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Thread: Powerex Maha C9000 Charger: Question about extremely concerning "Break-In" numbers.

  1. #1

    Exclamation Powerex Maha C9000 Charger: Question about extremely concerning "Break-In" numbers.

    Hello everyone. I have been looking around google for the answer to this, but I am not having any luck getting the exact info I need. I figured I would just ask here and see if you guys know what's going on.

    I just bought a Maha C9000 and a new pack of Eneloop Pro AA (rated at 2500 mAh)

    I did a full discharge first (just to be safe at a setting of 800 which is about 1/3 of total). That all went perfect as expected.

    I then started the break-in procedure. The Maha C9000 defaults to 2500 mAh (which is exactly the rating of my cells) so I just hit enter and set up the program.

    Everything was going fine last night until this morning when I looked at the readout on all 4 batteries and the number said they received 3950 mAh (and it was still going up)? I kinda freaked. I immediately touched the batteries to make sure they are not about to catch fire. They felt a lil bit warm, but not hot.

    This was only the first charge in the break-in procedure, before the discharge and 2nd and final recharge. Does that readout indicate these batteries took 4k mA when they are only rated for 2500 mA? Did I just ruin my cells? Did I make a mistake by setting it to 2500 mAh at break-in...should I have set it to 1200 mAh (about 50%) like you do for charge? Is my Maha 9000 defective?

    I just very well may not understand the readout figures and I'm getting alarmed over nothing (Which is what I am hoping for). However, at this point I am ruling nothing out. I assumed I would wake up and see 2500 mAh as the cut off point and then it should stop, rest and begin the discharge cycle. I didn't expect to see it blow way past the 2500 mark.

    Since it was not burning hot, I just kept a close eye on it and it is now on its discharge cycle. I have no clue though the danger I am running here (especially during the final recharge cycle tonight). I fear about starting a fire with this thing while I sleep tonight. If anyone can let me know that this is normal it would put my mind at ease. Right now I am tempted to abort the mission for safety concerns.

    Thanks in advance for any and all assistance.
    Last edited by Woots; 12-12-2017 at 03:46 PM. Reason: Typo

  2. #2

    Default Re: Powerex Maha C9000 Charger: Question about extremely concerning "Break-In" number

    Calm down, everything works fine. Break-in aims to deliberately put in the battery 1.6 times its capacity with 0.1C charge (250mA in this case). So, 2500mAh you set * 1.6 = 4000mAh so the procedure is about to finish - it needs 16 hours to do this break-in charging part. Having said that, eneloops practically don't need break-in, but it is good to determine the capacity.
    Last edited by apagogeas; 12-12-2017 at 02:56 PM.

  3. #3

    Default Re: Powerex Maha C9000 Charger: Question about extremely concerning "Break-In" number

    Quote Originally Posted by apagogeas View Post
    Calm down, everything works fine. Break-in aims to deliberately put in the battery 1.6 times its capacity with 0.1C charge (250mA in this case). So, 2500mAh you set * 1.6 = 4000mAh so the procedure is about to finish - it needs 16 hours to do this break-in charging part. Having said that, eneloops practically don't need break-in, but it is good to determine the capacity.
    Thank you for getting back to me and putting my mind at ease!

    I didn't realize you could charge that far over capacity if you trickle charge it (not sure if trickle charge applies to the non car battery world. The chemistry is different, but the end results are similar).

  4. #4
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    Default Re: Powerex Maha C9000 Charger: Question about extremely concerning "Break-In" number

    Yep it's fine.

  5. #5

    Default Re: Powerex Maha C9000 Charger: Question about extremely concerning "Break-In" number

    Break in mode is a very special case, but in general, the charge efficiency of a battery is not 100%, and we always have to put back some more than we took out. Some say NiMH is 70% to 90% charge efficient, others have said 70% to 100%, but I don't know what case that might be.

  6. #6

    Default Re: Powerex Maha C9000 Charger: Question about extremely concerning "Break-In" number

    The numbers you see on the charger are not what the battery is receiving. There are losses. For example, some of the energy is lost as heat. Powerex explains that in the instructions provided with the charger. When all else fails read the instructions.

  7. #7

    Default Re: Powerex Maha C9000 Charger: Question about extremely concerning "Break-In" number

    Quote Originally Posted by Lumencrazy View Post
    The numbers you see on the charger are not what the battery is receiving. There are losses. For example, some of the energy is lost as heat. Powerex explains that in the instructions provided with the charger. When all else fails read the instructions.
    All of the above, plus the fact, as far as I've come to understand it, that with a 0.1C charge the NiMH cell won't take offense of the over charge at all. Some have even said that you don't even have to discharge first. I've always discharged first, myself, but I have a hunch it's not needed either going by comments on forums, as long as the rate is low enough.

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