When do you charge your 16340?

I have the Fenix E15 that I use a 16340 battery. I'm curious as to when users of 3.7V batteries decide to charge them. I checked the voltage, and it measures 3.36. Since it's a dual power use light, I still have 4 modes, but it will no longer output 450 lumens. I can tell a difference in each mode, so I'm assuming turbo is now 270 lumens if I was using a cr123. This really doesn't bother me with less output on turbo. I guess my question is what do you do? Do you keep using it as is until maybe one or two modes work? Or, would you replace/charge the battery to have the highest output? Is there any harm to topping these batteries off, or fully depleting them from use? I'm using Fenix batteries.

charge mine when the light wont do turbo anymore or immediately drops from turbo or better yet when the light only comes on for a few seconds then shuts off. Im using Keeppower 700mah 16340's

I charge mine as soon it drops down from Turbo. I should add, or 3.6-3.7V whatever comes first as that is storage voltage and I have more then one cell to rotate through.

I recharge any 16340, 18650. or 26650 when voltage drops to 3.6 volts. I always carry spare batteries.

It seems so far, that most will recharge when turbo is no longer an option.

dbld49 said:

It seems so far, that most will recharge when turbo is no longer an option.

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That would be a very good start to when it is time to charge a battery. With time and experience you might have better ways to know when to recharge, but you will never have the full potential of a rechargeable lithium ion battery when you go lower than 3.5 volts.

I think so you should use it from to time to prevent it from rust and damage.