Originally Posted by steelbikeguy

The battery manufacturers are pretty clear and consistent about how they want their lithium-ion batteries treated, and they publish their recommendations on their web sites. This is what Panasonic said when I last checked:




For this discussion, the key points are that you shouldn't charge them below 10 degrees C, and shouldn't discharge them below -10C.
-10C is 14 degrees F, which is as cold as most(?) cyclists will ride, so it's probably not a big impediment.

For things like standlights, which will be getting charged when the bike is ridden in the cold, it's probably best to use a super capacitor instead of a lithium-ion battery. Interestingly, NiCad batteries are much more tolerant of charging in very cold temperatures, which is what I use in my home-built dynamo lights. Nicads are pretty nearly impossible to buy now, so I expect to switch to supercaps for any future work.

Steve in Peoria (where is it is currently below 0F)