1 foot long. $11.00 each

Super-Corrosion-Resistant Easy-to-Weld Aluminum (Alloy 5052)
3/4 inch wide strip, 3/16 inch thick and 3 feet long. 21.38 each
2 inch wide strip, 3/16 inch thick and 3 feet long. $45.29 each
1 inch wide strip, 3/8 inch thick and 1 foot long. $14.93 each

Improved-Strength Basic Aluminum (Alloy 3003)
1 inch wide strip, 1/8 inch thick and 3 feet long. 21.38 each (no 3/4 width available in this length)
2 inch wide strip, 3/16 inch thick and 3 feet long. $44.77 each
1 inch wide strip, 3/8 inch thick and 1 foot long. $14.93 each


Total for 1 piece of each in:

Multi purpose copper 99.9% pure (Alloy 110) ............................$60.34
Super Corrosion Resistant Easy to Weld Aluminum (Alloy 5052)....$81.60
Improved Strength Basic Aluminum (Alloy 3003).........................$81.08

I'm sure I could do better, but McMasters-Carr has been my supplier of choice for years.

24/7 access
Super service, usually order to door in less then 36 hours at standard UPS rates
High quality material
They usually have what I need.
Their search functions are easy to use and fast.

So it was copper for me
Jim


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## toddshotrods (Feb 10, 2009)

I love McMaster for the amazing variety of hard to find stuff, but they're kind of high on metal - especially the small sizes. I buy most of my steel and aluminum supplies form Metals Depot.

*Aluminum*
1/8" x 1" x 4' 6061 - $4.52

3/16" x 2" x 4' 6061 - $11.88

3/8" x 1" x 4' 6061 - $10.56

Online Metals is another good one, but I haven't ordered from them yet. CFreeman54 has - that's where I got the link. They have copper for better prices than McMaster, and you'll notice a big discount for buying longer lengths. I like their site because it has a lot of info on the supplies, like weight per linear foot.


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## EVfun (Mar 14, 2010)

Since we are discussing sources I thought I would toss out a couple more. Metals Depot is a source I hadn't previously heard about, thanks Todd.

I often order from Online Metals. They are local to me so standard shipping is usually ends up being 2 days to door. I can also will call and pick it up in Seattle. 

I have ordered from Speedy Metals a number of times. I found this company before finding Online Metals. Since they are half way across the country from me it always takes a few extra days to get my order.


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## Jimdear2 (Oct 12, 2008)

Thanks to you all for the links, I have them in my Metals Suppliers folder of my Favorites Bar now. 

Copper prices from them all seem about right with McMasters-Carr, Aluminium is quite a bit less. I wonder why?

Jim


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## rwaudio (May 22, 2008)

Jimdear2 said:


> RW,
> Please consider me a complete idiot when it comes to electronics, please keep that in mind regarding my questions. I probably know enough to just confuse everyone.
> 
> Help me if you can.
> ...


Many of the dc/dc converters are isolated, but not all. If you have a part number for the dc/dc I would be happy to check it out. Also most dc/dc converters have an adjustable output (or trim) of about +/- 10% and some have a wider range. 3.3V + 10% is 3.63V (3.65 is safe) I dialed it back to 3.5v to stay closer to the rated output current. The voltage is set by the resistor you can see in the picture, when I design the board it will be a 20 turn pot to dial the voltage in exactly.



Jimdear2 said:


> When I look at your picture I can't quite figure what is going on. Can you sketch a diagram?


I believe my setup is exactly what you are trying to do, I have 3 parallel cells per group, with 4 groups in series (you'll have 50 but same idea) there is a dc/dc converter per group, now the wiring might look a bit odd though. The when you put all of the dc/dc converters in series to charge a series pack, almost all of the current flows through the large wires in the picture, so you are basically building a 175v power supply (50 x 3.5v dc/dc converters in series) the current will flow in one big circle, not 50 small circles. The only time current will flow through the small red wires (in my picture) is when the cells are out of balance. So when you build the charger it's better to use heavy connections between the + and - connections of the dc/dc converters and then run a wire to the cell (use heavy wire, not the small stuff I used) and fuse every wire at the cell end (VERY CLOSE TO THE CELL). 



Jimdear2 said:


> HERE IS MY PROBLEM
> 
> What I want to do is charge 50 individual 3 cell parallel packs with 3.5 volts to each pack. since the parallel packs are also connected in series and because I want to use a common power supply to power them, I'm told that the DC to DC converters MUST be isolated.


That is 100% true, if the dc/dc converters are not isolated it won't work and things will blow up.



Jimdear2 said:


> The advantage for me for not applying more then 3.5 volts to an individual 3 cell pack is safe charging that does not require monitoring. The 3 cell parallel packs will never recieve more then the DC to DC output of 3.5 volts. The current output can be low because normally the tractor will have at least a few days between competitions.


That's the exact reason I'm designing my system, there is minimal chance of overcharging a cell. The chances of a dc/dc converter failing and putting out higher than 3.5v is very slim. There is the chance of a dc/dc converter failing and a group of cells not getting charged, if that happens you will probably destroy them if it isn't caught before you make a run.



Jimdear2 said:


> I have a couple of options open for monitored bulk charging I won't need to go into here.
> 
> My main concerns are:
> 1.) Plugging in the charging system and walking away, then returning to a balanced pack.
> ...


1.) That is the same ideal I have, and providing a dc/dc converter doesn't fail it should be just that simple.
2.) There is minimal chance that a cell could be over charged (which is when they burn)
3.) Also the same reason I'm designing my system, a few grand for a charger, few grand for BMS, and few hundred for gauges isn't what I wanted to do. So my system will cover all of those for much less.

There are two negatives though, you are top balancing, so be careful not to go to 100% discharge or you could damage cells, and if a dc/dc converter fails you could easily destroy the cells that didn't get charged, so you need some way to monitor and confirm all cells got charged. (This could be as simple as an LED that turns on when the dc/dc converter turns on, with a blocking diode so that the cell can't turn it on) I will be doing individual cell voltage monitoring, but I'm thinking that some type of double check might not be a bad thing.


Jimdear2 said:


> I will be monitoring each 3 cell parallel pack with Cell Log 8m units so I can set a high and low limit to shut down charging units but that requires monitoring. I want to be able to plug in the power supply and walk away knowing that no battery is going to get more then the output voltage of the DC to DC unit.


I'm not convinced that some other system turning off the charger is a good idea. (meaning reliable, and failsafe) Especially when monitoring voltage, if I do go with a system that will turn off the charger it will be based on current draw on the 48v line that powers the dc/dc converters. (too high or too low and it will turn it off) But probably a simple timer or something like that as the failsafe. 



Jimdear2 said:


> Do you know if the 3.3 volt and 3.5 volt DC to DC units he sells are isolated. I do not know where to go look for this information. Can you help?


The dc/dc converter I use is isolated and they make it pretty clear in the description, it's usually not something you have to go digging for. (depends where you are getting them of course) if you give me a part number I'd be happy to check it out for you.


On a side note from your later posts, I've used onlinemetals for years and the service is exceptional. I would recommend them to anyone, I believe speedymetals is a bit cheaper but they aren't so friendly shipping to Canada.


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## Jimdear2 (Oct 12, 2008)

RW,

And any others willing to comment,

Attached is a (very) poor partial sketch of the wiring diagram of my proposed combined monitoring/charging system/battery unit. 

I want to inclose the 150 batteries, the 50 Dc to Dc units and the power supply wireing to the DC to DC units into a ventilated plastic case. Also there will be wiring for the 7 Cell Log 8m units.

The size of the battery would be 6.5 inches high to include the eventual 4th layer of batteries. It would be 20 inches wide and about 35 inches long with the cooling fans. It should weigh in the area of 110 - 120 pounds in its 3 cell pack version. It is designed to fit between the frame rails and under the seat of the tractor.

As I understand you, you are using the SynQor PQ48033QNA25NKS 48 volt in 3.3 and around 12 amps out converter. This is an isolated unit and through the use of trim resistors (or trim pot for accurate setting) allows the output voltage to be adjusted up to 10%+-.

What information I have been able to find on this board suggests that the input voltage can be from 36 to 72 volts DC. Could you confirm that?

I believe that is exactly what I want to build the battery system I show in the sketch. Do you agree.

If the above is true then I am golden and all of my wishes in the previous post are covered.

Thanks a HUGE bunch for your help,
Jim


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## rwaudio (May 22, 2008)

All of the above is correct, the dc/dc converters I'm using will put out 25A, voltage and all of that is correct.

From the sketch, I would change:
tie dc/dc converter + to the next converter - and use a single wire to run to the cell, same with the monitoring side, you are using 2 wires for every connection, the + of cell 1 is connected to - of cell 2, no need to use two wires they are already connected. In my system I will be using one wire (per cell) for monitoring/charging there is no need to add more spaghetti. Keep it as clean and simple as possible and it should work for a long time.


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## Jimdear2 (Oct 12, 2008)

rwaudio said:


> All of the above is correct, the dc/dc converters I'm using will put out 25A, voltage and all of that is correct.
> 
> From the sketch, I would change:
> tie dc/dc converter + to the next converter - and use a single wire to run to the cell, same with the monitoring side, you are using 2 wires for every connection, the + of cell 1 is connected to - of cell 2, no need to use two wires they are already connected. In my system I will be using one wire (per cell) for monitoring/charging there is no need to add more spaghetti. Keep it as clean and simple as possible and it should work for a long time.


RW,

Thanks, I had already planned on the one wire setup I just drew it this way for clarity.

That is as clear as my sketches are, does the phrase "Clear as Mud" come to mind.

Jim


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## Jimdear2 (Oct 12, 2008)

Well it appears that we finally have enough pieces to get started on our 175 volt 24 ah Headway battery.

The batteries are here and we have been testing them. We found 1 DOA out of 160 batteries, not bad. We got the battery blocks after a bit of a fubar in shipping so I could start roughing in the battery.

Yesterday I got the last 6 of the Cell Logs and the 55 DC to DC boards.

With all of the major pieces in hand;

IT LOOKS LIKE THEY WILL ALL FIT. 

WOW Is that a load off, some of it is a bit close but it will go just like I planned it.

I'm going to have to make up 50 sub boards from perf board to mount the DC to DC boards and route power in and out of the boards as well as give places to hook up test equip when troubleshooting.

