Re: Worth going to P60 with 18650?
Lithiums are great. Lots of capacity - they hold their charge very, VERY well and have a good discharge curve. Going up to the next battery size will also open a plethora of light options you just don't have right now. What's the brightest light you can get on AA's, the Fenix L series? Bust through the 180 lumen ceiling!
(I could be way off, there might be more options than I'm aware of . . I'm still new here!) Of course a home-made, large light (like an ROP or a Mag85) can use multiple AA's and I'm not referring to those.
The chargers aren't that expensive . . . AW sells a decent one for under 20 bucks, I believe.
But li-ons are not perfect either. They have a shelf life (using them or not) of 2 to 3 years which can be significantly shortened due to ANY misuse. They don't want to be overcharged, or drained too far. That's what the protection circuitry does . . . protect you from a nice little gooey flame - and that has happened. They don't like the cold. If you leave them in a car in the winter, a fully charged battery will act like a 1/2 charged battery or less.
Here is the latest thing that is starting to bother me about them: You are supposed to store them at their nominal 3.7 volt state. That means they're nowhere near fully charged. The optimal use is to charge them then start using them right away. You shorten their life by leaving them fully charged, ESPECIALLY if you do that in an hot environment (like in your car in the summer). This bugs me because I was starting to set myself up where all of my lights would use 18650 cells. Well I talk about my lights far more than I use them. I like them standing by for months on end and I prefer to leave them fully charged! I like leaving them in my car, ready to go. But again, all of that just shortens their lifespan, it doesn't kill them immediately. The biggest thing is to not over charge them or drain them too far.
I hope I didn't scare you off. They're the next best thing to the CR123, which would be perfect if you could recharge it!! CR123's don't have any of the storage, hot or cold issues I described above.