# Capacity vs discharge rate (temperature) of A123 pouches



## rwaudio (May 22, 2008)

While discharging at 2C (100% to 0% to measure capacity) the cell gets a tiny bit warm, I would say just above ambient, more like skin temperature. When discharging at 0.5C it doesn't get above ambient (21deg C).

I'm consistently measuring higher capacity at 2C than 0.5C, it's only 0.3Ah to 0.4Ah (18.04 vs 18.36Ah on the last cell for example) but it's interesting regardless. I only did 1 or 2 cells at 1C with this set up and it was lower than both 2C and 0.5C and was cold like the 0.5C

At what temperature are the cells most efficient? A123's have lower IR so it takes higher currents to warm them up. When I was testing headways it was easy to see the voltage climb back up after an initial drop during high current discharges because the cell heats up. The A123's don't do that, at least not at the discharge rates I can perform on the bench.

Does anyone out there have the capability to measure discharge capacity at the same time testing at different temperatures? IE a single cell charged and discharged at 10Deg C, 20 C, 30 C, 40 C. Maybe there is a sweet spot that it would be worthwhile trying to maintain in an A123 pack. Perhaps that's how A123 might actually get 20Ah's out of one of these things.


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## FWD (Feb 3, 2012)

http://www.diyelectriccar.com/forums/showthread.php?t=69550&highlight=A123

OK

i have 72 20ah of these A123 from china build in korea and made in usa

now i have 72 bleeding boards that are for thunderskys so they start bleeding at 3,68 volts and at 3,7 are bleeding around 200mA. 3,8 300 max

i charged a cell up with a bleeding board and it stayed at 3,69 volts with 100mA of charge 

after i did a higher current fast charge to 3,7 then stopt where it dropt below 3,69 and put it in 0,1a where it went up to 3,69 and stayed there

then i discharged 16ah over 16 hours with a 1 amps disharge current
the end voltage was 3,202
so there is a lot more in the cell?!

i am now discharging again from 3.202 to see when it hits 3,0 volts

i wonder if its a smart thing to do and charge to 3,69 instead of 3,65 volts?
would this shorten the life?

i use these bleeding boards to top balance the cells at 3,69 volts.


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## LithiumaniacsEVRacing (Oct 9, 2010)

Hello all,

I am looking for the specs on these A123 Amp20 Pouch cells (Factory Data), I have read they can produce 750 burst amps, but for how long? 3 seconds, 5 seconds? Does anyone have this data? And how low does the voltage drop at 750 amps?

Thank you!


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## rwaudio (May 22, 2008)

LithiumaniacsEVRacing said:


> Hello all,
> 
> I am looking for the specs on these A123 Amp20 Pouch cells (Factory Data), I have read they can produce 750 burst amps, but for how long? 3 seconds, 5 seconds? Does anyone have this data? And how low does the voltage drop at 750 amps?
> 
> Thank you!


Hi Ron,
I can't test at 750A I believe the highest tests I did were at 350-400A on a single cell.
If I recall the voltage stayed at or above 2.8v for the first 5-7 seconds, I don't think I did tests longer than that because the resistive load was burning my bench.

If the cells could actually put out 750A I would guess they would sag to around 2.5v

I believe Jack R tested to around 475A I don't recall his results though, it was a few episodes ago and unless I'm mistaken it was on a multi cell pack, so the results are at the mercy of his assembly method and technique.

I'm sure you got the 750A number from Mavizen, but as the one and only official distributor hopefully their specs are correct.


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## LithiumaniacsEVRacing (Oct 9, 2010)

Thank you for your info. I really need to know how long these cells can produce 750amps, I am sure Mavizen has the data, maybe I need to ask them. If anyone has the 750 amp data, please post it, thank you.

I have other projects in the works and need a higher density cell than our Haiyin Racing cells. The A123 pouch cells seem like a nice fit. Last I contacted Mavizen was many months ago, I think they quoted me $65.99 a cell. I need to get updated info to build this new pack. 



rwaudio said:


> Hi Ron,
> I can't test at 750A I believe the highest tests I did were at 350-400A on a single cell.
> If I recall the voltage stayed at or above 2.8v for the first 5-7 seconds, I don't think I did tests longer than that because the resistive load was burning my bench.
> 
> ...


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