Once those are made and on battery buddy packs, we will trim each board to an exact voltage. With this set up we *CANNOT* overcharge a cell and every cell will *ALWAYS* be in ballance or we will see the difference on the cell logs. The cell logs will give a warning if any pack within the 8 they monitor varies outside a set limit

Just to be sure we will hook up the Cell Logs with a high voltage warning of 4 volts, so if a DC to DC board goes bad the warning action will shut down the 48 volt supply.

That takes care of the High Voltage (4 volts as high voltage LOL) and cell balance. It still requires manual checking between units, but at this price you can't have everything. 

For LVC we will have the Cell Logs set to trip the alarm at 2.2 volts (to start). The alarm action we have chosen is a power cut back by adding resistance in parrallel to the throttle probably a 25 % cut back. 

I've attached a couple PDFs of drawing that give a basic look at battery construction and the sub board for the DC to DC.

The battery should be about 16 inches wide by 7 inches high and 28 to 30 inches long. Should weigh in about 110 pounds. 

We figure with the 50S/3P start up battery, we figure we will have enouh power to find out what the weak spots are. About 75kW (100 hp).

Later (next year) I already have every thing set to just add another 50 batteries into the parallel strings to go for 50S/4P, and if really needed we have the room to go to 60S/4P

Sorry they are 2D. I did it in Adobe Illustrator. I'veot to get a CAD program, a cheap one that works on Windows 7.

I'll be taking photos as I go and I'll post them as they apply.

Jim


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## rwaudio (May 22, 2008)

Hi Jim,

It looks good!
Your 48v bus is quite a bit different from mine so it looks weird to me, but if you keep it all isolated it should work well. 

Be careful of the spade connections to the cells though, 25A is a lot if your spade isn't seated nicely and making good contact. It would be a big problem if your voltage measured at the cell log point was different from the actual cell because of a bad spade. I had to go to minimum 12awg wire before the voltage drop at 25A was minimal across the wire. I would measure 3.5v (my charge voltage) at the dc/dc converter terminals and 3.3-3.4v at the cell terminals when I was using 16 or 18awg wire. Just make sure you use 10/12awg for these connections even though they are short.

I do like the fact that you should be able to just pull out a board and replace it in seconds if there was a failure. Just for piece of mind I would throw an LED on each cell board to indicate it's receiving 48v power as a quick visual that they are all charging. (it's better to put it on the output side of the dc/dc but a little more complex since the battery would power the LED unless you had a mosfet disconnect or other means of isolating the converter from the cells).

One other thing to be aware of, the dc/dc converter will actually draw about 5ma (I think it was 5ma, you may want to measure it) from the cells if the converters are still connected but turned off. Just be aware of this for long term storage. To eliminate this I'm designing a mosfet switch into my boards that disconnects the negative terminal of each converter when the charger is off, this also allows me to put an LED on the output side easily that will only turn on when the dc/dc converter turns on.

For your output voltage tweaking, I would suggest a 20turn pot. I used 1% resisitors for testing and there was upto a 0.03v difference in voltage from different converters. The resistors measured pretty darn close on the meter, so there could be some variance in the dc/dc converter itself but a 20 turn pot lets you get everything exact to as many decimal places as your meter is capable of.
http://www.dipmicro.com/store/R4V10-3296

Do you think there will be any vibration problems related to the rigid board/cell mounting? You've probably noticed the dc/dc converters are pretty heavy little suckers.


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## Jimdear2 (Oct 12, 2008)

rwaudio said:


> Hi Jim,
> 
> It looks good!
> Your 48v bus is quite a bit different from mine so it looks weird to me, but if you keep it all isolated it should work well.


rw,

Man you are good! ! ! Every concern and weak point in my design that has me worried, you hit on it. Lets see if you agree on my reasoning. I cover the 48 volt buss structure at the end of the post.

I do have a question since these boards are tolarent to input voltage from like 32 to 76 volts. I was wondering if it might not be wise to up the input to 60 volts? That should lessen the load current and heat.

Have you tried doing that with your prototype system? I have enough extra stuff that I'm going to prototype a 3 battery stack and board and try it out, if you haven't already.



rwaudio said:


> Be careful of the spade connections to the cells though, 25A is a lot if your spade isn't seated nicely and making good contact. It would be a big problem if your voltage measured at the cell log point was different from the actual cell because of a bad spade.


I'm using good quality tinned copper male and female spades. I had planned on soldering as well as bolting the male spades to the 1/8 x 3/4 inch copper bars that parallel connect the buddy packs, on the board side the Female spades will be pop rivited with copper rivets to the boards and the + - 3.55 volt leads from the DC to DC will be soldered at each end. I was going to go with 14 awg but I'll go with 12 on your recommendation. OEMs regularly run 40 amps through these spades in fuse boxes and relays also there will be continious airflow. I hope that's enough



rwaudio said:


> I had to go to minimum 12awg wire before the voltage drop at 25A was minimal across the wire. I would measure 3.5v (my charge voltage) at the dc/dc converter terminals and 3.3-3.4v at the cell terminals when I was using 16 or 18awg wire. Just make sure you use 10/12awg for these connections even though they are short.


There was some thought about that, for starters we are tying the sense pin #5 to the out put pin at the board but I'm thinking of adding a male spade to the #3 battery connection in the parallel stack (remember the 4th battery is not installed yet so it's easy to get to) to measure from as well as tie to the sense pin to if needed and let the board push to compensate for any minor differences



rwaudio said:


> I do like the fact that you should be able to just pull out a board and replace it in seconds if there was a failure. Just for piece of mind I would throw an LED on each cell board to indicate it's receiving 48v power as a quick visual that they are all charging. (it's better to put it on the output side of the dc/dc but a little more complex since the battery would power the LED unless you had a mosfet disconnect or other means of isolating the converter from the cells).


I do like the led idea, I was even considering it, but for the sake of simplicity I decided to go with just watching the cell logs for now. Might do this for version two next year when we add the 4th layer of batteries. 



rwaudio said:


> One other thing to be aware of, the dc/dc converter will actually draw about 5ma (I think it was 5ma, you may want to measure it) from the cells if the converters are still connected but turned off. Just be aware of this for long term storage. To eliminate this I'm designing a mosfet switch into my boards that disconnects the negative terminal of each converter when the charger is off, this also allows me to put an LED on the output side easily that will only turn on when the dc/dc converter turns on.


Right now we have pin two tied to pin three which is 48 volt neg. So the board should be off when there is no power in the 48 volt buss. The doc.s say this term has to be pulled low to turn on the board. Am I wrong or missing something? If Iam I would appreciate your advise and if you would be willing a look at your circuit. Remember *I'm Not Electronic. *Do understand you to say that the board will still draw 5ma from the battery even with the board turned off, i.e. Pin #2 open?. If it does, for now we will just have to keep the system charged during the season. We normally charge before we leave to a pull and top up just before each hook to warm the batteries. For winter storage I'll pull the boards once we reach storage voltage.



rwaudio said:


> For your output voltage tweaking, I would suggest a 20turn pot. I used 1% resisitors for testing and there was upto a 0.03v difference in voltage from different converters. The resistors measured pretty darn close on the meter, so there could be some variance in the dc/dc converter itself but a 20 turn pot lets you get everything exact to as many decimal places as your meter is capable of.
> http://www.dipmicro.com/store/R4V10-3296


I'm also in the trim pot corner, my buddy thinks he can get resistors of sufficent tolerance to go simple. I bet we end up with pots. Your source seems reasonable. I'll pass the info on to him.



rwaudio said:


> Do you think there will be any vibration problems related to the rigid board/cell mounting? You've probably noticed the dc/dc converters are pretty heavy little suckers.


Vibration and power draw through the 48 volt buss has been a BIG concern for me. thats why I thought of a piece of brass threadded rod of approximatly the same diameter as the #10 awg wire I was going to use. Thinking the rod should offer enouge support while carrying enough current to handle 5 battery buddy packs. That why I'm using 10 parallel supply buss sets. Each 5 pack parallel buss will be tied to the 48 volt supply(s) through 8 Gauge wire

I didn't show it in my drawing (got tired last night and missed it) but as the threadded crosses each plastic battery block I planned to pot it with a good quality silicone. 

Lastly, again not in the drawing, the entire battery tray will be supported on rubber mounts the type that is a barrel of rubber with a plate and bolt bonded to each end.

Did I miss any of your concerns. I still like the led on the board idea and may go with it anyway.

Please let me know more about the mosfet shut off and LED system.

Thanks for your help.

I don't know if you have been monitoring the BMS or NOT to BMS thread. I wish more of those guys would look at this set up. For less money then these guys are willing to invest in their charger, we have it all, a failsafe overvolt protection, good cell voltage monitoring and LVC cut off protection.

Go Figure!

Jim


----------



## jackbauer (Jan 12, 2008)

Sadly Jim it seems people are much more likely to try and talk a problem to death these days then get up and try something. I'm in the same boat as yourself with the headways and asked on various forums and while i have gotten a few good gems of information all too often it degardes into he said she said


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## rwaudio (May 22, 2008)

Jimdear2 said:


> rw,
> 
> Man you are good! ! ! Every concern and weak point in my design that has me worried, you hit on it. Lets see if you agree on my reasoning. I cover the 48 volt buss structure at the end of the post.
> 
> ...


Hi Jim,
I had contemplated using the upper end of the input voltage range as well however if you look at the data sheet, the power disipation is higher at higher input voltages. From what I read there are two stages of power conversion in these converters, first it takes 36-75v and converts it down to some middle value IE 20v (I don't know so I'm just guessing) There is more wasted heat/power when converting 75v to 20v than converting 36v to 20v. There are some drawback of such a wide input voltage as not ever input voltage can be "optimum". Then it takes that 20v (remember a guess only) and converts it down to 3.3v.

I've personally only tested at 48v since that is the type of power supply I was able to find in good quality at a good price. Regardless of input voltage you choose, the power will be roughly the same. Based on the data sheet it's like 2.6A input at 36v which would mean in the ballpark of 1.3A input at 75v (same power though) This looks pretty realistic since at 48v in and a slight overload on the output of about 27-28A the input current was around 2.13-2.2A



Jimdear2 said:


> I'm using good quality tinned copper male and female spades. I had planned on soldering as well as bolting the male spades to the 1/8 x 3/4 inch copper bars that parallel connect the buddy packs, on the board side the Female spades will be pop rivited with copper rivets to the boards and the + - 3.55 volt leads from the DC to DC will be soldered at each end. I was going to go with 14 awg but I'll go with 12 on your recommendation. OEMs regularly run 40 amps through these spades in fuse boxes and relays also there will be continious airflow. I hope that's enough
> 
> 
> 
> There was some thought about that, for starters we are tying the sense pin #5 to the out put pin at the board but I'm thinking of adding a male spade to the #3 battery connection in the parallel stack (remember the 4th battery is not installed yet so it's easy to get to) to measure from as well as tie to the sense pin to if needed and let the board push to compensate for any minor differences


If possible I would use the sense wires, I was able to make up for the drop in 18awg wires by using the remote sense wires, however those 18awg wires got pretty warm.



