# Thundersky 200Ah temp test



## dimitri (May 16, 2008)

Thanks a lot for the test. I am glad it confirms the data I got from Great White North  earlier, and confirms my calculations for LVC temp compensation. Awesome!!!


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## CroDriver (Jan 8, 2009)

I drove today a few miles. I have 50cm snow in front of my door and a -10 C temperature. The resting voltage of my TS LFP 100Ah cells was about 3,25V (charged for the first time a few days ago, drove about 10 miles since then at heavy loads). 

The voltage drops to 2,7V at 500 Amps.

I have no BMS or any other sophisticated monitoring method. I'm just using a standard multimeter connected to one cell for now


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## MN Driver (Sep 29, 2009)

Thanks for the test information. I still think it's best that these cells be kept appropriately warm based on the climate that someone lives in. I live in Minnesota and have directly experienced -30f/-34c temperatures, I plan to actively heat whatever cells I use before/while charging and I am planning out a prototype open-source 'heated jacket' design that might inspire ideas for pack heating for any chemistry using mostly stuff that can be found at any hardware store. My idea hopefully will create a feasible way to keep cells warm while being parked for about 10 hours with hopefully minimal drain on the pack, I'm thinking using a 150 watt heater in a creative way behind insulation (so <1.5kwh to keep a single pack box isolated from outdoor temps for 10 hours). I see people using rigid insulation which without a good air layer, doesn't help as much as it could. I'll create a seperate thread when my idea once I'm able to diagram it a bit. It might be an overkill solution but for temperature extremes in the north near Canada and in Canada, it might help against this sort of sag. I'd prefer to keep above 2.5 volts whenever I can and with a 550 amp controller that would pull nearly 3C, I'd imagine that I'd be dropping below that threshold with a freshly charged pack that got cold, I can't imagine the start of my commute which begins with a fairly nasty uphill acceleration on the highway to 55mph which requires a heavy bit of throttle in good conditions with a gas car. I'm thinking 50% SOC, -35c and the uphill on the highway as my worse condition, and AC setup that has regen and I'd prefer charging at above freezing, my conditions may be worse than others but I don't know how long any cells could handle the cold without heat or otherwise a well insulated box to keep them from dropping below a freezing temp after leaving the electrical outlet that may have heated them when back at home.



CroDriver said:


> I drove today a few miles. I have 50cm snow in front of my door and a -10 C temperature. The resting voltage of my TS LFP 100Ah cells was about 3,25V (charged for the first time a few days ago, drove about 10 miles since then at heavy loads).
> 
> The voltage drops to 2,7V at 500 Amps.
> 
> I have no BMS or any other sophisticated monitoring method. I'm just using a standard multimeter connected to one cell for now


This seems even better than the test above and Tesseract's test was promising but yours makes them look even better at 5C, no less!


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## gdirwin (Apr 7, 2009)

Tesseract - when did you buy your TS200AH cells?

Just curious if they were the "new" LiFeYPo4 cells (ie Yttrium) or older TS cells... The new cells claim operation at -45C, whereas before it was -25C...

Just trying to figure if Yttrium is all hype or if there is some advantage of the new TS cells in cold weather...


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## Tesseract (Sep 27, 2008)

gdirwin said:


> Tesseract - when did you buy your TS200AH cells?
> 
> Just curious if they were the "new" LiFeYPo4 cells (ie Yttrium) ...


The datasheet that came with them says they are LiFeYPO4. 

Sorry, but I'd have to go get some dry ice to be able to test any temperature colder than what a freezer can manage... I'm in Florida, after all


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## Tesseract (Sep 27, 2008)

MN Driver said:


> ... I live in Minnesota and have directly experienced -30f/-34c temperatures, I plan to actively heat whatever cells I use before/while charging...(so <1.5kwh to keep a single pack box isolated from outdoor temps for 10 hours).


This seems like a good idea to me, as just letting the cells drop to -30C is just plain brutal but to then pull high currents from them could very well be the proverbial straw that breaks the camel's back.

That said, since the internal resistance of the TS cell almost doubles when going from 21C down to -8C, it's reasonable to conclude that once you start pulling some serious currents from them they will heat up much more rapidly than the same cells at "room temperature".

What I'm saying here is to not overly complicate matters until you've determined you need to overcomplicate them 




MN Driver said:


> This seems even better than the test above and Tesseract's test was promising but yours makes them look even better at 5C, no less!


Yep... though if you want to drive for more than 10-15 minutes you need to keep those 5C moments to a minimum... 

And since internal resistance goes up quite a bit as temperature goes down, pulling 5C when the cells are cold could result in localized hot spots inside the cells, maybe even permanent damage. 

So, while it makes for nteresting data, I would say trying to pull 5C from your frozen LFP cells is just a bit on the risky side.


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## NYCElectric (Jul 14, 2010)

Tesseract said:


> The datasheet that came with them says they are LiFeYPO4.
> 
> Sorry, but I'd have to go get some dry ice to be able to test any temperature colder than what a freezer can manage... I'm in Florida, after all


I know the point was to stress them and test the claim, but if you're in a hot (ugh and muggy!!) climate like Florida, why do you want to verify that super cold temp if you won't be running into it?

Thanks!

-NYCE


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## Tesseract (Sep 27, 2008)

NYCElectric said:


> I know the point was to stress them and test the claim, but if you're in a hot (ugh and muggy!!) climate like Florida, why do you want to verify that super cold temp if you won't be running into it?


Well, we actually *did* get some pretty f'in cold temps this last winter. 10 nights straight below freezing and the days weren't much warmer.

But this was more in the interest of science and for our conversion shop partner, Rebirth Auto, because they were converting several cars that were going to the Netherlands.


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