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Thread: Solar system to charge 24v and 12v batteries

  1. #1
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    Default Solar system to charge 24v and 12v batteries

    In my campervan I have 2 solar array arrangements.

    Both charge my 12v house batteries.
    One system is a 24v array, 500w MPPT controller.
    Second system is 12v array, 250 watt MPPT controller.

    Is it possible to connect an additional PWM controller directly to the 2v array and the 24v start batteries to keep them on float charge.

    I have tried a succession of buck/boost chargers on the 12v array, but they have not been up to the job.

    With thanks.

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  • #2
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    You would need to boost the 12V system to 27.6V (or whatever the float voltage of your batteries are specified), no need for another battery controller if this is just for floating. You just need to see that the step up voltage convertor (boost circuit) is up the to required amperage when the battery is low.

    This step up converter should be up to the job for the 12V 250W system:

    You set the output voltage to 27.6V before you connect it to the battery and then limit the current with the current adjuster to match the power of your panels. To do this you then connect the batteries which should not be fully charged(still in the bulk phase) and measure the voltage of the panels while you adjust the current limiter and when it is around 17-18V on the panels you got the right setting. Never mind if the output voltage on the battery is lower at that moment, it wll eventually reach the required floating voltage when the battery is charged. I would also disconnect the other 24V system from the battery when you do this setting.

    This is done normally of course when it is reasonably sunny but for some reserve I would not do the adjustment in the midday sun. Maybe at 10:00 or 14:00.

    You should have an additional proper solar charger to fully charge and equalise the batteries occasionally, which I assume comes from the 24V system.
    Last edited by nomeat; 18-05-18 at 12:08 AM.
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