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Reverse battery polarity?

divayv Posted messages 312 Status Member -  
 kronos -
Hello everyone

I am trying to reverse the polarities of 2 Li-ion batteries of 3.6 V in parallel that have accidentally been reversed, but I am unable to do so. What should I do? Thank you for your help :)

PS: here is the long version for history enthusiasts :) :

I have an ACER laptop, but I've been having a battery issue for some time. After formatting the disk by the technician, I don't know exactly what he did, but now I find a "dead" battery, as it shows the famous "plugged in, not charging" when I try to charge it in Windows 7. If I unplug it, it just cuts off even with the battery! I've done some research and discovered that this could be due to an inversion of the battery polarities. Being curious by nature, I decided to open the battery (yes, I know it’s very dangerous and I shouldn't have, but what's done is done and I didn't come here to hear reprimands ;-)). As I expected, I find 3 "packs" in series of 2 Li-ion batteries in parallel of 3.6 V each, totaling 10.8 V. The first one is charged to 0.5 V, the second to 2.5 V, and the third to -0.3 V! Thinking that the issue was with this last pack, I decided to recharge it first with 1.2 V and then with 3.6 V, but nothing works: I can't get those -0.3 V to budge! Anyway, I don’t know what else to do, which is why I'm asking for a little help from the community. Thank you :)

3 answers

  1.
    TheBledard Posted messages 5234 Registration date   Status Contributor Last intervention   1 476
     
    Once the polarity is reversed, it cannot be reversed again. It's an irreversible material damage.

    The polarity reverses when the battery is completely discharged (it goes below 10%).

    --
    TheBledard
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    1. TheBledard Posted messages 5234 Registration date   Status Contributor Last intervention   1 476
       
      The theoretical 10% limit, according to the OS. In reality, the remaining charge is even less significant.
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    2. Edem
       
      Thank you.
      0
    3. Tml
       

      What are the risks associated with using the battery in reverse polarity,

      0
  2. divayv Posted messages 312 Status Member 22
     
    If I try to completely empty it (0V) and then recharge it from there, is it possible?
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    1. TheBledard Posted messages 5234 Registration date   Status Contributor Last intervention   1 476
       
      Exactly, the polarity changes after complete discharge. It no longer recharges because the charging system thinks it is connected the wrong way around.
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    2. divayv Posted messages 312 Status Member 22
       
      That's exactly why I decided to open the battery and "manually" recharge the cells directly at their terminals without going through the circuit board. But nothing works, the -0.3V remains.
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  3. divayv Posted messages 312 Status Member 22
     
    I noticed that I finally managed to recover the other two groups of batteries, including the one at 0.5 V, which I charged to 3.2 V simply with 3 batteries in series. However, I still can't do it with those at -0.3 V. I thought that maybe trying with a higher voltage (like 12V) might work, but I'm not sure about the risks, so I prefer to avoid it. I also considered simply reversing the connections (the batteries would end up in the right direction), but since the anode is graphite and the cathode is cobalt (or manganese), I assume there's a reason for that, and I’m also uncertain about the dangers involved. Thank you for shedding some light on this! :)
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    1. mariam-j Posted messages 50 Registration date   Status Member Last intervention   34
       

      HELLO,
      As far as I know, to repolarize you need a much higher voltage (24; 48 V or even more), and to act by impulses.

      -1
    2. kronos
       

      Hello

      A significant known risk is explosion. Hydrogen production that in the right proportions with the oxygen in the air can create a detonable or deflagrating mixture.

      The presence of electricity and the risk of sparks when handling batteries increases the risk.

      The heating during normal charging increases the risk to the point that the temperature is normally monitored to interrupt the charging in time.

      I don't know how to reverse a negative voltage, but one method to "recover" rechargeable batteries is indeed to charge them one by one to achieve maximum charge levels by replacing those that are completely empty and no longer accept charge.

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