# Sky Energy vs ThunderSky testing (EV Components)



## EVComponents (Apr 20, 2009)

We have been getting a lot of questions about the differences between ThunderSky and Sky Energy cells. 
So now that the first two containers have been ground shipped and everyone will soon have their cells, we have time to do our testing. 

We have purchased a CBAII with two 1000 watt amplifiers. We are going to test each cell as much as our equipment will allow, up to 3C. 

We plan to document SE vs TS cells in the following head to head matchups. 

SE 40 AH vs TS 40 AH 
SE 60 AH vs TS 60 AH 
SE 100 AH vs TS 100 AH 
SE 180 AH vs TS 180 AH 

They each have other cell sizes, but those are the sizes that have the same numbers. 

In the first preliminary results, the TS 180 AH narrowly beat the SE 180 AH. 
The results will be posted once we have more data to share. 

If you have any specific questions you want answered, please let us know. 

Thanks, 
James Morrison 
www.evcomponents.com


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## dimitri (May 16, 2008)

When I bought my TS cells from Elite Power I was told that cells capacity varies from batch to batch, but as long as its more than rated capacity, it passes QC and goes to the customer.

So, for example, many of my 160AH cells have actual capacity of 175AH.

With this in mind, how valid is your testing of 2 cells of different product line of the same rated capacity? Obviously you have no way of controlling actual capacity of 2 cells being compared, you just picked them from the box at hand.

Maybe this time TS beats SE, but pick from another box and its the opposite result.

What is the point of all this testing?

I think the only useful test is to see how much current they can deliver before they suffer some kind of damage, but how can you quantify long term damage of the product that supposed to last 10 years?

just my $0.02


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## EVComponents (Apr 20, 2009)

The purpose of our testing is to generally verify the claims of both TS and SE. There are a lot of questions out there about whether these cells meet expectations.

While we cannot do a 3,000 cycle test, we can provide good data on how they perform compared to each other.

Your example of the ThunderSky cells is a good example. You have the 160 AH and it actually provided 175 AH when new. That is worth knowing. Are they being conservative when they rate their cells? Or are they stretching their claims for the purpose of marketing and competition?

We hope to get a better feel for that by testing a few cells from every batch that comes through our warehouse.
This data gathered over time and from many different batches will enable us to more properly rate the overall products provided by both companies.


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## dimitri (May 16, 2008)

When I asked Elite Power about specific capacity of my cells, they sent me a spreadsheet of every one of my actual cells by serial number and it had specific capacity and internal resistance of each cell. This data did not come from Elite Power, it came from the factory. So, since you buy from the same factory, you should be able to get the same data from China and pinpoint capacity of each cell by its serial number. Do you guys have this data? If so, then random testing of cells should just confirm test data from the factory QC process.

My point of comparing random cells of TS and SE and stating that one is a little better than the other is not a good way to say that one product is better than the other in general. I think these are both great products and equally deserve their marketshare.


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## EVComponents (Apr 20, 2009)

We do receive that same data from the factory. But I am reminded of a famous line in regards to nuclear arms control.

"Trust, but verify." (Ronald Reagan)


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## CroDriver (Jan 8, 2009)

dimitri said:


> I think the only useful test is to see how much current they can deliver before they suffer some kind of damage


That's exactly my point!! 

NO ONE has tested the maximal current the cells can deliver. 

Please guys, sacrifice one cell and make that test 

You don't have to do 3000 cycles, just take a cell and try to put out 10C or 20C and see what happens after 15 seconds


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## EVComponents (Apr 20, 2009)

CroDriver said:


> You don't have to do 3000 cycles, just take a cell and try to put out 10C or 20C and see what happens after 15 seconds


That will require equipment that I don't have. Maybe Rich "Madman" Rudman at Manzanita Micro can do it for me. He likes to blow stuff up.


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## bblocher (Jul 30, 2008)

CroDriver said:


> That's exactly my point!!
> 
> NO ONE has tested the maximal current the cells can deliver.
> 
> ...


I read in one of the TS docs that the 10C rating was in the ms range. So 15 seconds should be the death of it 

I can't imagine it would be good, but it would be nice to know exactly what it does. Maybe it keeps working but capacity was just reduced in half? Maybe the effect is barely noticable? I currently push my 160Ah cells to 3C daily in my commute to work (some damn steep grades). I'd like to up the controller and get some more performance out of the car, but I'm afraid I'd shorten the cell life by exceeding 3C at all. If you could push a cell at 10C for 15 seconds, and it have no noticable affect then I'd feel safe pushing mine to 5C for brief durations on a daily basis.