Jimdear2 said:


> I do like the led idea, I was even considering it, but for the sake of simplicity I decided to go with just watching the cell logs for now. Might do this for version two next year when we add the 4th layer of batteries.
> 
> 
> 
> Right now we have pin two tied to pin three which is 48 volt neg. So the board should be off when there is no power in the 48 volt buss. The doc.s say this term has to be pulled low to turn on the board. Am I wrong or missing something? If Iam I would appreciate your advise and if you would be willing a look at your circuit. Remember *I'm Not Electronic. *Do understand you to say that the board will still draw 5ma from the battery even with the board turned off, i.e. Pin #2 open?. If it does, for now we will just have to keep the system charged during the season. We normally charge before we leave to a pull and top up just before each hook to warm the batteries. For winter storage I'll pull the boards once we reach storage voltage.


And LED and a resistor is dirt cheap, if you have the room I would add it. (this also assumes you would be able to see the boards for visual confirmation)


Jimdear2 said:


> I'm also in the trim pot corner, my buddy thinks he can get resistors of sufficent tolerance to go simple. I bet we end up with pots. Your source seems reasonable. I'll pass the info on to him.


I just ordered 100 of those pots for my setup, and I've used tons of Bourns pots in the past and they are good quality. Shipping isn't the fastest but the price is unbeatable.


Jimdear2 said:


> Vibration and power draw through the 48 volt buss has been a BIG concern for me. thats why I thought of a piece of brass threadded rod of approximatly the same diameter as the #10 awg wire I was going to use. Thinking the rod should offer enouge support while carrying enough current to handle 5 battery buddy packs. That why I'm using 10 parallel supply buss sets. Each 5 pack parallel buss will be tied to the 48 volt supply(s) through 8 Gauge wire
> 
> I didn't show it in my drawing (got tired last night and missed it) but as the threadded crosses each plastic battery block I planned to pot it with a good quality silicone.
> 
> ...


Your current at 48v shouldn't be that high, each dc/dc converter should draw a maximum of 2A and that would be at full load, that's 48V and 100A, (this assumes you have a power supply that can put out 100A at 48V, mine will only do 60-65A at 48V) since it looks like you will have a bunch of seperate power runs each feeding a group of converters the currents shouldn't be too high. 



Jimdear2 said:


> Thanks for your help.
> 
> I don't know if you have been monitoring the BMS or NOT to BMS thread. I wish more of those guys would look at this set up. For less money then these guys are willing to invest in their charger, we have it all, a failsafe overvolt protection, good cell voltage monitoring and LVC cut off protection.
> 
> ...


I've been in the thread too, it's kind of funny how everyone assumes some things will fail and others won't. Sure the chances of component failure go up with you have 50-100pcs of something, but I would much prefer a failure that results in a few headway paper weights, instead of a failure that creates headway fire crackers.

The cost also blows me away, my setup for 90-97 series cells including custom PCB's, power supplys, dc/dc converters, all the parts and the microcontroller to tie it all together will be $1200-1500, that includes a 3kw charger that can't overcharge, a BMS system that doesn't require shunting to balance every time, and a monitoring system that can be tweaked and added to as I want. 
Sure it's more work than an off the shelf Manzanita/Zivan/Elcon + minibms/other + monitoring system. But it comes in around the same price as the minibms alone for my ~97 cell setup. 

Not to mention the fact there is a 50A version of the dc/dc converter we are using, and any of them could be put in parallel for higher currents. If you had a really high current 36-75v source (battery bank?) you could charge a pack like ours in minutes instead of hours. There is a small efficiency penalty compared to a Manzanita or something similar though, since we have two stages of power conversion however it's safer/cheaper/and adjustable.


----------



## JRP3 (Mar 7, 2008)

jackbauer said:


> Sadly Jim it seems people are much more likely to try and talk a problem to death these days then get up and try something.


Talk is cheap


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## Jimdear2 (Oct 12, 2008)

JRP3 said:


> Talk is cheap


JRP3 and rwaudio and Jack,

Man I wish this battery, charging and monitoring system was as cheap as the talk over there has been. 

Almost 40 pages and they are still talking, nothing has been settled.

Jim


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## Jimdear2 (Oct 12, 2008)

rwaudio said:


> I've personally only tested at 48v since that is the type of power supply I was able to find in good quality at a good price.


RW,

Right now I'm going to use my Lester 48 volt charger and four 12 volt batteries as a power source. I've been looking at 48 volt power supplies until I'm blue in the face. 

Im looking for something with adjustable output say 0 to 60 volts, 20 to 40 amps and variable 100/240 or so input and 50/60 hz. 

If you don't mind, what did you end up with.

I've found a few that are close to my ideal but nothing I really liked. Maybe one like yours would be the dream machine.

Jim


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## JRP3 (Mar 7, 2008)

Jimdear2 said:


> Almost 40 pages and they are still talking, nothing has been settled.


It's actually been a pretty good discussion. Some people are hotheads but overall we've kept it between the lines. It's an interesting contrast between people basically saying it's impossible to do what some of us are doing. What you are working on is an interesting solution, I'm happy to watch you work it out and test it's performance  My basic premise is in line with what the battery expert Jay says, get closely matched cells, don't cycle them deeply, and don't bother with automated management. I think that's easier to do with the large format prismatics from CALB than the smaller cells from Headway.


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## rwaudio (May 22, 2008)

Jimdear2 said:


> RW,
> 
> Right now I'm going to use my Lester 48 volt charger and four 12 volt batteries as a power source. I've been looking at 48 volt power supplies until I'm blue in the face.
> 
> ...


Jim,

My power supply isn't adjustable (well +/- a few volts but that's it) however it's industrial quality and just like the dc/dc converters in surplus it's very cheap compared to it's value when new.

Have a look on ebay for Power-one HPF5, I'm using a pair of HPF5D2D6A8A1's not the ideal solution because I have to do a little creative wiring to get 48v out of it and use them in pairs but the modules are isolated and rock solid. They were NOS still sealed in the factory packaging and cheaper than virtually any new 2000watt power supply, in the configuration I'm using each one will put out 1500w so I will enable one when I plug into 120v and both when I plug into 240v.

This one would be a great solution:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=280387194679&ssPageName=STRK:MEWAX:IT#ht_2278wt_905

I tried to contact the seller many times to ship to Canada but no response. So I was forced to try a different (less ideal) version, but the end result will be virtually the same.


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## Jimdear2 (Oct 12, 2008)

JRP3 said:


> It's actually been a pretty good discussion. Some people are hotheads but overall we've kept it between the lines. It's an interesting contrast between people basically saying it's impossible to do what some of us are doing. What you are working on is an interesting solution, I'm happy to watch you work it out and test it's performance  My basic premise is in line with what the battery expert Jay says, get closely matched cells, don't cycle them deeply, and don't bother with automated management. I think that's easier to do with the large format prismatics from CALB than the smaller cells from Headway.


JRP3,

As far as what I'm doing with the Headways, it is kind of an experiment on something that is directly appliciple to large format prismatics. I've thought for years that this whole monitoring, balanceing, finicky thing with batteries was the wrong way to do EVs. I'm using the Headways because I can get big power out of a low weight battery for my chosen venue. But the end result will be 4 battery parallel stack, that would be like 32 ah prismatic and applicable to large batteries.

My feeling is that it is the OEMs responsibility to make sure you cant overfill your battery with out deliberat effort, just like the ICE people make sure you can't over fill a fuel tank. That expansion volume is pretty much untouchable you know. 
Yes, a lot has been said in that thread and there were some real good nuggets of information. It seem to be stagnating now with a flash of real information evey once in a while.

I've expressed my feeling on the battery/charging/monitoring situation before. I've always felt that a manufacturer who sells something a finicky as these things are, has some responsibility to make them, if not fool proof, at least reasonable useable without a degree in rocket science.

Something like these batteries, that can be easily damaged when bulk charged with a single charger, because of a very small variation in voltage should have some form of protection built in. I don't think it's the OEMs responsibility to prevent abuse such as over discharge, but having batteries damaged by recharging is stupid. That is normal intended use. 

Monitoring and abuse protection is an end user thing. Protecting the product from normal use, is an OEM thing. The really dumb thing about this is the OEM can include a small board like the ones I and rwaudio are using for a couple of dollars on the large prismatics that cost hundreds each and SOLVE the whole top balance, overcharge problem. As well as ending the need for $1000.00 plus chargers that still fail and damage packs. I beleive a competent EE with knowledge in the LiPo field could build a on battery board that would control the recharge like the DC to DC boards we are using plus by adding a unique ID code to each board allow a central unit to watch over the batteries on a CAN buss and just turn on a warning light and store a code (sound like OBD) whenever a problem happened.

A few of us getting together could write the specifications that an EE would need to design a common central unit and a on battery card that would be pretty universal even to battery count. None of this 8 battery monitoring central board that cost hundreds and you need XX of them then all of the on battery band aids. Every one wants to talk about board failures. Well the ones we are using have a 5 million hour MTBF, They are surplus, but they are costing $5.00 each.

If the battery OEM included them in the battery itself and said yes our or this version battery costs more but you get a central monitoring unit and a built in charging/balancing system with any count of any amprage batteries you buy. And these batteries that can be charged with any charger that can supply a voltage between X and Y. Sound interesting?

In the end, if they are going to use the large prismatics in production vehicles they will have to come up with something like that. The battery chargeing and maintenance should be pretty much transparent to the average end user. EVs are going to be a step backwards for a while, back to the days when a car owner HAD to know some things.

