How low do you go? When do you swap and charge your cells?

Most cells minimum recommended voltage is 2.5-2.8V it seems. So, how low do you guys discharge your lithium ion cells before you stop using and charge them? I notice that some new lights can hold turbo without any indication of decline until cells are 3.0-3.25V right after use but, is that too low for a modern high discharge IMR or NCR 18350 or 18650 for instance? Will you still get good life and hundreds of cycles at a respectable capacity discharging that low? Thanks.

I generally try to not go below 3.2v but I did let one slide recently to 2.85v and it charged up just fine.

I recently had a 14500 drop down to 2v due to parasitic drain before I caught it. I posted a thread about what to do here. One comment was that even if the cell recharges and appears to be fine, there is a possibility that spikes have been formed in the electrolyte, which could pierce the dividing membrane and create an internal short, with the usual dire results. I admit I have continued to use the cell, but I put it into a light it wouldn't bother me to lose, and am aware of the increased possibility of danger when I use it.

3.6v

mainly because I don't want to end up with a discharged torch in some place. Never drop them below 3.6

On my bigger lights like the K60 and K70, I never drop below 3.6v.

Whereas the HL55 headlamps get taken to 3.2V.

When my X7 will no longer stay in ludicrous mode.

I try to recharge them around 3.7 to 3.8 v unless emergency situations occur(volunteer firefighter).

I go down to 3.33V. Easy to remember.

I am already worried when they reach 3.8v. Lol...

Newlumen said:

I am already worried when they reach 3.8v. Lol...

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Remember, a cells capacity is based on draining to its minimum voltage(usually 2.5-2.8V). Most chargers capacity tests drain to at least 3.1V if not 2.8V. The cell is still 50%+ full at 3.8V. You can definitely go lower then that.

What do you think HKJ? What is a good minimum resting voltage to strike a good balance of capacity and cycle life?

Unless I've only used a light for a few minutes, I always fully charge my li-ion cells after use. It may shorten the lifespan to a few years, but a full battery is a lot more useful than a not full battery when you need it (e.g. an unexpected blackout). Anyway, I'm sure by the time my newer li-ions need replacing in a few years time, there will be even better cells available (such as the long rumoured 4000mAh Panasonic 18650).