Battery voltaje drop

Discussion in 'General Electronics Chat' started by Iodem_Asakura, May 20, 2005.

  1. Iodem_Asakura

    Thread Starter Senior Member

    Sep 14, 2004
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    0
    I have seen sometimes the voltage of a battery to go down slowly when it is supplying power, but at some moment fall down greatly fast (like a jump), beign the consumption the same.

    Why this happen? In my laptop, sometimes the battery read 30% (and discharging, of course) and instantly drop at about 4%. And happen being the consumption the same.
     
  2. David Bridgen

    Senior Member

    Feb 10, 2005
    278
    0
    Many rechargeable batteries exhibit behaviour like this. The voltage when fully charged is only slightly higher than the voltage when almost discharged. Once the voltage starts to drop significantly (and rapidly) the discharge should stop, otherwise you run the risk of one or more cells becomning reverse charged.
     
  3. Iodem_Asakura

    Thread Starter Senior Member

    Sep 14, 2004
    140
    0
    Ok, but i can't understand why the jump in the voltage level. I thought the voltage should go down practically at the same rate if i'm consuming the same power, but in theses cases the voltage begin to drop slowly and in some moment it make a jump.

    I shoul clarify the cases i have seen this the battery in question are not in good conditions, they work, but they're old. I haven't noticed this behaviour in new-good state batteries.
     
  4. David Bridgen

    Senior Member

    Feb 10, 2005
    278
    0
    I would think, then, that one or more cells in these batteries have less capacity than the others. During discharge the voltage of this/these cells will drop very rapidly to zero once they are exhausted, and will start to be charged in reverse by the current through them from the remaining good ones.

    In the case of NiCd cells it is possible to rescue and rehabilitate them if you have a bit of time and patience. I guess it would be possible with other types too, but I have no experience of doing so.
     
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