End of my battery charging rant.
Jim


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## Jimdear2 (Oct 12, 2008)

rwaudio said:


> Jim,
> 
> My power supply isn't adjustable (well +/- a few volts but that's it) however it's industrial quality and just like the dc/dc converters in surplus it's very cheap compared to it's value when new.


rw,

This is an example of what I've been looking at other then the real expansive lab power supplies that go for 400 or better.

http://cgi.ebay.com/Tyco-NP1200-48-...076?pt=LH_DefaultDomain_0&hash=item4aa73bd0e4 




rwaudio said:


> Have a look on ebay for Power-one HPF5, I'm using a pair of HPF5D2D6A8A1's not the ideal solution because I have to do a little creative wiring to get 48v out of it and use them in pairs but the modules are isolated and rock solid. They were NOS still sealed in the factory packaging and cheaper than virtually any new 2000watt power supply, in the configuration I'm using each one will put out 1500w so I will enable one when I plug into 120v and both when I plug into 240v.
> 
> This one would be a great solution:
> http://cgi.ebay.com/ws/eBayISAPI.dl...194679&ssPageName=STRK:MEWAX:IT#ht_2278wt_905
> ...


Very attractive except "Costa Rica" part is scarry . . . and a month delivery time, OUCH. 

I did search on the Power-one HPF5 and saw some listings I liked. I will keep looking. I guess I'll go with the four 72ah Powersonic telco ups batteries and my trusty lester 48 volt charger. The charger keeps the pack up and the pack dumps to the tractor battery.

Thanks for your input,
Jim


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## JRP3 (Mar 7, 2008)

I agree that a factory built and tested unit would be the best solution. That does not exist so people are trying to create one on their own. Unfortunately some of these have failed and have killed cells. Until a proven reliable system is available I'm not interested in using my cells as guinea pigs and paying for the privilege. If the cells are close enough in capacity bulk charging really works quite well, and now that we are getting cells with 1% variation from CALB it will be even better. A BMS is an attempt to make up for mismatched cells, the real solution is perfectly matched cells. At some point we get close enough that perfection isn't necessary. A bad cell should be such an anomaly that a monitoring system would be all that is necessary to flag it for replacement as opposed to active management to try and compensate. We might not be there yet but I think that's where we are headed.


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## Jimdear2 (Oct 12, 2008)

JRP3,

I agree with everything you say as long as bulk charging is kept below the knee of the charge curve. 

This shipping of matched cells is a good example of OEMs trying to make their product useable without thinking/worrying about it I.E. transparent.

In the end though, the OEMs will have to put controls on their systems that prevent active stupidity from damageing their products (and the active stupid people). If they don't we will have more situations like A123, as I understand it, just a few active stupid people killed DIY use of that product. 

In the end the responsible manufactuer has to put the top and bottom of the charge curve out of bounds by somehow.

I also bet the need some people have, to extract the last erg of energy from the battery is probably the biggest killer of cells out there. Sometimes the knowledge that DIY people have can bite us in the a$$.

"Just a little bit more should be OK" is right up there with other Famous Last Words.

Ah well, after reading all the news about and seeing the rate OEM car people are jumping on electric vehicles, the DIY basic transprotation car is going to go away fast. We're all going to become another bunch of those "DARN (ELECTRIC) HOT RODDERS"


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## rwaudio (May 22, 2008)

Jimdear2 said:


> I did search on the Power-one HPF5 and saw some listings I liked. I will keep looking. I guess I'll go with the four 72ah Powersonic telco ups batteries and my trusty lester 48 volt charger. The charger keeps the pack up and the pack dumps to the tractor battery.
> 
> Thanks for your input,
> Jim


I think that's a good solution, if I had the room/money for a 48v pack that could store enough energy to charge my pack I would do the same, especially if I could charge it from solar. For you it's great since you won't really be pulling that much energy out of the pack every run, it shouldn't be too hard to top up, and quite quickly as well.


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## Jimdear2 (Oct 12, 2008)

rwaudio said:


> <snip> if I had the room/money for a 48v pack that could store enough energy to charge my pack I would do the same, especially if I could charge it from solar. <snip>


RW,

What we both would probably like at home is a good solar array and one of these

http://cgi.ebay.com/48-VOLT-INDUSTR...831?pt=LH_DefaultDomain_0&hash=item3eff02822f 

Jim


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## rwaudio (May 22, 2008)

Jimdear2 said:


> RW,
> 
> What we both would probably like at home is a good solar array and one of these
> 
> ...


Yep, that would probably do the trick!

I remember back in the day when I was big into the Car stereo SPL competitions there was a Chevy Astro from Seattle that had a forklift battery configured for ~16v powering the stereo. 

I've mentioned what a LiFePO4 battery could do for them now, but they wouldn't believe it would beat something like a yellow top Optima, or a few of the other "stereo" batteries.


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## Jimdear2 (Oct 12, 2008)

rwaudio said:


> Yep, that would probably do the trick!
> 
> I remember back in the day when I was big into the Car stereo SPL competitions there was a Chevy Astro from Seattle that had a forklift battery configured for ~16v powering the stereo.
> 
> I've mentioned what a LiFePO4 battery could do for them now, but they wouldn't believe it would beat something like a yellow top Optima, or a few of the other "stereo" batteries.


You can still get big power from Pb look, at Hawkers, but . . . man you pay a penalty in moving it around.

Moving it is one thing, then there is the fact you need 50% + more battery voltage (weight) to compensate for peukert and the Internal Resistance voltage drop. It gets to the point where the car can't move the batteries.

People tend to stay with what they know works. A lot of the people in that venue (like most venues) are followers. Very few are inovators and those smart, skilled, people usually get dollared out by the also rans who have more money then skill.

As soon as people start winning shows with drivable cars that aren't one big battery box, they will go over to the High Output lithium. Look at some of those RC packs, less then a pound 6.? volts, 2 ah and 90+C for minutes.

Just between you and me I thought about them for a short while for the pulling tractor. Lots of power for short duration, low weight, fast recharge, almost perfect, but in the end just too fragile and never mind expense.

Jim


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## rwaudio (May 22, 2008)

Just a random observation.

My 12v pack has sat for atleast a few (3) weeks, possibly a month. I know there is parasitic draw because the dc/dc converters are directly connected so I wanted to measure the voltage.
the outer two cell groups (connected to +/- output terminals) are at 3.33v and the inner two cell groups are at 3.30v, everything was of course charged up equally.

Just something to watch for if you happen to charge, wait for awhile without topping up then discharge deeply (I'm sure you would be topping up first, but in the odd chance you don't for testing or something) there might be an imbalance. Might be enough reason for the mosfet disconnect when the charger is off, I'll keep an eye on it and see, and take some current readings when the dc/dc converters are setup in a series configuration.

However measurements after roughly 1 week, all cells were exactly the same to the accuracy of my meter.


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## rwaudio (May 22, 2008)

rwaudio said:


> Just a random observation.
> 
> My 12v pack has sat for atleast a few (3) weeks, possibly a month. I know there is parasitic draw because the dc/dc converters are directly connected so I wanted to measure the voltage.
> the outer two cell groups (connected to +/- output terminals) are at 3.33v and the inner two cell groups are at 3.30v, everything was of course charged up equally.
> ...


Ignore that, it's time for me to invest in a new DMM. When I measure with the black wire connected to negative and red wire connected to positive I get a different reading than when I swap the leads. It's consistently wrong lol. However measuring + to + and - to - on every cell I get exactly the same reading per cell. Battery is maintaining perfect top balance. I'm contemplating putting this pack in my F150 (5.4L V8), the stock battery isn't happy in this cold weather. Just to see how it handles the cold, and in the truck reduced capacity doesn't really matter, it's just the ability to put out enough current without too much voltage sag.


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## Jimdear2 (Oct 12, 2008)

Hi all,

Finally able to get back to the battery/charging/monitoring system we have been building and plan to mount on the Big 13 pulling tractor.

We finalized the prototype charging board and collected the necessary parts. See photos of the prototype board and test battery paralleled buddy stack.

We started building the boards today, each one takes about 15 minutes so we got 10 done today (started snowing so we had to quit early) only 40 more to go.

We also got started building the battery, we got 3/5 done and started to have problems with the Headways. By the time we had installed 90 batteries we had 9 batteries that the negitive terminal would turn in the case long before the batteries could be tightened, they would turn with only 2 or 3 inch pounds of torque. Even had two of the nine shatter the epoxy that is suppose to secure that end at about 5 or 6 inch pounds.

Anybody else experience this?

The charger board will take in 36 to 72 volts through the two spade connectors on top of the board, route it throught the DC to DC and then pass the voltage and current to the parallel battery stack through the spade terminals on the ends of the board to the buddy buss bar. 3.XX volts at up to 20 amps.

If you look close you will see a 20 turn variable pot on the board. This allows us to set each board to an exact voltage. We are considering 3.55 to 3.6 volts to start out. The beauty of this setup is it is impossible to overcharge a battery. As soon as the charger reaches the set volts it just sits there. 

The cell logs which hook up to the screw terminals on the board allow us to monitor each battery stack so when they all reach set voltage we know they are charged and top balanced. The protype allowed the battery to return to 3.4 volts in a few minutes.

Think about this; Put 48 volts at 20 amps into the charger buss. That is 960 watts, converted to 3.5 volts is 274 amps available to the battery divided by 50 parallel stack chargers, thats almost 6 amps per stack 

We should have the basic battery with charger boards done and in it's carrier frame next week end. I'll measure it up for the plexi covers so I can get the plastic shop to make them up.

More as we go along.

Jim


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## rwaudio (May 22, 2008)

Hi Jim, looks good!
Nice to see your setup is progressing. I hope your experience with the headways isn't common, are you going to return the bad cells? Is it worth it? So is the problem just bad threads?


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## Jimdear2 (Oct 12, 2008)

rwaudio said:


> Hi Jim, looks good!
> Nice to see your setup is progressing.


RW,

Yeh, it's good to get back at it, Health issues held me up for a while.



rwaudio said:


> I hope your experience with the headways isn't common, are you going to return the bad cells? Is it worth it?


I bought my cell from Manzanita Micro, they offer no warrenty other then DOA. I'm sure that if I tried to return them they would say we overtightened them. I have 45 years as a master mechanic and aircraft mechanic. I know how to tighten things.

I have been waiting a month for replacement of the one DOA I sent back on their RMA. 



rwaudio said:


> So is the problem just bad threads?


It's not the threads, it is the end plug that the threads are in. It looks like a bad bonding of the epoxy on the negitive end. We have two batteries that the epoxy shattered when the end moved. we are going to try to repot those two and see how it turns out. If it works we will dig out the old epoxy and put in new on the other seven. JB Weld wll fix anything.