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## tomofreno (Mar 3, 2009)

> I currently push my 160Ah cells to 3C daily in my commute to work (some damn steep grades)


How long do you keep it at 3C? I have some long grades of about 4-5% around me and wondering how my ev-in-progress might do on them. What % grade do you pull 3C on (I'm familiar with the mass, etc of your car)?

Thanks,
Tom


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## bblocher (Jul 30, 2008)

tomofreno said:


> How long do you keep it at 3C? I have some long grades of about 4-5% around me and wondering how my ev-in-progress might do on them. What % grade do you pull 3C on (I'm familiar with the mass, etc of your car)?
> 
> Thanks,
> Tom


It feels like forever, but it's probably more like 60-90 seconds on the longest ones. I have to shift into 5th of 6 to get enough torque as 4th gear my RPMs will be too high for power. Then I can hold 65mph and even accelerate a little on some of the grades.

None of them are marked. I'd say the longer ones are 4% and all the way up to 6-7% but those are much shorter (about 15 seconds to get up).


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## dimitri (May 16, 2008)

Brian,

how can your Curtis even sustain 3C current on the battery side? I didn't think it could do it for more than few seconds. Are you measuring battery or motor current?

My current Beta revision of Soliton1 is limited to 500 amps continuous, which it delivers without hesitation, so I know I can pull 3C from my 160AH cells for as long as I care to keep the pedal to the floor 

I pull 3C during acceleration on regular basis, for 15-30 seconds at a time, or even longer when getting to 75mph on a freeway.

Soon my Soliton1 will get 1000amp face lift and I will see how much over 3C I can pull


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## bblocher (Jul 30, 2008)

I'm measuring on the pack side. It's not 3C, but close, it will pull well over 400 amps continously on the pack side up those grades.

I have some VERY interesting results from my Curtis and two different kelley controllers that we just did some head to head tests on. I'll be posting all that to my blog soon.


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## JRP3 (Mar 7, 2008)

EVComponents said:


> In the first preliminary results, the TS 180 AH narrowly beat the SE 180 AH.
> The results will be posted once we have more data to share.


Have you noticed any temperature difference between the cells during discharge? Jack Rickard has mentioned a higher temperature on the SE cells.


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## tomofreno (Mar 3, 2009)

> Have you noticed any temperature difference between the cells during discharge?


Temperature is of interest to those of us in cold climates as I understand the cells have to be heated in temperatures below around 30 F in order to take a full charge. Keeping them warm in winter requires insulated boxes, but raises concern with overheating in summer. I would like to know how much heat flow there is from the cells. I was told they remain at ambient temperature during normal operation including freeway driving. Is this in enclosed but uninsulated boxes, open top boxes, open racks...at 1C, 2C...?

It would be nice to have one or more put in an enclosed box with walls of known thermal conductivity and thickness, and temperature versus time measured at 1C or more discharge until temperature reaches equilibrium to estimate the heat flow, Q, from them using the simple one dimensional heat equation (assuming approximately uniform heat flow through all walls). Then one could estimate how much forced convective cooling would be required in summer for a given insulation value in the boxes.

Tom


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## BWH (Sep 26, 2008)

Hey All,

I emailed a friend of mine who used to work in the Exide labs about the Thunder Sky LiFePO4 discharge limits. This was his reply:



> The effect of too high a discharge rate is primarily the creation of excess heat in the batteries. If the batteries are adequately cooled by a methodology such as the liquid cooling employed by Tesla, little damage will occur until the 20C discharge rate is reached. In the case of internal air cooling, battery damage and a possible fire could occur at discharge rates beyond 10C.
> 
> Mike


So it sounds like as with everything else electrical the cooler you keep them the longer you can get peak performance.


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## JRP3 (Mar 7, 2008)

I'm not sure that temperature is the only concern with higher C rates, and if the temperature is too low I don't think they can develop the higher C rates.


