Originally Posted by
Tourist in MSN
.....
I called Peter White a few years back and asked if there was a problem using my B&M Luxos U (now discontinued) headlamp in sub freezing temperatures. If you are not aware, that dyno powered headlight has a pair of built in Li Ion batteries. He said he had never heard that about Li Ion batteries and sub freezing temperatures, so he suggested I would have no problem. But I chose to unplug my dynohub whenever I rode that bike in subfreezing temperatures anyway.
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)