We load checked the batteries and they still appear to be good.

How is your project comming?


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## JRoque (Mar 9, 2010)

Hi. Very nicely done! I've been thinking along these lines of using smaller, lower voltage "chargers" in groups of cells instead of one big box that might cook up your cells if it goes unchecked.

One thing I read on an early post here about the bus voltage vs dissipation, the closer your bus is to the output, the lower your wasted energy will be. As long as you meet the minimum input requirement of the DC-DC (and be above your output potential, too), you should be good. Typically with a DC-DC, the output current will not increase if you increase the input voltage; but losses will.

JR


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## Jimdear2 (Oct 12, 2008)

Jimdear2 said:


> RW,
> I bought my cell from Manzanita Micro, they offer no warrenty other then DOA. I'm sure that if I tried to return them they would say we overtightened them. I have 45 years as a master mechanic and aircraft mechanic. I know how to tighten things.
> 
> I have been waiting a month for replacement of the one DOA I sent back on their RMA.


To clarify two unfair statements in the above.

I was aware that there was no warrenty beyond two weeks when I bought the batteries and was just being cranky when I made the statement "I'm sure that if I tried to return them they would say we overtightened them." I did not bother to contact them because the No Warrenty statement was made very clear when I purchesed the bateries.

I've had, in a 45 year career of auto and aircraft repair, many countermen and sales people try to pass that canard on to me when I returned an obviously defecive part. Just facing possible hundreds of dollars in bad cells with no recourse but trying to get someone in China to honor their product made me lash out.

I have been waiting a month for replacement of the one DOA I sent back on their RMA.

This one is a mystery, I paid extra to the USPS for Prioity mail, 3 to 5 day delivery. Manzanita seems to have recieved it in something like three weeks. I will take this up with the USPS. 

I will admit that Clarice's statement that she "just found it in the mail box" after I questioned her about the delay could be misinterpreted and of course being the cranky old phart I am, I did. Clarice, sorry, being locked up in this house for the last month is turing me sour.

Manzanita has contacted me and we are trying to resolve the issues.

I apologize to the forum membrs for giving incomplete/wrong info and to Manzanita for not giving them a chance


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## Jimdear2 (Oct 12, 2008)

HOO RAY 

The battery is assembled, all 150 cells are in the plastic blocks. That's 50 3 cell buddy pack in series. If you look at the photos below you can see the 3/4 inch by 1/8 inch buss bars that make up the buddy packs in between the cells. At the very top of each buss bar are 2 spade connectors that the DC to DC chargers will plug into. A stainless 6mm x 12mm set screw is used between each battery with the buss bars sandwiched between the batteries.

You will also notice that there is room for one more layer of 50 batteries. (Next Year We Hope)

There is a metal angle iron frame that the battery sits in currently under construcrion.

One of the photos shows the 800 amp circuit breaker in its final position, it mounts to the metal battery frame and the plexi end cover. There will be 1/4 inch plexiglas panels at each end and a plexi cover over the top.

The battery is 30 inches long by 16 inches wide about 7 inches high and weighs in around a hundred pounds. I'll get an accurate weight later. The support frame is 36 inches long to accomadate the circuit breaker and wiring. 

The battery is designed to be easily movable so it can be shifted forward and back in the frame to help with set up for traction.

Each stick of batteries will be tied to the next with the double row tie plate that can be seen in one photo. The most positive and most negitive ends of the battery will have single row 1 x 1/4 inch buss bars with a 3/8th inch bolt to connect to the breaker and controller.

One photo shows 5 of the 50 charger boards. There will be one board for each buddy cell stack. Each of the charger boards is adjusted to output 3.500 volts maximum, and will pass up to 25 amps. Each board is powered from a 48 volt DC buss. The charger boards have a DC to DC converter board installed and the necessary circuitry to keep the voltage and current under control. Ate up a couple of DC to DC boards finding how to keep the current in check after a deep discharge. 

With this setup it is impossible to overcharge a battery and each full charge bring all cells into balance. When all batteries are stable and at the same voltage, charging is complete. We haven't tried yet but it looks like we can just keep a 48 volt source connected and the batteries should stay perfectly balanced. We'll see . . .

The remaing monitoring and the LVC functions will be handled by CellLog-8M units. You can see the wiring attachment block just next to the trim pot used to adjust the output voltage of each unit. The charging voltage, nominal voltage/balance and low voltage warning will output from the CellLog units. The Low Voltage alarm will trigger a throttle reduction event, it may be done in the controller or the throttle depending on the final design of some equippment.

We should be doing final fitment to the tractor by the first of March.

Going to be a fun ride.

Jim


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## Huub3 (Aug 16, 2009)

Jim,

that really looks impressive. Looking into Headway myself, and your build is a good motivation to proceed (nothing ordered yet).

I have two questions:
- the way you have build the pack, are these orange parts, and the mounted buss bars not blocking the mounting of the fourth row?
- in your opinion, can these batteries be mounted on the buss bars alone, so without these orange parts?

I have an idea for a mounting principle, in which simple parts and some cut metal and plastic can make a solid battery case, with all the wiring integrated. However, this idea builds on the fact that the batteries are mounted at their ends, e.g. the buss bars.

Curious about your opinion in this.

Regards,


Huub


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## JRP3 (Mar 7, 2008)

From what I've read about the end terminals I wouldn't stress them as a load bearing member. I'm sure some have done it but it sounds as if they can break fairly easily sometimes even when using the recommended tightening torque.


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## Jimdear2 (Oct 12, 2008)

Huub3 said:


> Jim,
> 
> that really looks impressive. Looking into Headway myself, and your build is a good motivation to proceed (nothing ordered yet).


Thanks, we hope it works as impressive as it looks



Huub3 said:


> I have two questions:
> - the way you have build the pack, are these orange parts, and the mounted buss bars not blocking the mounting of the fourth row?
> - in your opinion, can these batteries be mounted on the buss bars alone, so without these orange parts?


I would not attempt to build a battery out of thes cells without some form of support of the cells bodies. I feel a bit uneasy as it is with only one end supported. The positive end of the cell is made of pretty thin metal that has been releived with lots of holes to allow venting if the burst disc lets loose. It's really flimsey, very easy to bend. 

We chose this method of mounting because it gave us the most compact layout. The orange blocks are Headway's own design. They clip together but not very strongly. Except for the space limits we had I would not use these blocks again in a large battery like this. I would use something like what JackBauer did. The Headway blocks allow just enough room, so they give the most compact format.

You spotted the real problem with this design. In order to replace or install any cell, the battery needs to be disassembled. The 4th row will not be added until next year (death and taxes willing) so we will disassemble and measure and replace as necessary when that happens.



Huub3 said:


> I have an idea for a mounting principle, in which simple parts and some cut metal and plastic can make a solid battery case, with all the wiring integrated. However, this idea builds on the fact that the batteries are mounted at their ends, e.g. the buss bars.


Draw up a reresentation of your idea and post it. Let us all look it over, maybe we can help you develope it.


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## T1 Terry (Jan 29, 2011)

> With this setup it is impossible to overcharge a battery and each full charge bring all cells into balance. When all batteries are stable and at the same voltage, charging is complete. We haven't tried yet but it looks like we can just keep a 48 volt source connected and the batteries should stay perfectly balanced. We'll see . . .


I don't want to pour water on a great parade but I wouldn't want to see your hard earned $$ wasted either. Best you check with Headway regarding float voltages, I believe many of the other larger cells have a 3.4v float because the cells will continue to trickle charge and the casing expands seriously reducing their capacity. Problem is I've read so much about LiFeP04 batteries over the last 6 weeks I can't remember exactly where I read it but I know I read it more than once and there was a case of battery failure quoted that had been attributed to float over voltage.
The safest system appears to be an auto disconnect at 3.55v with a hysterisis of 0.3v to .5v before reconnection for long term storage.

I like both your charging set ups, wish we could get bits that cheap over here. Very hard to buy stuff out of the US, many sellers won't even respond to an email.

T1 Terry


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## galeson (Oct 25, 2009)

Hi Jiim,

I have purchased some synqor converters and have been following your progress. I was wondering if your problem with supplying too much current to the batteries was because you were using a lead acid pack to supply the 48V. Also, what did you do to limit the current?
I like your small boards. Can't wait until you get the last of your problems cleared up.

Galeson


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## Jimdear2 (Oct 12, 2008)

Galeson,

We have done a few mods to the charger boards and have them working quite well. They take in anything between 36 and 72 volts and produce a very stable 3.500 volts.

Actually the problem with too much current would occure with a regulated power supply or 48 volt charger or batteries. It's just that the Headway
batteries have such low IR that you can push everything the SynQor boards can put out into the battery. Caused so much heat that one SynQor board cooked itself. Lack of sufficient cooling.

The final fix was to put a resistance in the output from the SynQor to the batteries. I had originally put 10 gauge from the SynQor to the connector to the parallel buss. What we did to correct this was we took a 24 inch long piece of 16 guage magnet wire, wound it into a coil and inserted it between the SynQor and the battery Parallel Buss, this dropped the current and voltage into the batteries. The coil radiated the heat produced and everything works well. We will be adding fan cooling to the battery case. 

I'm really not electrically compentent so Darin would have to give you the technical reasons this works. He tells me as a side benifit that the charging curve is also much better with the resistor.

We wll be doing the final assembly on the battery this weekend end. I'll take a few pictures of the boards and assembly process and post them up next week.

We (Darin mostly) have done a lot of charging using a single string of 5 charging boards on 5 parallel stacks of 3 batteries. The setup works great.

We have each chrging board adjusted to produce 3.500 volts for its 3 batteries from an input that can vary quite a bit, although we try to keep it around 48 volts. One side benifit is that each board pushes each 3 cell stack to 3.5 volts at its own pace. Top balances the pack each time. Since we will probably never take the battery below a 50% SOC it should never be a problem. 

We also have a Low Voltage Warning and Cut Off that should keep us safe. It's part of the Cell Log monitoring system

I'll also be reporting on how we tested and matched the cells (Kind Of) and some battery FUBARS that we had.

Jim


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## galeson (Oct 25, 2009)

Hi Jim,

Thanks for the information.
In a thread from the endless sphere titled "15S LiPo charger using DC/DC converters" by Jeremy Harris he solved the overcurrent problem with a couple of resistors. I'm wondering if you considered this solution and why you chose the coils instead. He also has fan cooling and it seems to work well.
I can't wait to see your finished pack.

