Originally Posted by Spld cyclist

With my lithium ion lights, I've seen about a 15 - 20% reduction in runtime between summertime temperatures and below freezing temperatures. These are on-bike times. I haven't really tried running lights just in a room to see how long they will run under that condition. What the OP is describing is a > 63% drop in runtime, which is really surprising to me. I looked at the product page the OP linked, and it indicates "Runtimes of the two PID controlled levels (1100Lm and 670Lm) vary greatly with ambient temperature and air circulation." That seems to indicate that the air circulation factor is what is really at work here.