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What would you do?

Discussion in 'Fred's House of Pancakes' started by ny_rob, Jul 24, 2013.

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  1. JMD

    JMD 2012 Prius 4 Solar Roof

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    #21 JMD, Jul 25, 2013
  2. FL_Prius_Driver

    FL_Prius_Driver Senior Member

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    Don't assume the boom box is innocent in all this. One of the things that can cause NiMh to go bad is when leakage currents (or the Power Switch left ON) allows the batteries to discharge close to zero volts. Then the batteries with some charge left can put a reverse polarity on the remaining batteries. This does very bad things to those batteries reaching zero first. No matter what you do, always store rechargeable batteries individually, and fully charged if possible.
     
    #22 FL_Prius_Driver, Jul 25, 2013
    fuzzy1 and massparanoia like this.
  3. Mr Incredible

    Mr Incredible Chance favors the prepared mind.

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    I would throw it all out and go to Walmart to get a regular setup. The ones I use have been recharged numerous times with no ill effects.

    Or, use regular batteries.
     
    #23 Mr Incredible, Jul 26, 2013
  4. ny_rob

    ny_rob Senior Member

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    Well, I ended up "jump starting" the 6 "Bad" batteries with a small variable 0-6 volt DC power supply I had made a few years back.
    When I checked the "bad" batts on the DVM last night they showed 0.1 volts- so I set the power supply to 1.25 volts- and held it's pos and neg leads to the battery directly with the DVM connected the whole time. Initially I could hear the power supply load down- but I could see the battery voltage slowly start to climb. It started off at .3 volts- then within about 90 seconds it climbed to 1.1 volts at which point I disconnected the battery from the power supply. I did that with all 6 "bad" batts. After that I loaded them (4x at a time) into the smart charger- and now they started charging!
    One set had been in since 8pm last night- they typically take 10-14hrs to charge up and was fully charged this morning. When I put the remaining 2 batts in the charger this morning- they showed up as "Bad" again- guess they didn't hold the 90 second "jump start" charge from last night, so I gave them both another 90 second charge straight from the power supply- then popped them directly in the smart charger- and they also started to charge normally again. Once all six have charged- I'll exercise them a few cycles.

    So it looks like all six "bad" cells have been revived by "jump starting" them directly from a DC power supply.
    Somehow I can't see Joe-six-pack consumer doing that with supposedly "bad" batteries.
     
    #24 ny_rob, Jul 26, 2013
  5. rcf@eventide.com

    [email protected] Member

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    Feeling experimental? Don't have a power supply? Once you've charged the "good" battery, connect it in parallel with one of the "bad" ones for a few minutes and then put them both back in the charger. Maybe the charger will change its mind about the "bad" one.
    Richard
     
    #25 [email protected], Jul 26, 2013
  6. ny_rob

    ny_rob Senior Member

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    That was my backup plan if I couldn't find the old 0-6 vdc power supply.
    Although I was a bit concerned that connecting one of the bad batts in parallel to a fully charged one would be almost like a short on the good battery. Luckily I was able to locate the power supply.

    Going forward- I do have an internet radio that I use daily (with 4x LSD rechargeable "D"'s)- so I guess I could just keep these 8 "D"s out of the boombox that I hardly ever use and rotate them through the internet radio to help keep them fresh.
     
    #26 ny_rob, Jul 26, 2013
  7. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    Awesome, less batteries at the landfill!

    Just keep in mind that how you charged it was probably not the best. You charged it with a constant voltage from a 1.25v source. You could hear the supply loading down, and that was the only current limiter. This is bad for batteries and explosive for some chemistries. You really need a proper power supply with both voltage and current knobs. Set the current limit in the milliamp range, voltage to 1.25 and then let it charge up slowly.

    Glad it works, but do be careful in the future if you want to "jump" them again.
     
    #27 2k1Toaster, Jul 26, 2013
  8. ny_rob

    ny_rob Senior Member

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    Agreed- it was pretty much my last resort to bring them back to life.
    I had a 12v car battery blow up in front of me when I was a kid- so I'm not keen on having it happen again.
    The small DC power supply was limited to the 1000 mAh input that it's wall-wart ac transformer supplies.
    I was very concerned about my method- that's why I kept the DVM connected to the power supply leads the whole time and I was closely monitoring the voltage (and battery temperature) during the jump start - as soon as it got up to 1.1 vdc I disconnected the battery from the supply. It seemed like a good voltage number- the battery never got warm and it was enough to get the smart charger to start charging again.
    If it was inexpensive "AA" batts- I probably would have just chucked them- but at $7 per battery for the "D"s it was worth trying.
     
    #28 ny_rob, Jul 26, 2013
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