One year in the glovebox for an 18650 li-on battery

Attention: This content is 3 years old. Please keep its age in mind while reading as its contents may now be outdated or inaccurate.

I’ve seen arguments online about whether keeping an 18650 battery in your car is a good idea or not. I always remind people giant banks of 18650’s power Tesla’s, laptops, and power tools, all of which see all kinds of use and abuse in all kinds of climates.  Still, I have seen people insist that the wide temperature ranges will somehow kill an 18650.  Well, a year ago I decided to toss one of my 18650 powered flashlights in my glovebox to see how it would fare. I used it on occasion over the last year and did not charge it at all. I pulled out my multimeter and checked it last night and would you look at that…

Sitting at 4.05 volts. Like I said, I have used this flashlight a handful of times, so this is basically still a full charge. A full charge would only be about 4.1 volts anyway, so the small drop is just from my use of it. Tested and verified, I have no qualms about leaving an 18650 powered light in my glovebox for years to come.