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Newbie, been collecting pieces and parts for awhile...

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  • Newbie, been collecting pieces and parts for awhile...

    I've been collecting pieces and parts for awhile, I am getting close to install , need expert advise I have accumulated 36-UPS12-300 Batteris and 20-Photowatt 1650 panels also a Coet full bldg UPS with Transformer and sine inverters if any of this is usuable....any information or advise appreciated, I understand these batteries are best used for backup system, so thats where we will start. Thanks in advance

  • #2
    With such a large install you're maybe better contacting a local installer or electrician. If each of those batteries is 78Ah, 12V and you have 36 of them. Then max you can have 4 in series to get to 48V, then you have to start paralleling which is not ideal. If you do 2 strings then I calculate 48V 156A battery bank, 3 strings goes to 234A and 4 strings to 312A. With 4 strings you've used 16 batteries, and you've 20 left over. Maybe someone else can recommend if 4 strings of 4 in parallel is even a good idea - I've generally read that 2 strings is max recommended.

    Total wattage of bank (4 strings of 4) = 48x312 = 14,976 watts. You don't want to go below 50% so 7,488 watts available. Calculate at least 85% of that - so around 6000W to use. If only 2 strings in parallel is advised then half that value.

    You'd also have to calculate the total output of the solar panels. How many in series can you have before the Voc passes that of the mppt charge controller? Then how many strings of panels you can have in series before the Amps exceeds that of the mppt charge controller. etc.


    • #3
      Read this topic on parallel batteries problems