Hi all, I need some education here. I just found out about 16650 lithium ion batteries and ordered a couple for my Surefire flashlights—love not having to use cr123s. I have a Nitecore D4 charger that I've been using with my nimh and other 18650 lithium ions and has worked great but it doesn't say it is ok for 16650 batteries on their website but other chargers on their website like the new i2 and i4 say they are good for them. It is the same voltage as 18650's right? Wouldn't it be ok for 16650s as well?
Here's the deal...unless you're buying no-name generic Chi-Com 16650s, the good ones that we have access to are made by Sanyo--UR16650 either v.1, or v.2.. The difference between the two is that v.1 is actually a 4.30v ~2100mAh cell and v.2 is a 4.35v 2500mAh cell.
Since a lot of these have protection circuits thrown in, they become a 17670 due to added width of the metal strip and length add by the PCB. 17=17mm W, 67=67mm L and 0= is a cylindrical cell.
Here's the second caveat: since there's a protection circuit added, one can't charge the cells up to either 4.30v, or 4.35v, since that's something a protection circuit does--it's a feature, so you won't be filling them up to their max capacity.
Another issue is finding a charger to charge 4.35v cells up to 4.35v and your NC D4 doesn't do that.
If you're running protected 16650s, then any capable li-ion charger will charge them up to 4.20v, but since SF lights are designed 'mostly' around 6.0v (2xCR123As), you might want as much voltage as you can get, unless you've replaced the P60 drop-in with some geared for 4.20v. So you would probably want the naked cells, something like a smaller Liitokala Lii 100s or 202 charger, which charges up almost anything we can throw at it.
Protected 16650s vs. naked 16650s?
4.20v, protection and slightly less capacity vs. 4.35v, naked/no protection circuit, ~2500mAh capacity?
You can get by without button tops because the P60 has a spring.
Just some things to consider.
ETA:
I have added a Redilast 4.20v P60 3 mode XM-L2 to my 6P and bought two of the Redilast 17670s that are v.1 Sanyos 4.30 ~2100mAh cells. I can only charge them up to 4.20v, due to the fact that they have PCB added.
Still, since I never use the light, they're fine.
Chris