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Battery in parallel

  1. Jun 14, 2013 #1


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    i know its not possible but isn't there any way in which two batteries of different capacities or voltages be connected in parallel ?
    Is there any way to limit the current in that case
    by using small value resistance to drop the current?
    or by adding a convertor from high to low current value or a control device?
    please let me know about it .
  2. jcsd
  3. Jun 14, 2013 #2

    Simon Bridge

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    Welcome to PF;
    Of course - just connect up the wires. (What do you mean "I know it isn't possible..."?

    You can treat the batteries exactly the same as you would a single battery.
    You aught to be able to see what happens in a mesh analysis.

    Note, however, that resistors are said to "drop voltage", not current.
    Perhaps you are concerned about the current flow between the unequal batteries?
  4. Jun 14, 2013 #3
    Hello SM .... Well agreed it is possible , but never practical to parallel batteries of different voltage, or really different types. This can actually be dangerious - if you effectivly start charign a battery that is not meant to be charged.

    The simple way is to use a diode on the output of each, that will prevent the higher voltage of one battery from charging the other. But if the battery voltages are low - you may not want the added voltage drop of a diode, or the losses.

    Beyond that it really will depend on the application.
  5. Jun 19, 2013 #4


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    Parallelling up batteries, willy-nilly, that are of different ages, conditions, types, capacities and states of charge can damage you or both batteries.
  6. Jun 19, 2013 #5


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    There is a type of battery isolator known as a shottky battery isolator, which is just basically uses diodes to prevent the batteries from charging / discharging one another. I work on komatsu 930-E electric drive trucks, they are used there. The battery bank is a set of four 12 volt batteries. Two in series in parallel with two more. They run through the battery isolator to prevent one set from charging the others in case one set loses its charge.

    but you shouldn't ever connect batteries of different capacities/voltages it is just used as a safe guard.
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