I have used LiFePO4 batteries, only in discharge mode, by down to -15 deg C (charging was done 'back to the warmth'), and they worked fine. But from what I read it looks like Li-* batteries do not like to be charged by minus temperatures.
I would like to use large LiFePO4 cells with a solar panel by negative temperatures (typically -15 deg C, may be down to -30 deg C). I will have quite low charging currents, max 1 to 1.5Amps for a 40Ah cell. Do you think it may be OK to charge at such low rates (this guy seems to say no: Solar powered single cell LiFePo4 charger circuit ; but here it sounds like very low charge may be ok http://batteryuniversity.com/learn/article/charging_at_high_and_low_temperatures)?
Has anybody more specific experience with this? Or has anybody knowledge of a place where I may get military / space grade cells that accept cold if usual LiFePO4 is a no go, or alternative battery chemistry solution? FYI, here are the cells I use as by now: