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using solar panels to charge a UPS?

Discussion in 'Photovoltaics' started by Anonymous, Jan 16, 2011.

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  1. Anonymous

    Anonymous Guest

    A 4 kVA UPS was left behind by a tennant who moved out of
    an office we rented. It still works, but the batteries are
    3 years old, perhaps one foot in the grave.
    Now I wonder if I can use this to make a stand-alone solar power
    system (not tied to grid) for a holiday house.
    This would only have modest power requirements < 2500 W a few hours
    per day. It is in a sunny locale 32 degrees from equator.
    The UPS has batteries wired in series for 48 V DC, so I could use
    two truck batteries, instead of sealed gel batteries.
    I can get some Bosch panels for a good price. These have Vmpp 27 V
    which would be okay to charge battery, but Voc is 33 V.
    Would this be a problem?
     
  2. Bruce Gordon

    Bruce Gordon Guest

    Yep, but understand that UPSs are NOT designed for conversion
    efficiency like a GridTied inverter system. Their Inverter design is
    grossly inefficient because they are designed to provide instant Power,
    for a short duration, and then take a long time to recharge the
    batteries. You will need a "GOOD" MMTP Charge Controller, (Outbacks MX
    Series) to do the Solar to Battery voltage conversion to get 48 Vdc into
    the batteries.....
     
  3. Josepi

    Josepi Guest

    PV panels are constant current sources. You would have to find out the
    current output and see if the batteries can stand that current every day for
    about 4-5 hours.

    A Smart MMPT is the best charger, usually.


    A 4 kVA UPS was left behind by a tennant who moved out of
    an office we rented. It still works, but the batteries are
    3 years old, perhaps one foot in the grave.
    Now I wonder if I can use this to make a stand-alone solar power
    system (not tied to grid) for a holiday house.
    This would only have modest power requirements < 2500 W a few hours
    per day. It is in a sunny locale 32 degrees from equator.
    The UPS has batteries wired in series for 48 V DC, so I could use
    two truck batteries, instead of sealed gel batteries.
    I can get some Bosch panels for a good price. These have Vmpp 27 V
    which would be okay to charge battery, but Voc is 33 V.
    Would this be a problem?
     
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