Battery for my Gemini light. It's been good for a couple seasons, maybe three. I usually do rides of 1 to 2 hours never and issue. Usually run the brightness at all levels all ride. One ride last week using more high than I usually do it drops to low at about an hour. last night I'm riding Seymour and the light is off all the way up Old Buck. On sporadically up Baden Powell to Severed where It's on high most of the way. Halfway down Asian Adonis poof, low again. Maybe 15 minutes use. I know Li ion cells have consistent performance until they die quickly but I did not think that they would die this fast. Only recently though I have put the battery in my pack as opposed to a rear pocket where the battery is warmer.
Is 8 or 9 C cold enough to make a battery like run this badly? I wouldn't have thought so because the Niterider on the bar has worked well although it's battery is starting to drop off too. Ordered a new Gemini battery anyway. Might take a while to show up though.
My gemini light has a feature that makes it switch to low when it overheats. I guess it's a useful feature but it sure is inconvenient when actually riding. I usually experience this early and late in the night riding season when it's not freezing cold