Are lithium batteries worth the cost?
I can carry two group 29s in my AF1150. Are they worth it?
Forum Discussion
otrfun wrote:
My concern with LifePo4's would not be so much reduced discharge current capacity at lower temps, but the chance of permanently damaging the cells with *excessive* charge (and discharge) current at or below a given temp. I've always heard you should dramatically reduce charge current (or not even charge at all) below 0c (32f) with LifePo4 cells. I've heard -18c (0f) is a very similar type of cut-off for discharge current.
Did a cursory look for a graph that shows the maximum charge (and discharge) current and temperature relationship for LifePo4, but couldn't find one. Have you seen one?
As with most things, low temperature charging of LiFePO4 batteries is not black and white, it is shades of grey. Yes in general you need to be careful when charging much below -5C, and you should limit the current at these low temperatures (0.1C or so). Charging at higher current at low temperatures will decrease the battery life (but so will taking it below 50% SOC), but unless you go to the extreme it is not like it will be destroyed in the one cycle. This is not exactly what you are looking for, but it gives you an idea that even under 1C cycling, the increased aging at -5C is only very slight:
The whole paper is here: Journal of thermal analysis and calorimetry
As for discharging, besides decreased capacity at low temperature I am not aware of any cycle life issues discharging at low temps. If you can read the paper above, storage at low temperature (-20C) is actually beneficial to battery lifetime.
