Originally Posted by
MrCjolsen
Today, it was right around 32 degrees, and I saw no decrease in run time. One morning it was colder, and the light cut out rather early, but that could have been due to some sketchy batteries in my collection.
32 degrees isn't really cold enough to make much difference. In my experience, down below 10 degrees F is where the dropoff really starts.
Here's a chart I found online that indicates that at -20C (the temp I was riding at the other day) you get about 20% of the normal capacity (80% loss). At 0C (your temp) you're over 80% capacity (20% loss).
http://dpfwiw.com/images/nimh_temp-capacity.gif
20% sounds about right - people say somewhat under 2 hours is normal with that light, perhaps 100 to 120 minutes. I got 20 minutes. The batteries were fresh so with a few charge cycles I could probably have improved it, but even if it added 50%, 30 minutes isn't good enough.
At the same -20C, LiIon performance drops to about 75% of room temperature performance.