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Solarex MSX-83 series or parallel

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  • Solarex MSX-83 series or parallel

    Hi, I have two of the above panels charging 2x 12 volt batteries in parallel running a 12 volt water pump. I have been only using one panel as the small controller I have is only 5 amp. I now have a 20 amp PWM controller. Really cheap one(picture attached. Would it be best to series or parallel the two panels. They are 17.1 volt and 83 watt each. I expect parallel is best as the 17.1 volts is plenty to charge a 12 volt battery system.
    Thanks,
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  • #2
    Originally posted by asdex View Post
    Hi, I have two of the above panels charging 2x 12 volt batteries in parallel running a 12 volt water pump. I have been only using one panel as the small controller I have is only 5 amp. I now have a 20 amp PWM controller. Really cheap one(picture attached. Would it be best to series or parallel the two panels. They are 17.1 volt and 83 watt each. I expect parallel is best as the 17.1 volts is plenty to charge a 12 volt battery system.
    Thanks,
    When you have a PWM controller, there is not point in raising the panel string voltage above the minimum needed to charge whatever battery voltage you are using.
    For a 12 battery or battery pack, and a PWM controller, you want a panel Vmp in the range of 18V. Anything more would be wasted, as the current to the battery would be almost exactly the same as with only one panel.

    By all means, put them in parallel. And with only to panels you will not need to put a separate fuse on each one.
    But what size are your batteries? If you have, for example, two 100AH 12V batteries, then you have a 200AH system and your batteries would be best charged by at least 300 total watts of panels, given the inevitable inefficiency in the PWM control method.
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

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    • #3
      Originally posted by inetdog View Post
      When you have a PWM controller, there is not point in raising the panel string voltage above the minimum needed to charge whatever battery voltage you are using.
      For a 12 battery or battery pack, and a PWM controller, you want a panel Vmp in the range of 18V. Anything more would be wasted, as the current to the battery would be almost exactly the same as with only one panel.

      By all means, put them in parallel. And with only two panels you will not need to put a separate fuse on each one.
      But what size are your batteries? If you have, for example, two 100AH 12V batteries, then you have a 200AH system and your batteries would be best charged by at least 300 total watts of panels, given the inevitable inefficiency in the PWM control method.
      Thanks, I'll check the battery size this weekend when I'm there as I can't remember offhand. The are secondhand seal batteries I got from work. Probably around 60 AH each but will confirm. Thanks,

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      • #4
        Hi, checked the batteries and are 90AH. They are not in great condition and one was getting hot so I disconnected it. I pumped the water when the sun was high and it went ok although the pump revs dropped a lot when the new controller pulsed. I'll need to get a new battery. The pump draws about 9 amps for 20 minutes every two days.
        Cheers,

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