Galeson


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## rwaudio (May 22, 2008)

galeson said:


> Hi Jim,
> 
> Thanks for the information.
> In a thread from the endless sphere titled "15S LiPo charger using DC/DC converters" by Jeremy Harris he solved the overcurrent problem with a couple of resistors. I'm wondering if you considered this solution and why you chose the coils instead. He also has fan cooling and it seems to work well.
> ...


I'm going to play with a slightly different approach to the over current problem by creating a 2 stage charge by switching the voltage trim resistor (or disconnecting it and letting the converter default to 3.3v) then when the current drops to an acceptable level bump the voltage to 3.5v and let the system finish.

I've finally been playing with some discharges, and Jim you may want to play around a little bit if possible with cell temperature and preload the cells to heat them up before a run. I didn't record temperatures, however the cells were still cool enough to hold on to. But with a 125A load on my 10AH cells it would normally stabilize at 2.66-2.7v, however at a certain temperature the cell put out 130A and maintained about 2.9V for a good 15 seconds. It's nothing new that the cells put out more power when hot, but if you mount some big power resistors to the tractor and load them for a certain amount of time before the run, then let them recover you might be able to get just the right cell temperature to make consistent huge power.


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## Jimdear2 (Oct 12, 2008)

galeson said:


> Hi Jim,
> 
> Thanks for the information.
> In a thread from the endless sphere titled "15S LiPo charger using DC/DC converters" by Jeremy Harris he solved the overcurrent problem with a couple of resistors. I'm wondering if you considered this solution and why you chose the coils instead. He also has fan cooling and it seems to work well.
> ...


We did consider resistors but went with the wire coil resistance because of cost, and the coils ability to shed heat.

As many problems as we have had I can't wait to see it complete myself.

Jim


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## Jimdear2 (Oct 12, 2008)

rwaudio said:


> I'm going to play with a slightly different approach to the over current problem by creating a 2 stage charge by switching the voltage trim resistor (or disconnecting it and letting the converter default to 3.3v) then when the current drops to an acceptable level bump the voltage to 3.5v and let the system finish.


RWaudio,

We also thought of that but IMHO that's just one more point for failure. The resistance coil does the same thing and is a lot simpler and probably much cheaper. Your battery with around 500 cells is going to be complex enough with out adding to it.

You should check out this thread in Endless Sphere "15S Li Po charger using DC/DC converters" that galeson points out. The poster has encountered a lot of the concerns we are running into and has some valid pointers.



rwaudio said:


> I've finally been playing with some discharges, and Jim you may want to play around a little bit if possible with cell temperature and preload the cells to heat them up before a run. I didn't record temperatures, however the cells were still cool enough to hold on to. But with a 125A load on my 10AH cells it would normally stabilize at 2.66-2.7v, however at a certain temperature the cell put out 130A and maintained about 2.9V for a good 15 seconds. It's nothing new that the cells put out more power when hot, but if you mount some big power resistors to the tractor and load them for a certain amount of time before the run, then let them recover you might be able to get just the right cell temperature to make consistent huge power.


We have noted that ourselves and were starting to think of some ways to heat up the battery at the track. We were seeing much better performance as the batteries heated up. I had been looking at hot air and other things like driving it around for a while. The resistor pack is a good idea. I believe Darin has enough bus braking resistors to get the job done. I also know where to get some more if needed.

It seems that they really start to perform around 100 degrees F. We will have to do some experiments with the 38120P 8ah cells we have to see where the best performance happens. We are going to plant some thermocouples in the center of the pack as we finish the build this weekend. That may help us get a handle on it.

We could cycle them with a load then charge just before the hook. Just might be the thing.


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## rwaudio (May 22, 2008)

Jimdear2 said:


> RWaudio,
> 
> We also thought of that but IMHO that's just one more point for failure. The resistance coil does the same thing and is a lot simpler and probably much cheaper. Your battery with around 500 cells is going to be complex enough with out adding to it.
> 
> You should check out this thread in Endless Sphere "15S Li Po charger using DC/DC converters" that galeson points out. The poster has encountered a lot of the concerns we are running into and has some valid pointers.


I checked out the thread, some good info. The other consideration for me is that when I plug into 120v outlets I need to keep the total current draw within the limits of a 15A circuit, basically one (of six) of my battery boxes could max out a 15A circuit. I need to be able to tweak the current draw when it starts up to get just the right amount of draw. If I used the resistor method to limit my draw then the remaining 75% of my charge cycle would be at very low power and take much longer than necessary.
Just like the graphs posted at the beginning of that thread showing the difference between 0.1ohm and 0.05ohm resistors.

I also need the flexibility to tweak my draw at 240v, or more likely go to full power much quicker. Since I'm designing a PCB for my setup adding one DPDT relay for every 2 converters is nothing. I would rather design it in, then not use it, then have to redesign it because I can't charge from a normal plug or something. I think I will also allow the provision of adding a resistor to the output if that just happens to be the only method that really works. Or perhaps a combination of the two methods. 



Jimdear2 said:


> We have noted that ourselves and were starting to think of some ways to heat up the battery at the track. We were seeing much better performance as the batteries heated up. I had been looking at hot air and other things like driving it around for a while. The resistor pack is a good idea. I believe Darin has enough bus braking resistors to get the job done. I also know where to get some more if needed.
> 
> It seems that they really start to perform around 100 degrees F. We will have to do some experiments with the 38120P 8ah cells we have to see where the best performance happens. We are going to plant some thermocouples in the center of the pack as we finish the build this weekend. That may help us get a handle on it.
> 
> We could cycle them with a load then charge just before the hook. Just might be the thing.


You could even make a massive "headlight" load with a whole bunch of series/parallel H4 bulbs or something and create a spotlight that shines at the sky. Make it part of your setup to give the spectators something to look at right before you make a pull.


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## Jimdear2 (Oct 12, 2008)

rwaudio said:


> I checked out the thread, some good info. The other consideration for me is that when I plug into 120v outlets I need to keep the total current draw within the limits of a 15A circuit, basically one (of six) of my battery boxes could max out a 15A circuit. I need to be able to tweak the current draw when it starts up to get just the right amount of draw. If I used the resistor method to limit my draw then the remaining 75% of my charge cycle would be at very low power and take much longer than necessary.
> Just like the graphs posted at the beginning of that thread showing the difference between 0.1ohm and 0.05ohm resistors.
> 
> I also need the flexibility to tweak my draw at 240v, or more likely go to full power much quicker. Since I'm designing a PCB for my setup adding one DPDT relay for every 2 converters is nothing. I would rather design it in, then not use it, then have to redesign it because I can't charge from a normal plug or something. I think I will also allow the provision of adding a resistor to the output if that just happens to be the only method that really works. Or perhaps a combination of the two methods.


Are your boards going to be directly at the batteries like ours, or remote?

If they will be remote, at 3.X volts won't you get a quite a resistance in the leads from the boards to the batteries. That is, unless you use something like 10 AWG wire. Plus with a lot of different lengths won't the charge time for the battery sets will vary quite a lot? I believe that was mentioned in that endless sphere thread.

Of course the basic design of our two setups is different, ours is for competition yours is for transportation. You need charge anywhere ability, we will always have our charging station with us. We are going to use a 6500 watt generator running a 240 volt to 48 volt power supply and a BIG battery dump pack in parallel to charge ours, so input current shouldn't be a concern. 

One thing I have been thinking about for version two of our boards is a voltage sensitive ON / OFF control circuit so that when the battery reaches the maximum set voltage it turns that charger board off making more current available for the remaining batteries. Any thoughts?

Something that I think you mentioned and we never checked is drain back through the boards. The way we have it now is when you remove the 48 volt source the board is shut off. Is there still a drain? Wonder if a diode in the circuit wouldn't help? That would also put a measurable resistance in the 3.X volt circuit to the battery, HMMM . . . I'll have to ask Darin to see what he thinks. 



rwaudio said:


> You could even make a massive "headlight" load with a whole bunch of series/parallel H4 bulbs or something and create a spotlight that shines at the sky. Make it part of your setup to give the spectators something to look at right before you make a pull.


Maybe a laser light show for night pulls and a LED show during the day. 

Put a big LED monitor panel above the roll bar and put on a splash show with BIG music. 

Lordy, Lordy could we have fun with that

Jim


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## rwaudio (May 22, 2008)

Jimdear2 said:


> Are your boards going to be directly at the batteries like ours, or remote?
> 
> If they will be remote, at 3.X volts won't you get a quite a resistance in the leads from the boards to the batteries. That is, unless you use something like 10 AWG wire. Plus with a lot of different lengths won't the charge time for the battery sets will vary quite a lot? I believe that was mentioned in that endless sphere thread.
> 
> ...


LOL, go for the light show!

My boards will be close to the cells, I will have 16dc/dc converters on a board, but it will be mounted on top of the pack of 16 series cells, so wires would be about 6" give or take. 

As for the shut off, I've been planning to do a battery bank by battery bank shut off, so when a group of 16S8P cells drops to a certain current draw it will terminate charging to that group, this is mainly so that towards the end of the charge cycle I have available wall power for heating the car and or batteries, even if it's just long enough to preheat my coolant so I can just maintain heat on battery power.

There is a draw on the battery side when you remove 48v power from the converters, however for me it should be minimal since the car will be charged 1-2 times a day. If you store the tractor for long periods of time you may want to find a way to disconnect it... or just remember to charge once a month or so.

You could use a diode, but then you would need to move the sense wire to the battery side of the diode, and I'm not sure if the converter has enough voltage to overcome the diode drop and get up to the 3.5+ volts you need. In that case you might need a 5v converter and trim down.


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## DavidDymaxion (Dec 1, 2008)

What about high speed charging to help keep them warm?


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## Jimdear2 (Oct 12, 2008)

DavidDymaxion said:


> What about high speed charging to help keep them warm?


David,

The power supply/charger we are planning (still have to test it to see if it works) is a 48 volt Lester charger hooked in parallel to four 72 amp hour AGM 12 volt batteries with a pre charge resistor and a contactor. Plug in the anderson to the on board charger's buss and the precharge slowly charges up all of the boards. When the charger buss is up to voltage we close the contactor and dump the batteries into the loop. The limiting resistor we mounted on each board will keep thing sane (we hope), As I say we still have to prove it out.

