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Thread: Restoring a dead NiMH rechargeable battery

  1. #1
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    Default Restoring a dead NiMH rechargeable battery

    Good (insert time period of choice),
    I have the Ansmann Energy 16 charger. And assorted AccuEvolution Low Self Discharge NiMH rechargables



    I did my research and these products seemed to be the best for my needs. With the charger itself you can leave the batteries in the charger indefinitely and they will not over charge.

    For reasons that I am not going to get into the recharger was left unplugged with the batteries inserted. Now most of those batteries are showing up as faulty cells. I am assuming that they discharged too much and do not have enough of a residual charge for the charger to refresh and then charge them.

    Batteries that were previously charged and left out of the charger were able to recharge with no problem.

    My question is, do any of you knowledgeable folks know if it possible for me to revive the faulty cells so the charger will be able to refresh and charge them. I have a very basic knowledge of batteries(what you saw above is the most I got). I did some google searches and came up with stuff I did not understand. If any of you have a way and can break it down Barney style I would be grateful. I would rather not have to purchase new batteries.

    Thank you muchly
    Last edited by JoshuaNY; 11-10-2011 at 07:11 PM.
    Ka-chow! Joshua
    Sir Loin of Angus - Knights of the Maillard Table and Loyal Arkolyte
    3017er "Load it like you hate it"

  2. #2

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    A couple of the 3-star reviews at that Amazon link mention this charger reports errors when batteries are in deep discharge. One of those people bought a cheapie charger to kick start the process.
    If you don't have another charger, try putting the batteries in repeatedly. This might top up the batteries just enough for the charger to finally recognise them.
    Ray.

  3. #3
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    you can fix NiMH batteries with a welder or even an automotive battery charger.

    google "refresh NiMH battery", maybe put DeWalt in the search if you can't find it.
    -Ray
    Some may never live, but the crazy never die. -HST
    BOTOC Power!

  4. #4

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    Quote Originally Posted by xraygun View Post
    you can fix NiMH batteries with a welder or even an automotive battery charger.

    google "refresh NiMH battery", maybe put DeWalt in the search if you can't find it.
    X2, Works on my dewalt drill batteries. Not sure I would try zapping a 1.5 cell alone like that.
    D.J.

  5. #5
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    I've done it with AA cells. Just a quick zap.
    -Ray
    Some may never live, but the crazy never die. -HST
    BOTOC Power!

  6. #6

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    Starting them off with a cheap charger has worked for me, when an "intelligent" charger refused to co-operate. A few minutes on the cheapie should be enough. Zapping them with higher voltage sounds a bit drastic to me - and they could explode.

  7. #7
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    These batteries are probably still OK. I would go with the cheaper charger to get them jumped and then put them in the other one. Or use the almighty Xraygun method.

  8. #8
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    Whether or not you can restore these depends on their age. If they're still well under the 2 years lifetime (from manufacturing) they should be restorable. They're just flattened. If they're older, which you probably have no way of knowing, then maybe not.

    Maha makes battery chargers with a conditioning cycle that can often resurrect problem batteries. It basically cycles the battery several times, charging and discharging them. I find this doesn't really work on multi-cell batteries (i.e. 9V) where a single cell may be bad, but they do a good job on single cells. Maha doesn't even bother with this circuitry in their 9V chargers, though they do have a more modest feature. The Ansmann has some cool features, but is missing this one, though it will discharge bad batteries once. You've found a second strike against Ansmann that I wasn't aware of. Even the Maha has trouble with some batteries, and using a cheap charger to kick start it might work... for a while. I haven't seen a battery survive long after the Maha failed with it, nor would they charge completely. In cases where it does work, it pays to go through the conditioning cycle several times. In fact, it's recommended to condition the batteries once every month or two when used daily. But my experience is with AA and 9V. The damage in these cases is probably from build up on the terminals, and that should be reversible, theoretically. I think the smaller batteries just don't have enough leeway to undo the build up. So, basically, the way to restore them is to cycle them--charge and discharge several times--but you might not be able to completely reverse the "damage", particularly with smaller cells.

    For more info, check out The Battery FAQ

    Iiirc, you want to slow charge them, not jolt them. A jolt is kind of like chipping off a hunk of coating with a screwdriver. It might work, but you're better off trying to coax it gently and clean it up more consistently. So, definitely try a cheap slow charger first., then maybe a fast charger, and reserve the more destructive method for a last resort. It looks like you're using size D batteries, which I do believe are large enough to deal with a quick shock treatment. Size C are probably okay too, but probably not AA. A shock basically pokes a hole through the build up to allow current to flow through. (There's another, even more destructive mechanism, dealing with gases, which might be why they sometimes pop or explode when you do this.) But that damages the area. With the smaller diameter batteries, that hole just takes up too much of the surface area. The damage may be reversible, or not. So this doesn't work nearly as well on smaller batteries. Also, the shock might destroy a smaller battery in other ways, mostly thermodynamic, where a larger one might survive.

    The FAQ mentions some things you can do to prolong a battery. One thing I always did with batteries that were used in low discharge circuits (low current or where the device would power off when the current dropped a certain amount) was to occasionally use them in a device that needed heavy current and didn't cut off--to basically, use them hard and heavy (well, moderately anyway) once in a while. It prolongs their lifespan. The conditioning cycle does something similar, though it uses a relatively light current. A flashlight comes to mind.
    Last edited by SiBurning; 11-11-2011 at 07:46 AM.

  9. #9
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    I've been using this trick a long time, but if memory serves, the zapping with the 12 volts knocks the crystals or dendrites off that keep it from charging. This only works with regular or older NiMH and NiCads, DO NOT use for a newer generation lithium or anything that has a circuit built into it. You'll fry it.
    -Ray
    Some may never live, but the crazy never die. -HST
    BOTOC Power!

  10. #10
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    Try freezing them for 15 minutes. Put them in cold and see what happens. I've rescued several batteries this way.

  11. #11
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    Hey guys thanks for the info. I kept putting the batteries in and out of the charger a few times. About half of them started charging. I then bought a cheap charger and then put them back into my main charger and they were able to take a charge. Thanks guys, saves me a few bucks. I just wasnt getting the info I needed from google.
    Ka-chow! Joshua
    Sir Loin of Angus - Knights of the Maillard Table and Loyal Arkolyte
    3017er "Load it like you hate it"

  12. #12
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    Quote Originally Posted by JoshuaNY View Post
    Hey guys thanks for the info. I kept putting the batteries in and out of the charger a few times. About half of them started charging. I then bought a cheap charger and then put them back into my main charger and they were able to take a charge. Thanks guys, saves me a few bucks. I just wasnt getting the info I needed from google.
    The freezer trick didn't work?

  13. #13
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    I didn't see your post until I signed on tonight. I had already tried the other two things I spoke of and they worked. If I saw it, I would have tried it first before purchasing the cheap charger. If it happens again I will give it a try
    Ka-chow! Joshua
    Sir Loin of Angus - Knights of the Maillard Table and Loyal Arkolyte
    3017er "Load it like you hate it"

  14. #14
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    Quote Originally Posted by JoshuaNY View Post
    I didn't see your post until I signed on tonight. I had already tried the other two things I spoke of and they worked. If I saw it, I would have tried it first before purchasing the cheap charger. If it happens again I will give it a try
    Ahh, no worries. I found that solution when I had the same problem with SWMBO's cell battery. Of course, that's a Li-ion and not a NiMh. Either way, I'm glad you're all fixed up.

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