Battery Longevity question for the bike light pros out there...- Mtbr.com
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  1. #1
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    Battery Longevity question for the bike light pros out there...

    Question...what is the longevity of a good quality (gemini, gloworm, lupine, etc.) battery. In other words, how many years of use will you get before they become unusable and does the number of charge cycles significantly affect their lifespan?

    And any recommendations for replacements.

    Thx!

  2. #2
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    It’s the number of [complete] recharges that effects their life span. Seems every battery is rated for up to 500 such cycles, be difficult to test that in real time! I still have cells about a decade and a half old that continue to perform quite well. The weak point in any system that employs external battery packs is the cables/connectors, which can fail at any point in their life.

    General consensus seems to be that the best 18650 batteries available right now are the Sanyo NCR18650GA 3500mAh 10A. But you shouldn’t have to worry about replacing any of the ones that come with the brands of bike lamps you mentioned for a long, long time.

  3. #3
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    Quote Originally Posted by rixsurfer View Post
    Question...what is the longevity of a good quality (gemini, gloworm, lupine, etc.) battery. In other words, how many years of use will you get before they become unusable and does the number of charge cycles significantly affect their lifespan?

    And any recommendations for replacements.

    Thx!
    A battery pack that is using the best brand name cells should last a good many years. All batteries lose capacity over time. How fast they age will depend on how often you use them, how deeply you discharge them when in use and what voltage you store them at when not being used.

    I have packs that I've owned for more than 5 years but I don't do a whole lot of night rides using them. When I do use them though I usually don't ride more than two hours so I doubt that I ever deeply discharge the cells.

    If you are a person who routinely rides night on a regular basis I would think it a good idea to do a run time test after the first two years and then do one every year after that. Once the battery pack appears to lose more than 25% of it's capacity ( or equivalent run time ) you might consider buying a newer battery pack but all this depends on whether or not you really need the extra 25% in order to finish your rides.

    Back in the day I did all my night rides using packs that had a capacity of between 4000 and 5200mAh. I used those packs for years and never ran out of juice while on a ride. All of my current packs now were over 6000mAh when new. I'm sure they have lost capacity over the years but for my two hours rides they should be good for a long time. Keep in mind that a lot depends on how you use your lights as to how it relates to run time. If you run your lights at maximum output most of the time ( and you have bright lights ) you will likely need new packs more often. When mtn biking I usually run my bar light around 500 lumen and my helmet lamp at about 600-800 lumen. I don't run the maximum outputs ( for me that's 1500 on the bars and 2300 lumen on the helmet ) unless I'm going downhill or riding over a lot of technical features.

  4. #4
    EAT MORE GRIME
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    note never try to charge one if you've been in the cold like 32 deg or lower and the batteries are still cold

    coming in from a cold ride ?
    let it warm up to room temp (or at least 50 deg) before connecting charger for best expectation of battery life for lithium cells.
    "Put your seatbelt back on or get out and sit in the middle of that circle of death." - Johnny Scoot

  5. #5
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    Supposedly a big culprit in how long the batteries will last is the voltage level they are stored at when not in use (as mentioned by Cat above). Andy is right - the number of charge cycles is #1, but 500 charge cycles is probably way more than enough for most of us (i.e. other factors will play in sooner).

    I just recently did a discharge test on my hobby charger (complete with graphs) on my two most used cells - LG MJ1's which I bought new Noember 2015. I haven't used the cells a ton, they did sit a lot, and generally fully charged. Well my discharge test surprised me by showing they are still performing very very well! I wish I had discharge graphs to compare to when they were new (all I have are the graphs posted by HKJ).

    One thing that will definitely play in on battery "packs" is cell balance. Many times packs lose runtime simply because the cells have gone out of balance. You can check with a voltmeter and even rig up a rather simple way to re-balance them (if you don't mind opening up the wrapping/case). One quick way to check for cell imbalance is to check the voltage at the DC plug after the charger indicates charging is done. Do you get 8.40v or thereabouts? (Of course it would be best to know what voltage your charger usually shows complete charge at - not all will stop at 8.40v.) If you are significantly lower than 8.40v, I'd suspect cell imbalance.

    -Garry
    "My Bike Lights" Thread on BLF teardowns, measurements, and beamshots. Moving my photos, PM or post up if you can't see them.

  6. #6
    Doesntplaywellwithmorons!
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    The charging of freezing batteries is in particular a Lithium Ion and Lithium Polymer battery chemistry issue. If you want to experience fires and explosions, by all means try and charge them if they're below 0C/32F.
    I don't post to generate business for myself or make like I'm better than sliced bread

  7. #7
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    Yes, by all means ( as was said above ) try not to recharge your batteries immediately after a ride unless you plan to ride the next day. Storing Li-ions cells with less than a full charge is better for extending the life of your battery pack. Even though I tell people this stuff all the time I rarely do it myself. Then again I have a lot of batteries so trying to remember which are fully charged and which are not is not really something I can keep track of.

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