Did you try issuing chargeback?

But I believe you shouldn’t charge batteries in very cold conditions (below -10C?)

Yeah, that’s much closer to the equator than I am. While this would work for me in the summer it may not in the winter - when temperatures drop well below 0 degrees Celsius (making charging less effective) , and the sun does not shine for that long (shortening the charging time significantly).

Will that be enough during winter?