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## etischer (Jun 16, 2008)

bblocher said:


> I currently push my 160Ah cells to 3C daily in my commute to work (some damn steep grades). I'd like to up the controller and get some more performance out of the car, but I'm afraid I'd shorten the cell life by exceeding 3C at all. If you could push a cell at 10C for 15 seconds, and it have no noticable affect then I'd feel safe pushing mine to 5C for brief durations on a daily basis.


Some of TS data sheets show a discharge curve for 5c, so you might be safe to up your current. 
http://www.thunder-sky.com/pdf/200871782241.pdf


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## bblocher (Jul 30, 2008)

etischer said:


> Some of TS data sheets show a discharge curve for 5c, so you might be safe to up your current.
> http://www.thunder-sky.com/pdf/200871782241.pdf


Wow, that's new. They did 5C for the entire cycle, impressive. Yeah I'm looking into my options for more power on the controller side.


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## dimitri (May 16, 2008)

This is what I love about ThunderSky, their product gets better and better on paper, while already sitting in my car  , don't even have to upgrade my cells to get better stats 

Joking aside I am glad that TS is continuing to stress their product and discover new limits, so we can enjoy the results.

Soliton1, we are ready for you, bring that 10C on.....


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## dimitri (May 16, 2008)

For those of you up North, does it seem like new temp graphs show that you may not need to insulate your batteries at all or maybe just slightly?

Assuming you charge in the garage at night you should be above freezing in the morning. Then if you park at work all day, you would start with deeper voltage sag, but they will heat themselves up as you go?

Seems that temp range is pretty wide for any reasonable climate.


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## tomofreno (Mar 3, 2009)

I'm just going by what Dave Kois of evcomponents told me: The cells only take about 60% charge at around 30 degree F. My garage is detached and unheated so the cells would be at 10 to 20 F many mornings in winter if unheated. I don't think charging generates much heat, and I was also told by Dave that the cells stay pretty much at ambient temperature during "normal use." What do you find Dimitri? Do the cells heat up during charge, or discharge at say 1C?

Tom


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## el ohmbre (May 28, 2009)

I'm currently running 20 Trojan T-145 lead acid batteries and not happy with the overall performance so I'm just beginning to read about other battery technology.

I think further break in, different tires and better driving techniques will help me but based on the performance you guys are dicussing, I'm getting interested in these SE and TS batteries.

Can someone tell me, what is this "3C" of which you speak?

Tom
www.elohmbre.com


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## dimitri (May 16, 2008)

I do not notice any obvious heatup from the cell's internal resistance. I charge at 20 amps, which is nothing for cells capable of 1C charge current, 20 amp doesn't even break a sweat for them.

As for discharge, its hard to say, I average about 1C with few seconds bursts of 3C during acceleration. When I get home I touch the cells in various places and I can't sense any significant difference from ambiant temp, maybe a couple degrees here and there. Please note my cells are enclosed in a plywood lined box with plexiglas on top, no forced ventilation anywhere. They seem to be doing just fine even in Tampa's 100F heat.

I can't figure out how to calculate heat generated based on voltage drop or internal resistance, I am obviously making a mistake somewhere.

If I see voltage drops of 0.2V per cell at say 400 amp load, does that mean that each cell creates 80 Watts of heat? That seems a bit excessive.

On the other hand, I was told my cells average internal resistance is 0.35 ( I assume this means 0.35 mOhm or 0.00035 Ohm , maybe this is wrong assumption, can someone confirm? ). In this case 400 amp load should only cause 0.14V drop and translate to 56 Watts of heat. 

Considering that 400 amp load only lasts few seconds and average is about 100 amp, then I should see somewhere between 14-20 Watts of heat from each cell, or in my case of 40 cells 560-800 Watts of heat.

I am not sure that I am observing this much heat, but maybe I am just not not measuring right , or maybe it dissipates quickly and doesn't build up the temperature, I don't know.

If someone has more data or experience, please chime in. I'd like to know if I am on the right track here.


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## dimitri (May 16, 2008)

tomofreno said:


> The cells only take about 60% charge at around 30 degree F.
> Tom


This is interesting, does it mean that as long as cells are warm during charge and take 100% charge, then later during discharge when they get below freezing they can still deliver all that charge back to the motor?

I know that Lead Acid loses most of its charge below freezing, but not sure if its similar in LiFePo4 chemistry.

