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Thread: Best battery chemistry for infrequently used flashlight

  1. #1
    Join Date
    Mar 2018

    Default Best battery chemistry for infrequently used flashlight

    I'm new to the forum and have read much over the past weeks. My challenge is better understanding which battery chemistry may be best suited for an infrequently used flashlight; however, the light must work reliably every time I need it with no action on my part other than to turn it on. I've read Lion batteries tend not to do well if fully charged and allowed to sit unused for prolonged periods. NiMH batteries might need to be charged (topped off?) right before use; is this true for Low Self Discharge NiMH as well? I don't want to risk leakage from alkaline batteries. How do primary Lithium batteries handle a full charge for 6-12 months of no use? Better than LSD NiMH? Although not as environmentally responsible, infrequent use appears to favor primary batteries over the investment needed for rechargeable batteries and its very delayed break-even point, in my case. Other considerations? Thanks very much.

  2. #2
    archimedes's Avatar
    Join Date
    Mar 2011
    CONUS, top left

    Default Re: Best battery chemistry for infrequently used flashlight

    Hello and welcome to CPF

    Your post above has been approved, but the thread was moved to the Batteries subforum

    And, yes, you are describing a typical situation for which lithium primary is optimized.
    ... is the archimedes peak

  3. #3
    Join Date
    Sep 2007

    Default Re: Best battery chemistry for infrequently used flashlight

    Yes, if the capacity is suitable, a Primary Lithium battery has a very long shelf life, be sure to put them in a light with no parasitic drain (no electronic switches or status lights).

    A rechargeable Li-Ion battery actually has pretty good shelf life also, and leaving them charged to some level may not be that significant and issue in your situation, and quality NiMH LSD cells have low drain.

    To narrow it down; Just how infrequent is "infrequent"? When you do use it, for how long do you expect to use it for?

  4. #4
    *Flashaholic* StarHalo's Avatar
    Join Date
    Dec 2007
    California Republic

    Default Re: Best battery chemistry for infrequently used flashlight

    Primary lithium batteries can comfortably rest for roughly a decade of non-use with temperatures varying from -40 to 140 degrees F, they'll shrug off a few months in a drawer. If we're only talking ~ a year of storage, any of the battery types mentioned will work without issue.

  5. #5

    Default Re: Best battery chemistry for infrequently used flashlight

    You've gotten good advice about primary lithium, li-ion, and low self discharge (LSD) NiMH cells. Under no circumstances use alkaline or "heavy duty" cells unless you want to find a solid glob of corroded junk in your flashlight some day. On the flashlights I use only very occasionally, I unscrew the end cap until the light won't turn on, to guarantee that there's no parasitic drain. If anyone else might need to use the light, I tape a note to it warning that the cap must be screwed down before use. Usually lights having a switch that has a solid click actually disconnect the power so unscrewing the cap isn't necessary, but it's good to be on the safe side if you're not able to verify it.


  6. #6

    Default Re: Best battery chemistry for infrequently used flashlight

    AA or AAA with Energizer Lithium Ultra batteries installed... lockout/ slightly unscrew battery tube/ tail cap if there's any question of there being any parasitic drain from electronic switches/ micro controller in the light.
    Then you should have a light on hand with a reliable 20 year or so battery installed and ready to go, just tighten the threads and turn it on.
    The brighter the light, the darker the shadow.

  7. #7
    Flashaholic* ronniepudding's Avatar
    Join Date
    Sep 2013
    NY Capital District

    Default Best battery chemistry for infrequently used flashlight

    I try to use rechargeable cells wherever practical, so all the lights around the house use Eneloop/NiMH fuel, or 16340 Lithium Ion depending on form factor. For the most part, these house lights are used frequently for short duration, and sheer redundancy means that no single light is critical. Some of these house lights - the ones located in out of the way places like the basement or garage - may sit for more than a year without use or recharging, and I think LSD NiMH does fine for that use case.

    For lights kept in the cars, I use Energizer L91/92 and CR123A primary cells. 10-year shelf life and performance in temperature extremes makes those chemistries a logical choice ... use is infrequent, but reliability is critical.

    I also keep a small stash of Energizer L91/92 and CR123A primary cells in the house for emergencies such as power outages, etc. However, thatís more of a flashaholic/geek thing than a practical concern... only in an extreme disaster situation could I burn through all the rechargeable cells in the house before having the option to recharge.
    Last edited by ronniepudding; Today at 07:50 AM.

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