Battery connection

Discussion in 'General Electronics Chat' started by superway, Jun 20, 2011.

  1. superway

    Thread Starter Active Member

    Oct 19, 2009
    128
    0
    Hello,

    I have 2 batteries and each one rates 12vdc, 86Ah, and have another 2 batteries each one rate 12vdc, 108Ah. Is there any major issue if i connect them in parallel to test an Inverter Power Supply?

    Please help.

    Thanks

    ken
     
  2. #12

    Expert

    Nov 30, 2010
    16,283
    6,795
    The discharge cycle will be ok because the batteries will give lower voltage as they discharge, so the stronger batteries will lose voltage slower and tend to provide more current as they all slowly discharge.

    Still, keep an eye on their voltages so you don't run them completely flat. They tend to self destruct when you do that.

    Recharging is when you have to seperate the sizes to keep them safe.
     
  3. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    Unless they are in just the right state of charge, so that their terminal voltages are very similar, there is a very definite danger of large circulating currents if the two batteries are put in parallel.

    You need to be very careful about this.

    Edit: Three batteries! Perhaps I'm being a bit paranoid about this, but serious accidents have happened this way. For instance, if one of those batteries had a shorted cell...
     
    Last edited: Jun 20, 2011
  4. #12

    Expert

    Nov 30, 2010
    16,283
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    Oh...I assumed the batteries would all be in good condition and properly charged before the test. My bad.
     
  5. victorhugo289

    Member

    Aug 24, 2010
    49
    3
    I think there would be no problem if you use it for your test. If one of them would deplete faster than the others --which would happen after a while-- then there would be a problem because a battery in parallel which is not the same voltage as the others becomes a LOAD to the entire circuit drawing huge amounts of current. But this would happen after a while, I don't think you would have trouble if you use it for your test.
     
  6. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    If two batteries with different terminal voltages are connected in parallel, you can get into trouble straight away.

    I have seen this kind of accident, with bulging melted battery cases and horrid choking fumes stinking the place out. Two 48V batteries on the same circuit, one new and fully charged, the other nearly flat and probably with a dead cell or two, even before the boil-up. Luckily nobody was injured.
     
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