Tom, you could rig a heating element to the charging circuit, so the pack is kept warm during charge from the mains line, this way you don't need to waste pack energy keeping itself warm.


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## dimitri (May 16, 2008)

el ohmbre said:


> Can someone tell me, what is this "3C" of which you speak?
> 
> Tom
> www.elohmbre.com


C stands for amount of current equal to the cell's rated capacity. For example cell rated 100ah can deliver 100 amps for one hour, in this case C=100 amps.

You can safely draw 3C from these cells, obviously for 1/3 of the time. In this example 100ah cell can deliver 300 amps for 20 minutes.

In Lead Acid battery you typically only get half usable energy at 1C rate, but LiFePo4 cells come with real 1 hour rate, you can depend on it.


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## JRP3 (Mar 7, 2008)

dimitri said:


> On the other hand, I was told my cells average internal resistance is 0.35 ( I assume this means 0.35 mOhm or 0.00035 Ohm , maybe this is wrong assumption, can someone confirm? ).


My SE data sheet lists the cells ranging from 0.28-0.34 mOhm, so that sounds correct.


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## dimitri (May 16, 2008)

JRP3 said:


> My SE data sheet lists the cells ranging from 0.28-0.34 mOhm, so that sounds correct.


Interesting, if SE cells have similar internal resistance and exactly the same construction as TS cells, then we have no reasons to expect SE cells to produce any more heat than TS cells at a given discharge current.


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## el ohmbre (May 28, 2009)

Thanks for the response on the "C" rate. I don't want to hijack this thread so I'll start a new one with my basic battery questions.

Tom
www.elohmbre.com


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## JRP3 (Mar 7, 2008)

After spending a little time messing with battery configuration I can say that the SE battery clamping system sucks. The end brackets look like they take up more space than the TS types, and they don't grab the ends as well because of the smaller surface area. The threaded rods on the sides don't fit into the side grooves the way the TS straps appear to so they don't lock into the cells, and if you try to pick up a bunch of cells by the ends they may try to slip out. Also since the rods don't fit into the side grooves they take up more space. From the pics I've seen the TS cells look as if they come pre strapped, with handles, and ready to go, which would make placement experimentation much easier and the final pack able to fit in tighter spaces.


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## 86Honda (Apr 15, 2009)

JRP3 said:


> From the pics I've seen the TS cells look as if they come pre strapped, with handles, and ready to go, which would make placement experimentation much easier and the final pack able to fit in tighter spaces.


They do. They take up almost the same space as my old 12V FLAs - convenient for me. Another thread mentioned waterbed heaters as a good way to heat packs - waterproof, thermostatically controlled, run on regular AC. I may just try that.


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## samborambo (Aug 27, 2008)

dimitri said:


> I do not notice any obvious heatup from the cell's internal resistance. I charge at 20 amps, which is nothing for cells capable of 1C charge current, 20 amp doesn't even break a sweat for them.
> 
> As for discharge, its hard to say, I average about 1C with few seconds bursts of 3C during acceleration. When I get home I touch the cells in various places and I can't sense any significant difference from ambiant temp, maybe a couple degrees here and there. Please note my cells are enclosed in a plywood lined box with plexiglas on top, no forced ventilation anywhere. They seem to be doing just fine even in Tampa's 100F heat.
> 
> ...


56W/cell of heat at 400A. 3.5W/cell at 100A.

Maybe you could replace the BMS shunt resistor with some insulated nichrome wire (heating wire) wrapped around the cell many times. Since the lower charge acceptance means that the cell is hitting its voltage limit too early, the shunt would heat up the cell gently and the cell would start accepting more current (cell voltage would start to drop again). Experimentation would be in order I think.

If you had the MSDS for those sells it would be really easy to work out the temperature rise for the cell when insulated (worst case).


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## Lordwacky (Jan 28, 2009)

samborambo said:


> 56W/cell of heat at 400A. 3.5W/cell at 100A.
> 
> Maybe you could replace the BMS shunt resistor with some insulated nichrome wire (heating wire) wrapped around the cell many times. Since the lower charge acceptance means that the cell is hitting its voltage limit too early, the shunt would heat up the cell gently and the cell would start accepting more current (cell voltage would start to drop again). Experimentation would be in order I think.
> 
> If you had the MSDS for those sells it would be really easy to work out the temperature rise for the cell when insulated (worst case).


