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Thread: 48v battery bank charged by 12 v charge controller

  1. Default 48v battery bank charged by 12 v charge controller

    Hey Everyone, obvious Newby here.
    I have 4 Kyocera 400 w panel system, still in the box.
    I also have 4 Deka 92AH 12v AGM batteries, that are supposed to be hooked up to a Cotec S1500 48v inverter.
    The charge controller that I have is a Sunsaver Duo controller, that is supposed to be able to charge two separate battery banks in the same time.
    The limitation is 12 v input on the controller, however I have two of the controllers, so theoretically I could charge all four batteries individually.
    My question is:
    Can I charge the 48 v battery bank (if I hook it up in series), with the Sunsaver duo (12v) charge controllers???
    I have double (post and screw type stud) terminals on the batteries, so I am thinking I could use the posts to get the series hook up and in the same time I could set up individual 12v charging coming from the controller on the screw type studs.

    I got the obvious answer, get a 48 v controller, however my geographical location makes it difficult to get parts, such as that, so I am keeping that as my last resort.

    Any input I most welcome.

  2. #2

    Default Re: 48v battery bank charged by 12 v charge controller

    Welcome to the forum.

    In my opinion this falls under the "not going to work" category. The (-) on the Sunsavers would be common to each battery, whereas the 48 Volt bank the second battery's (-) is connected to the first battery's (+) - a dead short across one output. You'd have to break the 48 Volt series connections to charge the batteries individually, and that's not very practical is it?
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

  3. #3
    Join Date
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    SF Bay Area (California)
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    Default Re: 48v battery bank charged by 12 v charge controller

    No--I do not believe you cannot connect a single SunSaver Duo to charge a "24" volt battery bank.

    The SunSaver would "assume" that both batteries share a common ground point (i.e., each battery can only be +12 volts above the common ground).

    You could take 4 independent 12 volt charge controllers (each connected to their own solar panel/array--electrically isolated from each other) and charge each 12 volt battery.

    Another issue may be--Many charge controllers assume that Ground is connected to the negative battery lead (for safety). In this case, each controller would have its negative connection connected to a different 12 volt battery negative terminal. So, it would be possible that the charge controller cases will be energized at 0, 12, and 36 volts with respect to ground. So you would need to make sure that none of the controllers touch each other, share common wiring (such as local digital/switch controls), and each has a completely separate solar array. Make sure that the controllers (and their connections) are not touchable by people in the room (say a shovel is laid against a couple controllers).

    The safety issues can be a huge issue here. Giving a "generic answer" is difficult because each vendor can "do its own thing" for grounding/interconnects.

    I don't know if the controller chassis is ground referenced or not--You will need to check and figure out your own setup for safety. Even fuses become an issue too (normally we only fuse/breaker the +/hot leads--for these controllers, even the negative leads will be "hot").

    If you have lightning in your region--this (using 4x 12 volt solar charge controllers) makes standard lightning grounding/protection/grounding techniques virtually impossible.

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

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