Jim


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## Jimdear2 (Oct 12, 2008)

We have finally got the battery assembled and mounted and strapped into the tray. 

*WHOOPEE!!!* third time was the charm.

The battery is in a 3P/50S configuration with space provided for a 4P/50S layout. that is 175 volts and 24ah now and 32 ah when we add the 4th layer next year. At a rated 25C we should get quite a kick out of it. 

Physically it is 32 inches long, 16.5 inches wide, 10 inches high and weighs in the area of 110 pounds.

We have cut the lexan end panels and are starting to mount the 48 volt buss for the chargers. The buss consists of two pieces of 1x1x1/8 aluminium angle, one mounted to each end cover. The input buss wiring for the chargers will be positive to one end and negative to the other. We will use an Anderson connector with 8 awg wiring to connect the charger to the respective ends.

You can see from the photos that we have started the buss to board wiring. 10awg wiring to the boards with spade connectors.

The wiring for the Cell Logs will be routed in a similar fashion and will connect to the screw posts on each board.

I'll be bringing the tractor to Darin's next week end for trial fitting the battery. More photos then. 

We sure are glad that all of the troubles with the cells seem to be behind us.


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## Jimdear2 (Oct 12, 2008)

*HooRay*

*Whoopie *

*Sigh of relief*

We finished the assembly and wiring of the individual charger boards and gave it its first test as a complete assembly. I even have the Cell Log wiring on the pack. All 51 wires are tapped into the charger boards. I used a 68 pin scsi cable that had 26 awg wire in it. We just need to make the top cover and attach the most positive and negative cables that will route to the 800 amp breaker.

Guess what? It WORKS ! ! ! It even looks good !

We hooked up a 48 volt set of 32 amp hour (two 16s in parallel) Hawker batteries to the 48 volt buss as a dump pack and powered it up. The charger board are set to 3.5 volt output and the resistor coils limit the current to the batteries to about 3 to 5 amps per cell stack, depending on the cell voltage.

The parallel cell stack voltages were all over the place from initial testing. They varied from 3.2xx to3.34x. The resistor coils we added to the charger boards kept the current to a reasonable limit, about 30 amps in the 48 volt buss. The charger boards kept the current steady as the cell voltages started to rise. We then added a 48 volt battery charger to the battery pack to keep the dump pack somewhat stable.

When the the cell voltages started to cross 3.40x volts the current had moderated on the higher voltage cells while the lower voltage cells were still getting higher charging currents. At about 3.450 volts, all of the cells had pretty much matched. I had to leave at that point. Darin will allow the cells to reach 3.5 volts and then shut down the charger and let the pack normalize. 

Darin thinks it will settle at 3.35 to 3.36 volts. I'm hoping for closer to 3.40 volts. I guess I'll find out when he emails me tomorrow.

We are going to set the battery in the tractor Tuesday night to fit up the mount points and seat mounts.

Photos and more info later.
Jim


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## rwaudio (May 22, 2008)

Jimdear2 said:


> *HooRay*
> 
> *Woopie *
> 
> ...


Congrats Jim, that's a big step!! I'm glad to hear everything is working as planned. I can't wait to see what that tractor can do. Looking forward to the first video.


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## Woodsmith (Jun 5, 2008)

Fantastic stuff Jim, I've been lurking mostly, on this thread as it is over my head at the moment but it is great that the charging system works and the pack is together.

When are you hoping to test it on the tractor?


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## Jimdear2 (Oct 12, 2008)

Rw,
Woody,

We had the first NICE day this year so I've been outside all day cleaning up and airing out. I also have felt better once I got outside in the sunshine. Breathing easier even though the humidity was a bit high.

Thanks for the support. Both of you have been a big help when I stated to doubt the path I was on.

We should set the battery into the frame on Tuesday night. 

I will take a camera.

Once we get the battery tie downs done we can locate, route and measure all of the other stuff. With Easter and other stuff coming up, Darin will have a lot of family stuff to do, Things will slow down a bit until May so I can take the measurements over to the machine shop and get some stuff done. I can work on the steering of the ICE tractor.

Getin it dun!!!

Jim


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## Jimdear2 (Oct 12, 2008)

Hi all,

A quick update and a couple of pictures of the assembled battery. 

First picture is a shot down the length from the front. It shows the Anderson plug and fuse holder for the 48 volt buss. It also shows the scsi cable gender changer screwed to the front cover with the cable from the cells plugged in. 

The cable from the cell logs is under construction. When completed the cable will run from the white plastic board shown on the front of the tractor, that will have the seven cell log 8Ms mounted. Each battery stack will be monitored for voltage and set up with a LVC and alarm. The LVC will shut down the tractor if it sees 2 volts or less. A visual check of the condition while charging will tell us how each charger board and cell stack is doing.

The remaining pictures show a look at the top of the battery with the charger boards, the 48 volt buss cables and the 50 individual connection wires from the cell logs.

The last picture is the battery from the rear. (I don't know what the red smears are) there will be two 4 inch muffin fans and of course the power cables.

We hope to set the battery into the frame tomorrow night to fit it up and make any mounts needed. We are going to Lowes to pick up the lexan for the cover first so that may slow us down.

All of the remaining materials should be arriving this week as well.

We ran a test charge on the battery, all of the cell stacks were charged to the charger boards preset voltage of 3.5 volts. Since cells were all at a different SOC due to handling and testing they all arrived at 3.5 kind of staggered time-wise. But they all did reach 3.5 volts. Now after normalizing the cells all read 3.37 to 3.38. The cell stacks have sat for about 3 days so the stacks should be well balanced.

Looks like it's going to be a winner.

Jim


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## Woodsmith (Jun 5, 2008)

That looks fantastic, Jim!

It also looks complicated.

Seems like your charging system is working as expected. I will have to read back and study the detail.


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## rwaudio (May 22, 2008)

Hi Jim,

Everything looks great, well done!

Isn't it nice when you don't have to worry about SOC when you assemble the pack? This is probably less of a problem when dealing with 45 100ah cells, but the 150 in your tractor or the 768 that would go in my car (if I go that route, still waiting for the A123 to arrive) would make it very difficult to make sure all cells are balanced.

I'm looking forward to hearing about your first run, or test runs.


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## Jimdear2 (Oct 12, 2008)

To all,

Thanks for the encouragement and support. We moved the battery to the frame tonight, again no camera, maybe pictures on Friday

Once the charging/monitoring system is done it will be wonderful to just look at pack voltage on the main voltmeter then glance over the cell logs to look for problems or see the pogression of the charge. Just knowing that our system cannot overvolt a cell. Something which can happen with a gang charging system, even with a shunting system.

I've been working on the cell log wiring. the half on the battery was easy. The half for the cell logs is . . . shall we say difficult. The big difficulty so far is the appearance of the color codes marking on the wire change with natural, floresent, LED or incandecent lighting. Plus it looks like I might have gotten some of the pairs mixed i.e. I wrote down blue with white instead of white with blue. Well just have to fight it till I win.

Tomorrow is another day,
Jim


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## Jimdear2 (Oct 12, 2008)

Hi all you pulling tractor fans.

We did "JUST" get the battery in the tractor last night. We first ,had to make up a lifting strap and of course it had to be made of non conductive stuff. and we had gone to the big box store to get some Lexan to make a cover so it was late when we set it in the frame Going back to work on it again Friday night . . . Maybe. 

If I do go, Ill get pictures.

Another milestone Has past, Got the cell log monitoring system wired to the mounting board. Man 51 26 AWG wires by color code to 7 plugs to 7 cell logs. I now know why Major wants so much to make up those plugs. Tiny little things, not good for old eyes and shaky hands. Took 90 pins to make up the 51 connections, glad we ordered 100.

Got lucky with the special, tool, Darin had one he didn't even know about. He stumbled across it just before I was going to eBay a tool for 200.00.

The picture shows only six cell logs, unfortunately Darin had an OOPS moment with one of the ones we had on hand and let the magic smoke out. Surprised me, that's usually my job. Of course since I didn't order in a spare, they are now on back order. Just have to wait until some come in I'm 8th on the list waiting.

The layout of the units is kind of straggly because I need to anchor them better. Right now there is a piece of rolled masking tape under them. Once we circuit test the harness, we can plug in them in and will have a cool way to monitor charging and condition. I'm going to use one of the spare pairs in he scsi harness to add a 200V digital voltmeter that I have extra, so we can watch that as the battery charges and get a quick estimate of SOC.

Need to bend up the battery cover lexan so we know where to mount the seat and circuit breaker now that the battery is in.

I just received the 10 x 18 inch piece of heat sink the will be mounted above the motor and will have the controller, (P&S for now, until Darin's is finished.) contactors, reversing contactor, and other stuff. A quick test drive with Video Of Course.

Once that's done we strip it, paint it, assemble it and PULL.

Jim


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## Frank (Dec 6, 2008)

Nice work Jim. It's been awhile since I've visited this thread but I've learned something about the Cell logs you may or may not know about. I have the 8S's and if the 8M's are powered the same way, they can drain your batteries unevenly. The cell logs take power from the first six batteries they're hooked to and don't draw from 7 or 8. I use TS100AHA's in a motorcycle project that only looked to be down 6-7 AH over the winter (per my Cycle Analyst, pretty much the way I left everything) but in reality some were down 30-40 AH each!

The current shunt doesn't measure losses to power the Cell Logs as they're hooked directly (and it's a very small power draw in any case) but I found cells 7,8 to be down ~10-15 AH and the other 6 to be down a whole lot more. Your charging setup should take care of this problem but be careful about letting the cells sit more than a couple of months w/o charging if you leave the cell logs hooked up. I guess your other boards might exacerbate the issue as well. Better safe than sorry!

There is a modification that (supposedly) works to even out the power draw. I've made it but don't know if it's been successful yet. I'm in the process of top charging my cells to even them out then will see.


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## Jimdear2 (Oct 12, 2008)

Frank said:


> Nice work Jim. It's been awhile since I've visited this thread but I've learned something about the Cell logs you may or may not know about. I have the 8S's and if the 8M's are powered the same way, they can drain your batteries unevenly. The cell logs take power from the first six batteries they're hooked to and don't draw from 7 or 8. I use TS100AHA's in a motorcycle project that only looked to be down 6-7 AH over the winter (per my Cycle Analyst, pretty much the way I left everything) but in reality some were down 30-40 AH each!
> 
> The current shunt doesn't measure losses to power the Cell Logs as they're hooked directly (and it's a very small power draw in any case) but I found cells 7,8 to be down ~10-15 AH and the other 6 to be down a whole lot more. Your charging setup should take care of this problem but be careful about letting the cells sit more than a couple of months w/o charging if you leave the cell logs hooked up. I guess your other boards might exacerbate the issue as well. Better safe than sorry!.


