I bought it thinking it was usable went to charge it and was like fuuuuuuuuuu.@letschat7, that looks pretty nasty, but 20 years is a pretty long time. I think my oldest Li-ion cells are about 7 yrs old. I've only ever had one fail, and it just pretty much went dead all of a sudden. I think the protection circuit may have failed. There was no venting or event. When I tested it, nothing registered at all, so I got rid of it. I believe it was a Nitecore 18650. All of my Li-ion batteries are protected Fenix & Nitecore, and a few Acebeam & Imalents that came with the lights. Most of them have not really been charged very many times.
What exactly is the fear here leaving cells in lights in series specifically?
Is it worse to you than a single cell? Why?
As far as parasitic drain, why is it a worse issue in a multi cell light?
And on parasitic drain, if your light has an electronic switch, it has it. If it's a mechanical switch, it doesn't
Yes, I do, but most of them do get used a little here and there. It's just that I have a lot of lights, so I try to use most of them a little in order to keep cycling the batteries, but it takes quite a while before they actually "need" to be charged.Honestly, sitting around for 6 months to a year unused; grab your charger and top off those rechargeable cells before using the light.