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marininn's avatar
marininn
Explorer
Dec 21, 2016

batter charger drain?

I have a auto battery charger wired into the array. The 2-amp camper charger is just not enough to charge a battery, so I have a 10 amp hooked in.
My question, does current flow backwards through the DC side of the transformer and drain power?
When I turn the charger off I assume all it does it disconnect power to the AC side of the transformer.
If you know I would like to hear, if you don't then you don't so no comment needed.
  • RCMAN46's avatar
    RCMAN46
    Explorer
    Dec 22, 2016
    If it is a smart charger such as the Battery Tender it will discharge the battery if AC is removed.

    The smart chargers monitor the battery voltage with a small load on the battery.

    I had one run my battery completely down in a couple months due to a GFI outlet tripping.
  • MrWizard's avatar
    MrWizard
    Moderator
    Dec 22, 2016
    It takes rectifiers aka diodes to turn stepped down a.c. Into dc

    It's a one way circuit

    Think of like your car alternator, the alternator does not drain the car battery when parked, it's all the radio memory and other stuff
    The alternator has diodes that make dc from the ac
    Same thing in your battery charger
  • ScottG's avatar
    ScottG
    Nomad
    Dec 21, 2016
    marininn wrote:
    can you also elaborate? just for curiosity. What stops it?


    A diode bridge (4 diodes), which is primarily there to convert the AC to DC but needs addition components to do so cleanly.
    This is very similar to how your alternator works. In either case if any of those diodes fail it can cause the battery to then discharge backwards through the circuit.
  • Mandalay_Parr's avatar
    Mandalay_Parr
    Explorer
    Dec 21, 2016
    marininn wrote:
    can you also elaborate? just for curiosity. What stops it?


    In simple terms, they have a diode or switching transistor that only allows D.C. Current to flow one direction.
  • agwill's avatar
    agwill
    Explorer
    Dec 21, 2016
    Diodes/rectifiers allow current to only flow in one direction. So current will not flow into charger.
  • time2roll's avatar
    time2roll
    Nomad
    Dec 21, 2016
    Best to measure or check with the manufacturer.
    Generally it would be very low as a few milliamps max unless it had some special control system electronics to run.
    Might help to post exact model numbers.

    What is the concern? The 10 amp should not materially affect the 2 amp from maintaining the battery. Although typical RV idles at 1/4 amp to 2+ amps so best to be disconnected with a small maintainer.

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