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How many batteries?

Discussion in 'Home Power and Microgeneration' started by Michael Shaffer, Jan 2, 2005.

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  1. I want to power a 1650 watt Metal Halide bulb off of an inverter,
    approximately how many deep cycle "car batteries" would I need to power
    it for 30 minutes?

  2. You really don't want to use car batteries in this application, that's
    on the order of 150 amps. I'd use a couple of golf cart batteries in
    series, that'll last more than a couple of cycles, which is about all
    you'd get out of car batteries.
  3. Steve Spence

    Steve Spence Guest

    The answer, regardless of battery type is 14 amps at 120 vac, or 140
    amps at 12 vdc, so 30 minutes would effectively need 2 70ah batteries
    for 50% DOD.

    Reality suggests Two 27dc-6 deep cycle 115ah batteries from walmart at
    $53 each, and a 2500 watt inverter from BJ's at $269.

    How are you going to recharge the batteries?

    Steve Spence
    Dir., Green Trust
  4. Bill Darden

    Bill Darden Guest

    Hi Michael,

    You have asked a simple question that requires a complex answer. The
    simple answer is a lot.

    Please see Section 7.9 in the Car and Deep Cycle Battery FAQ on on how to size the batteries, inverter and charger
    for your application. By "car batteries", I assume you are talking
    about the physical size and weight, e.g., Group 24 or 27 because you
    should use deep cycle batteries for much longer battery service life.
    The most important conversion is the 1650 watts (12.1 amps) at 120 VAC
    to 145 to 169 amps at 12 VDC, depending on the efficiency of the
    inverter and loss. You might need to increase the battery capacity
    due to a lower temperatures, higher current rate due the Peukert
    Effect, and Depth-of-Discharge based on battery type.

    Kindest regards,

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