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Thread: Bit of clarification on 18650 longevity

  1. #1

    Default Bit of clarification on 18650 longevity

    Hey all, was looking over some older threads and check out some of that battery university, was hoping for a bit more simple clarification. I was going to buy a couple more 18650 for backup, have mostly the Keeppower 3400 protected from illumn, was going to get a few of the Keeppower 3500s now. Just started looking around the forums, it was late, and I'm not sure if i read or interpreted some stuff correctly lol. I thought i saw a post that the panasonics werent that good for single cell flashlights? So i was hoping to debunk this mystery. And secondly, I thought i saw a post about 18650 lasting about 2-3 years, of course that battery university has alot of info and if this then that. I keep my batteries charged, in case of emergency, and i dont use my lights very often. id say once or twice a year ill take them all out of the lights and recharge them. It seems that this likely reduces their lifespan, but what I have these for is the emergency situation, and I am ok with having to replace them for wearing out from storing at higher voltages. What Im hoping for, here, is maybe some more clarification on if i should replace them every 3 years or so given my specific situation. My ac is on 77 most of the time so id guess these batteries are considered stored at this temperature, in my flashlights, in a bag next to the bed. The backups I will be getting will be stored in the same place, but in cases holding their charge and again, charged up once or twice a year. Any tips or input that might help here?

    So I guess in summary:

    1. have keeppower 3400, should i get more of the same or get keeppower 3500
    2. are these ok for single cell lights, is this even a thing?
    3. my batteries are stored at full charge and then topped off once or twice a year, barely used, some are kept in lights some in plastic cases - how often should i replace these?

    Hopefully this is specific enough that i wont get the if this then that lol, thanks for any responses.

  2. #2
    Join Date
    Jun 2014

    Default Re: Bit of clarification on 18650 longevity

    Without much use, they should last several years. I have 10+ year old laptop 18650's that still work fine.

    However, if you charged your cells to about 4.1v, rather than 4.2v, they will last much longer. It will give you about 90% charge level, and the batteries will perform for years longer. It's up to you to decide if losing that 10% charge is worth it.

    IMO, I'd probably replace every 3-5 years if you fully charge the cells. I'd raise that to 5-10 years if you charge to 90%. But in both cases, the cells will probably have lost about 20% of their capacity by the end of that time.

  3. #3

    Default Re: Bit of clarification on 18650 longevity

    Ok thats good news. I use a nitecore d4. I use it probably every other day for my eneloop aa and aaa for all the kids electronics, wouldnt be hard to just pop them out at 4.1, thx for that info.

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