What's better for the health of a cell?

Say you've a few flashlights that get occasional use whether in an EDC rotation or around the house. Maybe use it 5 minutes one day and 10 minutes two days later. Is it better for the cell to let it drain some before charging, say to 3.7-3.9V, than to constantly top off from 4.1V? Is this even more true for a light that gets very occasional use?

I've been EDCing my SC62w the past couple weeks with varying use each day. I measured the voltage yesterday and it was about 3.75V, probably time for a recharge though I've been aware the battery checker has gotten down to 3 flashes (<3.95V in my light) the past few days. I keep a TN12 in my bag as a backup, and it gets rare use these days. It's been used sparingly in the last few weeks and it measures 4.08V. So is it worth it to keep it topped off or to run it down to 3.8-3.9V or so before charging even though it may take 2 or 3 months to be used enough to get to that voltage?

So what's better for the health of the cell? Do you constantly top off or let them drain a little bit?

cells are cheap. life's too short to constantly babysit them

but to answer your question, keeping them cool and as close as possible to the storage voltage, around 3.7 to 3.8v should make them last longer. but of course you'd be sacrificing a lot of reserve capacity which may become useful in an emergency

Certainly you will come to a happy medium with your illumination. If it was me, I would take the TN12 batteries off the charger after it reaches over 4 volts or more, not going all the way to 4.2V. So that if the resting voltage of that battery is 4.1V (about). Then I would not recharge it until it gets in the 3.8V range UNLESS you know you will be using it in a sustained manner in the near future (or an electricity impacting storm is coming your way) which then I would go up to fully charged.

For your excellent EDC, the ZebraLight SC62w, I would charge the battery the same as your TN12 (not quite fully charged), and keep your spare battery the same way, unless a 'storm' approaches. If you let the cells go to fully charged, use them some, until their resting voltage is at the level you are comfortable with.

How much longer will your batteries maintain their usefulness with this regimen, compared to just 'filling them up' and letting them sit until they reach 3.7-3.8V? Probably not a whole lot more, if you don't let your batteries cook in a hot car or severely discharge them. The extremes are what lessens their potential. Having said this; For a number of years, I fully charged two pairs of Ultrafire batteries (for a 2 cell torch) charging them when they started to not be able to go on high-mode in the flashlight, and they were fine. Since I joined candlepowerforums, they have been retired. They no longer reach 4.2V resting, and get considerably warm during the charging process, due to the internal resistance.

Do what fits your nature, not worrying about what our fastidious CPF members like to do.

Like someone said above, cells are cheap. Probably just over thinking it, but was curious for curiosity sake.

On my EDC lights that don't use primary cells, the batteries get charged every two weeks.

My throwers, get charged monthly even though the lights are locked out. Most having more than 4 cells require two or more chargers, so I just grab a light and replace with a freshly charged set and cycle the batteries into the routine.

Having extra cells is the key though. At least one set of extras is required for cycling purposes.

Yeah for my SC52w I have two 14500s I cycle every time I charge. I could always swap out the battery in my TN12 with my SC62w to give it a workout every now and then.

uofaengr said:

Yeah for my SC52w I have two 14500s I cycle every time I charge. I could always swap out the battery in my TN12 with my SC62w to give it a workout every now and then.

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That's a good idea.

Overclocker said:

cells are cheap. life's too short to constantly babysit them

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This is the thinking I adopted after worrying about cells for a fair amount of time. Charge up to about 4.17v (that's what my charger seems to do anyway) and forget it. After you get so many lights, you either have to take up a new hobby of babysitting batteries, or just use and enjoy them!

markr6 said:

This is the thinking I adopted after worrying about cells for a fair amount of time. Charge up to about 4.17v (that's what my charger seems to do anyway) and forget it. After you get so many lights, you either have to take up a new hobby of babysitting batteries, or just use and enjoy them!

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+1

The charger and occasional MM do the work for me, i just enjoy using the mah

I usually will wait until the charge gets under 40% before charging but if I am not going to have access to a charger for awhile I make sure to charge my phone before hand. Typically it gets charged every 3 days or so. It usually will get a daily charge so I'm not worried about being too much below 40%. Every once in a while though I'll try to drain as much as I can get out of it. I tried doing the 40-80% routine but then the battery would die on me too often. Since I have been topping off the charge the battery has been much better.

It's funny how I, and probably some others, treat phone batteries differently than flashlight batteries. We are either running our phones all the way dead or are constantly topping them off.

But the philosophy I've kind of taken now on my flashlight batteries is that if they're for a light I consider a "burner" like any of my custom or modded lights or my new BLF A6, even if I moderately use it that day and it's only between 4.0-4.1V, I will charge it up that night. Never know how much I'll need it the next day and I'm not bashful to use turbo modes.

I personally don't care about my phone. My phone is for my use when I need it, just like my lights.

Frequently I turn the phone off unless I'm using the internet for a quick lookup. I can do without the phone.

My lights need to operate when needed and forever how long they are required.