Frank,

Thanks for the heads up. Darin and I are really happy with the results so far. If it goes as good as it is starting to look . . Watch Out.

Yes we were aware of the draw down. We figured that for long term storage we would just disconnect the scsi cable at the connector. Short term (one to two weeks) we are discussing leaving the charger on, regular (TBD) top up charging or installing shut down relays on the jumpers between units.



Frank said:


> There is a modification that (supposedly) works to even out the power draw. I've made it but don't know if it's been successful yet. I'm in the process of top charging my cells to even them out then will see.


If you could please post a link to this modification and also post the results of the installation.

Thanks,
Jim


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## Frank (Dec 6, 2008)

Jim -

Link to a link: http://endless-sphere.com/forums/vi...&p=377170&hilit=cell+log+modification#p377170

HTH


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## Jimdear2 (Oct 12, 2008)

Frank said:


> Jim -
> 
> Link to a link: http://endless-sphere.com/forums/vi...&p=377170&hilit=cell+log+modification#p377170
> 
> HTH


Frank,

Thank you, The electronic half of our partnership will follow up on the link. 

Electrons mike my eyes glaze over.

Jim


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## Jimdear2 (Oct 12, 2008)

As i said earlier, the battery was in the tractor. 

First thing we did was prove the cabling from the charger boards to the cell logs. only two mixed pairs Yellow/Brown-Brown/Yellow and Yellow/Tan-Tan Yellow. Not bad for these old eyes and shaky hands.

Plugged in the cell logs and found one DOA. so with the one that the magic smoke was let out of and the DOA we are two short. I ordered three more but they are on back order (of course)

We then completed securing the battery to the frame and decided to make up a polycarbonate (Lexan) cover to go over the batteries. WELLLLLLLL, I'll tell you bending Lexan with a heat gun is not as easy as it looks in the YouTube videos. 

It's a good thing we can salvage most of the material for the boxes and enclosures for the circuit breakers, contactors, controller and such. Going to glue that stuff. I ordered a professionally made cover that will be stronger(thicker) and almost as cheap as the material that we tried to bend.

Two lessons here. If you plan to bend this stuff, get a bender. If you need covers and boxes, go to a professional first and get a quote.

Once we had the battery secure and cover dimensions we started on the seat supports. They are steel hoops that go over the battery and are clamped to the frame the seat is bolted to tabs. Loosen four hose clamps and a wire connection and the seat lifts off to access the battery.

With the seat in place we could fabricate the mount for the circuit breaker (a real monster, 800 amps about 15 pounds) Nice thing about the breaker is it is also the emergency disconnect. We will use a Big Red Button to send a 24 volt pulse to the breaker, this trips it open. There will be a small battery and/or capacitor to supply the needed voltage.

The breaker internally uses a shunt to sense current, that shunt generates a voltage signal when when current flow exceeds the rating which will trip the breaker.

For the tether switch and the LVC we will interrupt the contactor circuit.

You will notice in the photos there is a heat sink laying on top of the motor. It will be mounted approximately here about 1 inch above the motor. All of the controller, contactor and electric/electronics will be mounted on the heat sink and enclosed in a lexan box.

This pretty much concluded battery assembly. We will continue to post specifications and test results here, but for the remainder of the build we will go back to the construction forum.

Jim


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## Woodsmith (Jun 5, 2008)

Looks good, Jim, Just need a coat of paint on that chassis frame.

That is a chunky looking breaker.


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## JRP3 (Mar 7, 2008)

Very impressive work.


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## Jimdear2 (Oct 12, 2008)

Woodsmith said:


> Looks good, Jim, Just need a coat of paint on that chassis frame.


Paint comes after we are done welding on the frame. Still need to do the roll bar and a couple of brackets and such. Then a LOT of sanding, some wire brush work and a lot of rust reformer primer. Thinking of gloss or simi gloss black for the frame. Electric Blue (like the motor) for the fenders and hood. 



Woodsmith said:


> That is a chunky looking breaker.


Yep it is a big sucker. It weighs in around 15 pounds I believe. There are 4 200 amp airpack breakers in parallel, with a shunt across the back of all of them and the trip mechanism. Throw more then 800 amps across the shunt and the voltage generated will trip the breaker mechanism. What is nice is the trip has external points that allow remote trip.

The neat thing is I got them for around 40.00 each (I bought 2) New they retail for $1400.00. Even better I can still access the data sheet.

Back to it, need to get it and the yellow tractor done. We have been invited to a parking lot show in mid May for the employees of the St. Clair Detroit Edison Power Plant. Should be fun.

Jim


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## Jimdear2 (Oct 12, 2008)

JRP3 said:


> Very impressive work.


JRP3, 

Thanks, I needed that encouragement.

My back is killing me (LOL).

Jim


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## rwaudio (May 22, 2008)

Very nice work Jim, the tractor has come a long way!

I wish I was that far with my build.


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## ruckus (Apr 15, 2009)

Please tell me you have a cover for that chain and that you would never run it exposed like that. ~:q 

I see chains like that fail all the time on the farm.


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## Jimdear2 (Oct 12, 2008)

ruckus said:


> Please tell me you have a cover for that chain and that you would never run it exposed like that. ~:q
> 
> I see chains like that fail all the time on the farm.


Thanks for the warning, we most definitely have guard, it's 3/16 steel.

I just have it off to give a little more room and make up a new tensioner. We rushed it together last fall to make a trial run with half the voltage (very disappointing because I sill had the 170 volt gearing in it).


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## 1-ev.com (Nov 4, 2010)

Hey Jim,

How the "Revolt" controller is doing? I have one for my Customer, he wanted, so I want to collect more info before my testing on the car. I did bench testing, but it no match for real TEST. 

I have similar heat sink too, but I want to mount controller upside down, or/and put fan...

Have you drill holes into the sink to accommodate bolts/nuts on the bottom that are sticking out?

http://1-ev.blogspot.com/2010/10/starting-project.html 

Also, for this MOTOR you may need "Soliton1" or "Zilla" or similar... 

Thank you.
-Youri.


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## Jimdear2 (Oct 12, 2008)

1-ev.com said:


> Hey Jim,
> 
> How the "Revolt" controller is doing? I have one for my Customer, he wanted, so I want to collect more info before my testing on the car. I did bench testing, but it no match for real TEST.


We haven't run the ReVolt on the tractor yet. It was built to run a different tractor but we haven't finished the BIG 13 controller so the ReVolt is being pressed into service for now.



1-ev.com said:


> I have similar heat sink too, but I want to mount controller upside down, or/and put fan...
> 
> Have you drill holes into the sink to accommodate bolts/nuts on the bottom that are sticking out?


We will drill and tap as necessary, since the tractor will run under a heavy load for only a few seconds thermal mass is more important. We will most likely use a fan but mount the controller upright.



1-ev.com said:


> Also, for this MOTOR you may need "Soliton1" or "Zilla" or similar...
> 
> Thank you.
> -Youri.


We are going to try building a simple 1000 amp controller ourselves. Remember this needs to run under heavy load for only 15 seconds or so. The 3+ thousand would be better spent on a bigger battery.

Thanks for your comments,
Jim


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## 1-ev.com (Nov 4, 2010)

Thank you, Jim


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## Jimdear2 (Oct 12, 2008)

Hi all,

Been kind of remiss on my posting.

Have a few things to report on the battery/charging/monitoring system, some very good a few kind of bad.

The good stuff first. 
It works fantastic (when it all is functioning . . . more on that later)

It top balances the cells flawlessly and does so in a timely manner. 

Our charger design, 4 deep cycle batteries and a 48 volt charger, does a fine job. The whole setup is mounted on a small cart with a small generator. We can charge the battery anywhere. Add a 4 panel solar array and we could charge all week and claim the tractor was solar powered.

With the cell log 8m units working and set to display the bar graph, we can see the SOC at a glance. The LVC system works as follows, when any battery stack drops below a set point, it triggers a relay that will either shut down the tractor completely or go to 75% power (we haven't decided yet which would be best). 

The cell log units allow you to check your pack balance at any SOC. During charging you can see which cell stacks may have a problem and also know when the pack is fully charged. You can see instantly if there is a problem.

THIS WORKS!!!

In our case we saw that a couple of battery stacks had discharged to less then one volt. That is when we discovered the moisture damage. Another plus to our design is when we need to re balance the charge of one stack it is simple to disconnect that one board from the 48 volt buss (pull spade connectors) and connect to a 48 volt supply and charge a single battery stack. This allowed us to bring the packs we found under 1 volt back up and cycle them a few times to the point that they now will charge up to 3.5 volts and relax down to 3.35 like the rest of the stack. 

Right now we are top balancing by allowing all of the parallel stacks to reach 3.5 volts. 

If we wanted to go to a bottom balance strategy we would simply discharge all of the cell stacks to say 2.2 volts then connect up the charging boards and charge until a set desired voltage in the cell logs was reached and use that alarm event to shut off the charger.

I still think that this type system, if properly developed, would be superior to any other type charger/monitoring system, especially for prismatic. 

Now the (not so) bad stuff

Made some poor choices on wiring up the cell logs and will have to redo the wiring this winter.

Now the real stinger:
The Syn Qor DC to DC units we chose are incredibly sensitive to condensation moisture. The surface mount components on the board are so closely packed together that any moisture at all will bridge between leads of the chips and cause magic smoke. We have burned out 15 boards and I'm down to my last spare. 

If I can't find a solution, it looks like we will have to replace all 50 boards with something else. I'm going to try some spray on electrical varnish to see if I can't moisture proof the Syn Qor boards. Also I have found a couple of similar boards that claim to be moisture resistant but they are quite expensive.

I have found and ordered samples of 4 different mfg's. boards with the same physical size and similar specifications. If the weather proofing of the Syn Qor boards does not work I will have something to test out for replacement.

Any suggestions about weather proofing would be welcome.

All in all I would say that this charging monitoring setup is a good way to get a very stable (other then the moisture problem) light weight, on board charging/monitoring system that can use any charger from 36 to 72 volts.


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