Tesla isn’t for everyone, and it will never be…
Getting back to the bicycle lights and performance of batteries in cold winters. All chemical reactions are effected by temperature, batteries are no exception. Of course, depending on the chemistry of specific battery, it may be effected by temperature more or less.
My usual solution to keep Li battery performing well at fairly low temperature while bicycling is to slip the battery inside my jacket pocket and connect it to the light using a minimum of 20G wire. Body heat keeps the battery warm enough to have it last close to normal times. During really cold weather with snow on ground, my commuting time does increase significantly- some times up to 1 hr on bad days but never an issue with batteries (a 4 battery pack, connected 2px2s).