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Thread: Refresh/discharge/restoration of batteries

  1. #1
    Flashaholic*
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    Default Refresh/discharge/restoration of batteries

    Hello,

    Can someone tell me what's the difference between refreshing/discharge/restoration of batteries?

    Do you do those to your batteries?
    Is it good for li-ion, IMR, lifep04, and nimh?

    Should I get a charger that has those features?

    Thanks.

  2. #2
    Flashaholic* mattheww50's Avatar
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    Default Re: Refresh/discharge/restoration of batteries

    The only batteries it makes any sense to refresh/restore are NiCd and possibly NiMh. The only thing you will do with Lithium cells is use up life. With NiCd if they are stored for long periods of time, or they are repeatedly only partial discharged, it is possible for the micro-crystaline structure of the chemistry to aggregate into much larger crystals, greatly reducing the surface area available. So while the actual total capacity remains the same, the usable capacity can drop dramatically because the available surface area is main factor in internal resistance. One you reach the usual discharge point, the sudden decrease in surface area cause a large increase in internal resistance, giving the appearance that the battery is discharged. It is only by fully discharging a cell with this problem,and then re-charging that the problem can be rectified. In addition, many NiCd and NiMh need a certain amount of 'break-in' to reach full capacity. These are issues that are quite specific to NiCd and NiMh batteries. The only thing these features are potentially useful for with Lithium cells is measuring actual capacity, there is nothing to be gained for doing so in terms of cell capacity, but Lithium cells generally are good for many fewer cycles than NiMh or NiCd cells, so you end up using up lifetime when you use this feature. In short, these features are generally only useful if you plan to use NiCd or NiMh cells.

  3. #3
    Honorary Aussie
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    Default Re: Refresh/discharge/restoration of batteries

    Great info on the differences, thanks.

    I ran into a situation where the NiCd actually still made sense (please correct me if Iím wrong). This had to do with some old walk way lights, which turned out to have NiCd batteries. Since theyíre not that sensitive to being overcharged, and during the summer at our latitude we can get 17 hours or so of sunlight, the NiCd batteries are actually not a bad choice.
    Last edited by magellan; 10-18-2018 at 07:57 PM.
    It is better to buy a beautiful, expensive, custom flashlight than to curse the darkness.

  4. #4
    Flashaholic* mattheww50's Avatar
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    Default Re: Refresh/discharge/restoration of batteries

    There are actually a few places where NiCd's still make some sense. They are indeed very tolerant of overcharging. They can also take enormous abuse. They are also commonly used on light gas turbine powered aircraft. An 80 lbs 24V NiCd is used to start at PT6 gas turbine. It takes about 700 amps initially. As soon as the first engine is started, it is then recharged at about 250 amps for a minute or two, and in turn is used to start the second engine (which is much easier because the running engine can provide about 200 amps). These cells have incredibly low internal resistance, which allows them to deliver enormous numbers of amperes.

  5. #5
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    Default Re: Refresh/discharge/restoration of batteries

    I agree completely with Mattheww50, it depends on the chemistry. I have tried cycling quite a few LiIon cells, over 100 from old laptop pulls with no significant increase in capacity. Low self discharge NiMh cell like eneloops same thing, once the internal resistance starts to build up there is no saving them. Non LSD NiMh cells that have been sitting a long time, yes cycling does help from my experience. NiCdís are the shining star here, cycling can work wonders for them. I have seen this first hand. I think it has to do with LiIon and NiMh cells having a rated cycle life which is usually about double the actual cycle life. But NiCdís in theory can be cycled indefinitely. I read an article from a link on this board that someone cycled some NiCdís over 2000 times with no decrease in capacity or increase in IR at all and then just due to lack of endurance of the testers they stopped. Owning a charger that can discharge to test capacity to me is a must have.

    Frank

  6. #6
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    Default Re: Refresh/discharge/restoration of batteries

    Thanks guys, really appreciate it.

  7. #7
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    Default Re: Refresh/discharge/restoration of batteries

    Quote Originally Posted by mattheww50 View Post
    There are actually a few places where NiCd's still make some sense. They are indeed very tolerant of overcharging. They can also take enormous abuse. They are also commonly used on light gas turbine powered aircraft. An 80 lbs 24V NiCd is used to start at PT6 gas turbine. It takes about 700 amps initially. As soon as the first engine is started, it is then recharged at about 250 amps for a minute or two, and in turn is used to start the second engine (which is much easier because the running engine can provide about 200 amps). These cells have incredibly low internal resistance, which allows them to deliver enormous numbers of amperes.
    For sure NiCdís donít get much love here.
    I have a bunch of Tenergy NiCd AAís that are rated at 1000mAh, in reality they should be rated a lot higher. When I do a discharge test I typically get around 1300mAh. A regular Eneloop AA is rated at 1900mAh and from my experience you get very close to that. So the NiCdís have about 68% of the capacity that the NiMhís have. Now price, a good price for 12 AA Eneloops is about 31.50, a good price for 12 AA NiCd Tenergys is about 10.20. So NiMhís are about triple the price of NiCdís. When you talk about self discharge of course Eneloops are way better than NiCdís. Cycle life is the opposite, NiCdís blow away NiMhís. It comes down to how you answer these questions.
    Do you need 32% more capacity and willing to pay triple for that?
    Do you need low self discharge and willing to pay triple for that?
    Do you need to be able to just throw them in household trash a not recycle them and willing to pay triple for that?
    If you answer NO to all of the above consider NiCdís.
    Frank

  8. #8

    Default Re: Refresh/discharge/restoration of batteries

    Slightly OT -- I have some Duracell AA Nimh "stay charged" that I think are 1500 mAh, but I can't find them anymore.
    All I see are the "Rechargable 2400 mAh" type.
    Of course, maybe the 2400 mAh give equivalent shelf life to the LSD that tops off at 1500 ???
    I want LSD for lights that are not used very often, and electronic controllers.

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