I don't think that would work because your BMS shouldn't start shunting until the last "current trickle" stage of charging. You'll want your battery heated during the whole charging phase especially the High current phase. I could be wrong though. 

I'm thinking that some system powered from the mains is the way to go. What about the heat tape that is use to keep water pipes from freezing?


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## EVComponents (Apr 20, 2009)

JRP3 said:


> After spending a little time messing with battery configuration I can say that the SE battery clamping system sucks.


That opinion seems universal. We are talking with Sky Energy about them using the ThunderSky clamping system. Sky Energy used to use it back when they were making cells under contract for ThunderSky. Not sure why they like this new hardware better. Must be cheaper for them.


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## samborambo (Aug 27, 2008)

Lordwacky said:


> I could be wrong though.


*ahem*

Using the BMS shunts to warm the cells not really that much different to running a separate AC heater, except you have a lot more control over cell temperature with the shunts since its self regulating.

What do you think happens to the cell voltage during bulk charge CC phase in cold conditions? The cell voltage increases. The voltage will reach the shunt threshold very quickly and cause the shunt to heat the cell. At the same time, the shunt will limit current through the cell, stopping it from increasing in voltage. As the cell heats up it will start accepting more current. The increased IxIxR losses will keep the battery warm until the CV phase is reached. 

The charger and BMS may need to be a little smarter to stop the charger entering CV mode too soon.


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## dimitri (May 16, 2008)

samborambo said:


> The charger and BMS may need to be a little smarter to stop the charger entering CV mode too soon.


Sam,

while the overall idea is solid, the above quote is the killer. I think most DIY people try to manage cost and complexity, and finding a smart reasonably inexpensive charger is a tall order.

Typical shunt current is less than 2 amps and you don't want to start shunting during CC phase, it will overrun shunts in an instant. Once charger reached CV phase they don't usually go back to CC phase, so the charging process will stretch for many hours.

Assuming 2 amp shunting ( you could redesign whole BMS to increase it, but its such a hassle ) you will only get 6-8 Watts of heat per cell, which IMHO is too little to raise from subfreezing temps.

Its just so much simpler to hook up regular AC based heater with a thermostat.

The question remains, however, if the pack is fully charged at normal temp, but then you freeze it by sitting outside while you are at the office, how much energy is lost for your trip back home? This is key factor in deciding whether you need a DC heater to keep the pack warm using its own power, rather than just AC heater during charging.

Any takes on this?


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## JRP3 (Mar 7, 2008)

Where would the energy have gone? I can see how the cold would slow the charge acceptance but once it's in there and then cooled the charge should still be there. The discharge rate might be reduced so C rates might be less but I'd think the overall capacity of the cell would be about the same.


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## CroDriver (Jan 8, 2009)

JRP3 said:


> Where would the energy have gone? I can see how the cold would slow the charge acceptance but once it's in there and then cooled the charge should still be there. The discharge rate might be reduced so C rates might be less but I'd think the overall capacity of the cell would be about the same.


Take a look at the graph on the bottom

http://www.thunder-sky.com/pdf/200964145219.pdf


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## JRP3 (Mar 7, 2008)

Even down to -25C there isn't much loss of capacity, less than 10% of nominal. We're talking less than 10 miles on a 100 mile pack. Unless you are taking your pack to the max it shouldn't even be an issue.


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## Coulomb (Apr 22, 2009)

JRP3 said:


> Where would the energy have gone?


A good question. Note (from the graph linked above) how at lower temperatures, the voltage of the cell is lower, so even during the time when the voltage is above the knee, the same current produces less power. A separate effect seems to make the knee come earlier.

My guess is that it takes some thermal energy to "make the voltage appear", so with less heat in there, that chemical process is slower, and you get less energy out as electricity. So really where the energy went is "to the colder environment". Some of the energy is effectively stored in thermal form, and by allowing the cell to get cold, you lose some of the thermal component to the environment. By insulating the cell (thermally), you prevent leakage (in the form of heat) of the stored energy. Or perhaps it's more correct to say you lose some of the "catalyst" that you need for the stored energy to be recoverable as electricity.

Conversely, at higher temperatures, all chemical reactions happen faster. That seems to contribute to lower internal resistance, but unfortunately also to quicker degradation of the cell.

Edit: Now -> Note from linked graph

Does anyone actually know if that's close?


