Quote:
Originally Posted by CroDriver
They are available.
I already tested them.
They have 12,65 Ah capacity.
The temperature raised from 16 C to 56 C at 10 C discharge current (120A).
I measured a maximum 690 A (57C) but that damaged the cells permanent. 15-20C is safe
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Based on the limited information that I've come across regarding safe temperatures with LiFePO4 cells, 15-20C might be safe but if 10C is pulling 56c temperatures, that is pretty close to the limits and would be as far as I'd like to take them. The FMA document estimates that A123 cells lose cycle life dramatically after passing 140f(60c) temperatures, I'd say that this makes sense as Thunder Sky and other prismatic manufacturers seem to put 55c as their top specified temperature.
I'm sure they are great with 20C or possibly even beyond as a short term pulse discharge but if they are getting beyond 60 Celsius on a regular basis, I'm curious as to how long they would last. I'm not sure what use, other than in the RC community that anyone would have for anything more than 20C continuous, especially considering 20C is a 3 minute discharge.
I see situations like replacing NiMh cells from a hybrid pack where they pull about 100 amps(15C) from 6.5Ah packs where a high draw capability would be useful. In fact LiFePO4 is already used like this now, but those who are replacing their hybrid packs with higher capacity ones like the idea of using cylindrical, especially the 38mm diameter size since it is only slightly larger than the D NiMH cells used in Honda hybrids and minimal modification is needed to the physical case to slide them into position so the pack is neat and looks just like the stock system but with more capacity and it leaves the ability to utilize the systems built in cooling and heating from the HVAC system if its needed under high loads or cold outside and needs to warm up a little.
CroDriver, did you catch the voltage that they maintain with 120 amps draw with these cells? And at what SOC roughly did you measure it at(if you did measure)? Thanks
I was thinking of going with the 40120 cells and skipping the OEM case to get 16Ah but knowing what 10C provides with voltage sag on these 12Ah cells will give me a ballpark idea if the 16Ah cells might be able to do it. ...otherwise it would probably be 38120P 8Ah cells but I'd have to have samples to test of those to see if they could handle it before I buy the 52 cells(plus a few spares) that I would need.
Re: headway 38140S(3.2V12Ah) lifepo4 cell available now
Re: headway 38140S(3.2V12Ah) lifepo4 cell available now
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