24 volt to 12 volt

3505740
3505740 Registered Users Posts: 2
in Wind Power Generation #1
Can a 24 volt wind generator and controller be used to charge a 12 volt battery? If not, how could I get it down to 12 volts to make it work? Thanks!
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,654 admin
    #2
    Re: 24 volt to 12 volt

    It all depends...

    Yes, you can directly charge a battery bank with a "24 volt" alternator--But you may lose upwards of 50% of the output energy:
    • Power = Volts * Current
    • Power = 14 volts * 10 amps = 140 watts
    • Power = 28 volts * 10 amps = 280 watts

    There are down converting MPPT controllers which can work with Wind (Midnite Classic for Wind) very nicely... But they are not cheap.

    A pure 24 volt charge controller that does not have a "12 volt" mode... No, it will not work.

    You do have the option of installing a 24 volt battery bank and use some sort of down converter (24 to 12 down converter, 24/12 battery balancing system used for buses and trucks with 24 volt starter batteries and 12 volt house loads, and even an MPPT solar charge controller connected to the 24 volt battery bank used to charge a second 12 volt battery bank). Again, not cheap, adds a second battery bank, etc...

    Good link about voltage conversions.

    And there are 24 to 12 volt DC converters (good for smaller loads like electronics and lighting). Still adds costs and larger DC converters are going to be expensive. May add electrical noise/interference for HAM and other Transceivers and Receivers.

    So--What are the 12 volt loads you are thinking of supporting?

    In many cases, you may want to skip the whole 24 to 12 volt down conversion and instead go with a 24 volt to 120 VAC inverter to power all of your loads. In many cases, this is not a bad way to go.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #3
    Re: 24 volt to 12 volt
    3505740 wrote: »
    Can a 24 volt wind generator and controller be used to charge a 12 volt battery? If not, how could I get it down to 12 volts to make it work? Thanks!
    You cannot use a 24 volt controller to charge a 12 volt battery bank. You can use it to charge two identical 12 volt batteries in series.

    There are two other ways you can deal with this:

    1. Replace the charge controller with a PWM charge controller designed for a 12 volt battery but able to accept the higher output voltage of a 24-volt designed generator. This will waste half or more of your power, so not a good idea.
    2. As above, but use an MPPT charge controller designed for a 12 volt battery and able to accept the higher output voltage. The MPPT charge controller will convert the higher voltage lower current to lower voltage higher current with tolerable efficiency.

    Neither of the above will necessarily work if the existing charge controller is integrated into the control system of the generator to the point that its exact behavior is required for safe operation of the wind generator.
    SMA SB 3000, old BP panels.
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  • 3505740
    3505740 Registered Users Posts: 2
    #4
    Re: 24 volt to 12 volt

    Those two posts told me all I needed to know. Thanks!
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  • Brianellul
    Brianellul Solar Expert Posts: 95 ✭✭
    #5
    Re: 24 volt to 12 volt
    3505740 wrote: »
    Those two posts told me all I needed to know. Thanks!

    Hi

    As others already told you, if the controller is integrated into the control system of the generator, then no it can't be done, however I managed to convert my 24v Air-X marine to charge both 12v and 24v batteries, depending on the wind speed / turbine output as described here. It's not perfect and complex but it works OK.

    Regards
    Brian
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