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## tomofreno (Mar 3, 2009)

> My guess is that it takes some thermal energy to "make the voltage appear", so with less heat in there, that chemical process is slower


During charging lithium ions enter the graphite lattice. They are bit too large to fit without introducing strain, so I would guess (and that is all it is) that when you cool the cell, thermal lattice vibrations decrease, making it more difficult for the interstitial lithium ions to get out during discharge. More work must be done against the lattice to move the lithium ions out, so a larger internal voltage drop and greater electric field is required. This would likely show up externally as a greater internal resistance in cold cells. To take it to the extreme, if the temperature was low enough so that the lattice atoms were "frozen" in place, no vibrations at all, the lithium ions could not be pulled out by the field unless lattice bonds were broken, requiring much higher energy. I think it is likely for the same reason that charging becomes more difficult at lower temperatures. More work and higher field is required to get the lithium into the lattice.

Tom


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## tomofreno (Mar 3, 2009)

> Tom, you could rig a heating element to the charging circuit, so the pack is kept warm during charge from the mains line, this way you don't need to waste pack energy keeping itself warm.


Thanks Dimitri, that is what I have planned. I have insulated the boxes somewhat with 1/2" polyurethane insulation, and plan to place several 6.5" x 8" 35W Farnam heaters on top the bottom insulation, sheet metal over these heaters for mechanical support of the cells as well as temperature distribution, and the cells on the sheet metal. I thought maybe over time, with road bumps and without the sheet metal, the ribbed bottom of the cells might cause cracks to form in the thin film heater elements due to flexing of the heaters. I plan to plug the heater controller to a 120VAC wall outlet and start charging when cell temperature reaches 50 F or so. It will be manual charger start and manual temperature read at first, but I think I should be able to automate it later (I mainly need to get everything installed and the car running first). The daytime temperatures here in winter are typically above freezing, so I think the car will heat up during the day and cell temperature will remain fairly high even if parked outside with no heating. My concern is that the cells will get too hot during summer, but it sounds like that may not be an issue. I also am hooking up a 150 cfm bilge blower to blow through the boxes and out the 2" pvc the wires are run in to the front of the car. I will just leave the lid off the box that is under the hood in summer. Of course I may have to modify all this to cool more in summer or heat more in winter, but I'll see how this works first, monitoring cell and ambient temperatures. I'll likely have to do some additional work to balance wintertime temperature of the boxes inside the car with the box under the hood also.

Tom W.


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## JRP3 (Mar 7, 2008)

tomofreno said:


> More work must be done against the lattice to move the lithium ions out, so a larger internal voltage drop and greater electric field is required. This would likely show up externally as a greater internal resistance in cold cells.


Which sounds as if this action should start to heat the cells up as you use them, thereby lessening the need for external heating.


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## Coulomb (Apr 22, 2009)

tomofreno said:


> ... More work must be done against the lattice to move the lithium ions out, so a larger internal voltage drop and greater electric field is required. This would likely show up externally as a greater internal resistance in cold cells.


Ah, that makes more sense. It didn't dawn on me that the linked graph was just showing higher internal resistance at cold temperatures; at 0.5C you don't lose nearly as much voltage as with 5C.

So here's my revised theory as to "where does the energy go". It's still there, just that as Tom points out there is a mechanism that causes higher internal resistance at cold temperatures. So you _waste _more energy getting it out when cold.

So as JRP3 says, as you use the cells they will warm up, allowing you to get more of the stored energy.

If this is right, and you lose say 10% capacity at 0°C, then if you discharged half the time at 0°C and half the time at room temperature, you'd only lose half (5%) the capacity.

Better yet, if you charge the pack at room temperature, and it freezes a few nights before you use it, but use it at room temperature, you should get the same capacity as if it stayed at room temperature the same number of nights.

In other words, the cold doesn't take the capacity away, only the _ability to access that capacity_. Does this seem to agree with others' experiences?

If true, this would also mean that charging at cold temperatures is OK for capacity, just a little wasteful (the higher internal resistance will cause the charger to draw power for a little longer). Note that there is a separate issue about charging below freezing. Google for a certain electric car with a LiFePO4 pack that burned to the ground. It seems that charging at below freezing may have caused that fire. So as long as all the cells' internals are above freezing, charging at low temperatures should (eventually) get the pack to the same SOC as at room or higher temperatures.


