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which controler for my needs

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  • which controler for my needs

    Hi everyone ,
    I dint want to enter specific numbers ,because this subject could be used with different data .....
    I have 3 different solar systems on my RV , and I want to simplify this ...
    My project is to get two 300 watts 24 V panels .....I was told to install them in series to get 48 V system ......Is this a good idea ? If so , what amperage rating controler should I get ?
    If I go ith the formula the higher voltage the lower amperage ,right ? or am I wrong ?
    what about in parallel to keep 24V ? better or not ? would the 48V system be more performing then the 24v ?

    thanks for the advices , I`m quite new at this ! But I like to learn lollll

    Daniel ,

  • #2
    What voltage are the appliances in your RV ? 12V ? 48V ? 120VAC ?
    What voltage is your charging system ? Big rigs have 24Vdc systems.

    It's handy for the RV house battery to be the same voltage as the vehicle charging circuit. If your power needs are beyond what 12Vdc can supply, then going up in battery voltage is required.

    I run my house and ranch off a 5KW 48V system. A mobile RV is not likely to require the same amount of power.. With the advent of the cheap, small, quiet 1,000 inverter generators, the game has changed for power storage. ( a gallon of gas contains a lot of energy )
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A



    • #3
      sorry ,should have tought of this
      all is on 12V DC .....
      I also have a 1500W inverter for my morning coffee and for the TV ( 24 " 45w )

      do you think the victron 100/30 would be a good MPPT choice
      Last edited by BigDan; 06-11-2019, 07:34 AM.


      • #4
        some say I need 20 amp controler 60 watts divided by 48= 12,5 amps .........other say 60 amps because ill get up to 72 volts peak .... ....Id like to get the right answer


        • #5

          your 600 watts of panels will generate a bit over 40 amps if all is perfect but that is rarely reached. A 40 amp controller would work for you on this project. With an R.V. shading is an issue so I would wire the panels in parallel, and with a MPP voltage of about 36 volts will work well with a 40 amp MPPT controller on a 12 volt system.


          • #6
            I'm no expert, but I have a 600W off grid system. I use the epever 4210AN 40 amp controller and I am very happy with it. As mentioned its very unlikely you will ever get the peek output of the panels. You can wire the panels in series to up the voltage and let the controller step it down to your batteries voltage (this is what I have done). It works rather well.
            The epever should be able to take the voltage of your panels, as it goes up to 100volts.

            I understand the Victron are excellent controllers, and have lots of settings to tweak via a computer. I have never had one so perhaps others might tell of their experience.


            • #7
              Umpa, and BigDan,

              A MPPT controller has a best range of voltage conversion, putting two panels in series results in a voltage conversion ratio of 70/14 or 5:1 down conversion ratio, however putting the panels in parallel results in a down conversion ratio if 35/14 or 2.5:1, The higher the conversion ratio the less efficient a buck converter operates and will produce less power output and will create more heat in the controller. Heat is the enemy of power electronics. So that is why I recommend the parallel wiring for this 35 volt at MPP into a 12 volt battery bank.

              So three advantages to parallel connection in this case, less shading issues, more power , and less heat!

              Comparing the Victron to the EP Solar tracer is like comparing a Mercedes to a Yugo........The Victron is by far the better controller, it's fully adjustable, made by a reputable company that does have end user support!

              Ive had both, no comparison!



              • #8
                I have a similar question on a very similar setup. I currently have a 275 watt panel and have just bought another one rated at 310 watt.
                I wanted to buy another 275 but they just keep selling more watts for the same price. Couldn't even find a comparable panel at the same size and it's been only less than a year.

                Anyways, I have a VictronConnect 30 amp MPPT and a 12 v battery system.

                I do have some shading through the day.
                I have been to two different stores in my area and have had completely different advice on how to wire the panels and what CC I will now need.

                If if I use my current CC with a 30 breaker on the array input line before my CC, will that be OK. I really don't want to buy another CC for the 50 amp rating that the 1 store said I should do. Ughhh ! Help please. Series ? Parallel ? Breakers ? I have a 150 amp terminal battery fuse and also a 200 amp one.

                2000 watt pure sine inverter for my fridge and the rest is 12 v low amp led lights.


                • #9

                  I do not know just what two panels that you have but if they are both 60 cell grid tie types, then wire them in parallel. The 30 volts at MPP is enough for the Victron controller to work just fine. Generally panels within a few volts of each other will work in parallel but if you have one 60 cell panel and one 72 cell panel you will not get the maximum power available. My rough rule of thumb is a 60 cell polycrystalline panel will work well with any other 60 cell polycrystalline panel in parallel. They will be very close in voltage, also mismatched 72 cell panels will be close to the same voltage and will work in parallel. Two mismatched panels in series will result in the smaller wattage panel "throttling" down the current of the larger wattage panel to that of the smaller wattage panel.

                  The total STC power generated by the two panels will be at 125% of the Victron controllers rated specifications (41 amps roughly) but seeing that 71% of "STC" (the average power actually output) is 29 amps or so the controller "should" be able to handle it. That said I have not run any Victron Controller at that power level. Generally it is not a good idea to run electronic eat maximum power for extended run times. In solar use most times the controller would not be operating at maximum power for extended periods.
                  Last edited by Tecnodave; 06-15-2019, 06:34 PM.


                  • #10
                    So basically I am right on the edge as it seems.
                    Maybe I will just buy another 310 watt panel
                    to be properly paired and upgrade my CC to the 50 amp VictronConnect.
                    I can sell my other panel to offset the upgrade cost.


                    • #11

                      In the long term that would be a good choice, I like to run my controllers at 60% power, they run cooler and last longer, I have the 96 amp MidNite Classic 150's 5 years now and nary a hitch, they just work!


                      • #12
                        Ok ,then I should go to connect the 4 wires in the flimsy controler connectors ? With some Y junctions ?


                        • #13

                          The easy way would be get a pair of "Y" connectors and an solar extension cable twice as long as the distance from panels to controller and cut it in half. Use the connectors to connect to the "Y" connectors and the cut ends to the controller, Do use a circuit breaker between the p.v. positive wire and the positive terminal on the controller and another breaker between the Victron controller and the battery. Sizing..p.v. 30 amp, battery feed to controller 60 amps

                          In use of an MPPT controller power up the controller first, let it initialize, then turn on p.v. breaker, when nessecary to power down system turn off solar first, wait a minute, turn off battery breaker. Reason....some MPPT controllers will be damaged by having p.v. input with no battery connection.


                          • #14
                            Originally posted by Tecnodave View Post
                            Reason....some MPPT controllers will be damaged by having p.v. input with no battery connection.

                            Plus many controllers will look at incoming battery voltage to automatically determine system voltage. That being said it is wise to start with a fully charged battery bank. I've heard of people trying to start with dead batteries and having the controller determine system voltage incorrectly.
                            Last edited by littleharbor; 06-16-2019, 07:58 AM.
                            2.2kw Suntech mono, Classic 200, NEW Trace SW4024