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Charger controller

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  • Charger controller

    Hi guys, I presently own a 100 watts Noma solar panel and I want to change charger controller. I would like to have a controller that have different indicators output.
    next year I want to had a second 100 watts panel.
    What type should I look for. This is for my RV with a deep cycle battery. Another thing is I would used it with my present 100 watts for the balance of camping days.
    I 'm glad to be member of this forum. I'm looking for help

  • #2
    Hello Gillies 1945 and welcome to Solar Panel Talk

    Depending on what that 100 watt panel is rated I would get a charge controller that can handle at least 3 times the Imp rating. So for example if the Imp rating is 5.5 amps then you will need a CC around 16.5amps or maybe just go with a 20 amp PWM type CC.

    Remember a PWM type CC will lose about 33% of the panel wattage so once you go above 200 watts you might want to think about an MPPT type CC so you won't lose all that wattage to charge your battery.

    Also remember that your battery Ah rating determines the amount of charging amps. So with only a 100watt panel you are probably talking about a 55Ah 12V battery. But adding a second 100watt panel means your battery is about 110Ah. A good charge rate is between C/8 and C/12 where C = the battery Ah rating.

    What is your RV battery rated? That value should tell you how many charging amps you need to keep it happy. Too little and you can sulfate it and too many amps could end up boiling off the water.


    • #3
      I've been using a couple of Victron Smartsolar MPPT units and I'm really happy with them. The Smartsolar line has built-in Bluetooth so you can connect to it with a smart phone, tablet etc and see a lot of info such as history, charge current, etc. They don't have much in the way of front panel displays, however. The Bluesolar line is cheaper but doesn't have the built-in bluetooth radio. Without knowing the specs of your 100W panel I'd guess that the 100/30 would be about the right size, allowing up to three of those panels to be used in series or parallel (but I'd confirm first that your panel voltage is high enough for whatever controller you choose if using one panel, two or more in parallel).

      There are a lot of choices out there, this is just one that I'm using and happy with.
      Last edited by sdold; 10-04-2021, 12:38 PM.


      • #4
        I also have Victron SCCs. Victron makes a 75 volt series that is available in different amperage outputs. The 75/15 would be perfect for 200 watts of panels which could push 12 charging amps to the battery. There’s no indicators on the SCC. It is all Bluetooth. For me, I have some other things like a Inverter that has indicators that I can get up and look at, but who wants to do that when you can use Bluetooth from the phone?

        If you have a Larger RV, I was told a rule of thumb is two GOlf Cart Batteries and 300 watts of panels. SO for growth you might want to think about a 100 volt 20 amp or 30 amp SCC. That rule of thumb is what a few Boondockers I meet use, but 2 golf cart batteries won’t power a propane blower motor overnight on the coldest nights where the heat is going off all night.

        Just be have a good plan going in or be ready to replace parts.


        • #5
          Thank you guys, I bought a Renogy 30A. Like I said I have a Noma 100 watts can I pair it with a 100 watts Renogy ???


          • #6
            Originally posted by Gilles1945 View Post
            Thank you guys, I bought a Renogy 30A. Like I said I have a Noma 100 watts can I pair it with a 100 watts Renogy ???
            Probably can pair them. What are the VOC and VMP?


            • #7
              Thanks Christian,
              the VOC is 21.5 volts and the VMP is 17.1 volts
              regard Gilles


              • #8
                Is that the VOC for both panels? If so its no problem.

                Here’s a link with some math.


                THe 100 watt panels I looked at of different brands are so close in voltage, it makes an insignificant difference if hooked up. The caveat to that is some companies manufacture a “24 volt panel” which outputs between 30 and 33 volts that would not match well.

                If VMP is 17 though, and you have an MPPT controller, that gets to the point where it is “barely” meeting specs to run the MPPT. If that’s the case for the MPPT, put them in series of 2 and the problem is solved.
                Last edited by chrisski; 10-14-2021, 05:50 PM.


                • #9
                  Thanks Chrisski,
                  This is the information needed.
                  It really help