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Lead Acid Battery Bulging

Discussion in 'Misc Electronics' started by Zach Zaborny, Jul 17, 2005.

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  1. Zach Zaborny

    Zach Zaborny Guest

    I have two 12v 10Ah lead acid batteries that an electric scooter runs on.
    I lost the original charger and have been trying to use a car battery
    charger I had laying around. When doing each battery individually, they
    charge normally. However, I tried doing both batteries (in parallel), one
    started "bulging." Also, the bulging battery was very hot after charging,
    which may be the cause of the bulging (plastic + high temps = not
    good.) But the other battery was fine.

    The charger is rated 8A @ 12/6V. It's built-in ammeter says that when
    I put both batteries on in parallel, only about 7A is drawn; if that helps.

    The charger is supposed to shut off when they are done charging, but
    they never "charge" until they no longer draw any current. The lowest
    the ammeter goes is 2A when they are on there. I have no idea if this is

    What's going on here?

  2. CWatters

    CWatters Guest

    Have the batteries been left empty for any length of time? That's the
    fastest way to kill lead acid batteries. If these are wet cells then it's
    best to leave them on a charger which has a float charge mode between use.

    I think I would be tempted to measure how each battery performs by
    discharging it to say 50% capacity using 12V bulbs. (eg draw 5A for 1 hour).
    If the voltage on one is much lower than the other while on discharge or
    gives out before it reaches 50% then it's probably suspect and due for
  3. Jamie

    Jamie Guest

    sounds like to me one of the batteries already had a good charge in it
    and was getting drained off very fast, or was getting charged very fast
    by the other etc..
    try using high amp Diodes to isolate them, your charger should have
    enough to get over the average .7 volt drop.
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