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## JRP3 (Mar 7, 2008)

The car that burned may have done so because of a balancer failure, which may or may not have been related to the cold.


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## RE Farmer (Aug 8, 2009)

So as JRP3 says, as you use the cells they will warm up, allowing you to get more of the stored energy.

If this is right, and you lose say 10% capacity at 0°C, then if you discharged half the time at 0°C and half the time at room temperature, you'd only lose half (5%) the capacity.

Better yet, if you charge the pack at room temperature, and it freezes a few nights before you use it, but use it at room temperature, you should get the same capacity as if it stayed at room temperature the same number of nights.

In other words, the cold doesn't take the capacity away, only the _ability to access that capacity_. Does this seem to agree with others' experiences?
[/QUOTE]

It's definitely true that discharging cold batteries heats them up and restores the warm state power. I used to fly turboprops that the batteries in cold temps would not drive the starter fast enough to start the engine. But, if one aborted the first start and waited a few miniutes for the batt temps to stabilize, they would be warm enough for a quicker and successful second start.


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## CroDriver (Jan 8, 2009)

Off topic question: The manual says that the cells come half loaded but all my cells are 2,6-2,7V. Is that OK?


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## EVComponents (Apr 20, 2009)

CroDriver said:


> Off topic question: The manual says that the cells come half loaded but all my cells are 2,6-2,7V. Is that OK?


You havn't tried to charge them up yet? They have been in route for a long time. They might self discharge some during that time.


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## CroDriver (Jan 8, 2009)

EVComponents said:


> You havn't tried to charge them up yet? They have been in route for a long time. They might self discharge some during that time.


I would love to charge them but I'm still waiting for my stuff! My charger should be in your warehouse...


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## Coulomb (Apr 22, 2009)

CroDriver said:


> Off topic question: The manual says that the cells come half loaded but all my cells are 2,6-2,7V. Is that OK?


Um, 2.6 to 2.7 VPC does sound rather low. Not dangerously low, but close to it. Usually lithium cells come from the factory at about 3.3 VPC. Are you sure of your meter?

Edit: maybe yours were chosen by EV Components for testing, and the the last test was a discharge? If that's the case (I have no way of knowing), it would have been nice to leave them at 40-50% SOC for transport, especially to a customer that may not be ready for charging immediately.


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## CroDriver (Jan 8, 2009)

Coulomb said:


> Edit: maybe yours were chosen by EV Components for testing, and the the last test was a discharge? If that's the case (I have no way of knowing), it would have been nice to leave them at 40-50% SOC for transport, especially to a customer that may not be ready for charging immediately.


Nop. Mine came direct from China since I'm located in Croatia.


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## Coulomb (Apr 22, 2009)

CroDriver said:


> Nope. Mine came direct from China since I'm located in Croatia.


Ah, of course. Well, ours did too (shipped direct to Australia) and all the cells we've checked had very close to 3.30 V.

I just checked a dozen more that haven't been charged or discharged: all read 3.29 V on my 3.5 digit digital multimeter. I believe mine were from the same batch as yours. These are all Sky Energy (blue) cells.


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## JRP3 (Mar 7, 2008)

I think Cro has the yellow TS cells. All my blue SE cells were above 3.2 volts and the data sheet that came with them showed the voltage around 3.27 when shipped.


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## 86Honda (Apr 15, 2009)

My yellow TS cells all showed 3.2 V when they arrived.


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## CroDriver (Jan 8, 2009)

I just measured with another multimeter. All cells are 3,29V. I apologize for my mistake, the battery on the other multimeter is low.



JRP3 said:


> I think Cro has the yellow TS cells. All my blue SE cells were above 3.2 volts and the data sheet that came with them showed the voltage around 3.27 when shipped.


Yes, I have 111 yellow TS 100Ah cells.


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## EVComponents (Apr 20, 2009)

CroDriver said:


> I just measured with another multimeter. All cells are 3,29V. I apologize for my mistake, the battery on the other multimeter is low.


That is a relief. Thanks for the update. I was starting to think we had a major issue here. My tech told me we have a ton (several tons) of batteries that are all 3.2V and have been for weeks right out of the box. Nothing done to them but quick volt testing.

2.6V would have been really unusual.


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