On Sunday, March 18, 2018 at 1:23:04 PM UTC-4, Dan Daly wrote:

The capacity graphs for 25, 0, -20, -40 C ( https://starkpower.com/product/12-volt-9ah-battery ) tab at the bottom shows they're good batteries down to 0 C, but perhaps a poor choice for the real cold.

They don't specify the discharge rate, and it's probably much higher than typical glider use. I've taken LFP batteries to 31,000', they worked fine.

Evan Ludeman / T8