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Does volts and amps get at half while charging multiple batteries?

  1. Aug 14, 2012 #1
    Hi guys (and gals)

    Say, i have a solar panel rated at 100w 12v with the following specs:

    Short circult current(Isc): 6.01A
    Open circuit voltage(Voc): 21.5V
    Optimum operating current: (Imp) 5.52A
    Optimum operating voltage: (Vmp) 17.78v
    Maximum power: (Pmax) 100W

    And I decide to charge two 50ah batteries (each), from full discharged both, Does that mean that the voltage or amps will be split to half? (for each battery) or will both batteries receive the same (maximum) voltage and amp as if i was just charging one single battery with the same solar panel?

    Also, if this panel is charging batteries or a battery, what's the maximum power it will be delivering (while providing energy) 17.78v? or 12v? or 21.5v? or what?
    What for the amps too?

    Gracias a lot.
  2. jcsd
  3. Aug 15, 2012 #2


    User Avatar

    Staff: Mentor

    If you have two batteries, identical in all respects, and you charge them as a parallel pair, then each will get half of the current from the solar panel. Each will get the full voltage. HOWEVER, as your batteries will never be identical, it is not a good idea to simply parallel them.

    At 17.78v your panel, under the ideal conditions that the manufacturer tested it, can deliver 5.52A.
    Power = V·I
    At 12v expect to get fractionally more than 5.5A, maybe 5.8A.
    At 21.5v you can't draw much current at all, that is the open-circuit voltage; draw any current and the voltage will fall away.

    It is generally better to charge the batteries separately; the high cost & limited life of secondary batteries, compared with the cheap cost of electronics, means it is worth treating the batteries well.
    Last edited: Aug 15, 2012
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