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Misc solar questions

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  • Misc solar questions

    1- 12v vs 24v. I've read for solar systems exceeding ~600w, one should consider going to 24v - if no DC load exceeds ~30amps. The reason for this apparently is because most step down converters can't handle more than 40 amps or so. But since many towable RV's have hydraulic leveling systems that draw more than 40amps, it seems nobody could take advantage of a 24v system. What am I missing?

    2- 12v vs 24v solar panels. It sounds like if I go with a 12v system I should use 12v panels. But, I've only found ONE manufacturer (Victron) that shows the panel voltage (12v vs 24v). Every other manufacturer I've looked into lists two dozen specs for their panels but not one of them identifies them as 12v or 24v. Clearly I'm missing something. This information must be buried in all the other specs that are listed. Does anybody know how to identify whether a panel is 12v or 24v?

    3- Inverter vs inverter/charger. The vast majority of people that build solar systems seem to get a combination inverter/charger. Do these people disconnect their factory converter/chargers? Are they getting combo units because they haven't yet replaced their OEM charger for a model that will charge LiFePO4? Can you leave the OEM charger/converter in place and use a combo inverter/charger at the same time?
    Brian & Kellie
    2020 Grand Design Solitude 310GK-R, FBP, MORryde IS w/ disc brakes, 1,460w solar
    2020 Ford F-350 Platinum SRW PSD Tremor, 60g TF fuel tank, Hensley BD3-F air bag hitch

    Previous setups:
    2019 Grand Design Solitude 373FB-R, 2019 Ford F-350 Platinum DRW Powerstroke, Hensley BD5 air bag hitch
    2016 Grand Design Reflection 318RST, 2016 GMC 3500 Denali SRW Duramax, Hensley BD3 air bag hitch

  • #2
    Originally posted by bertschb View Post
    12v vs 24v. I've read for solar systems exceeding ~600w, one should consider going to 24v - if no DC load exceeds ~30amps. The reason for this apparently is because most step down converters can't handle more than 40 amps or so. But since many towable RV's have hydraulic leveling systems that draw more than 40amps, it seems nobody could take advantage of a 24v system. What am I missing?
    It becomes a lot easier to understand once it it clear that the only purpose for the solar panels (and solar controller) is to charge the battery bank. Period. Nothing else. Being able to power systems in the trailer is dependent on the battery bank state of charge (SoC), the battery bank's capacity to deliver power, wiring, and (if running an inverter) the capability of the inverter.

    Originally posted by bertschb View Post
    12v vs 24v solar panels. It sounds like if I go with a 12v system I should use 12v panels. But, I've only found ONE manufacturer (Victron) that shows the panel voltage (12v vs 24v). Every other manufacturer I've looked into lists two dozen specs for their panels but not one of them identifies them as 12v or 24v. Clearly I'm missing something. This information must be buried in all the other specs that are listed. Does anybody know how to identify whether a panel is 12v or 24v?
    There's a difference between the output of the solar panels (going to the input of the solar controller) and the output from the solar controller. To my knowledge there's no such thing as a "12v panel". Panel voltage will vary greatly depending on the solar conditions, shading, etc.

    For example, the 300W Jaboni that GD uses can have a maximum output of 32.26v at 9.3 amps. (Quick math: 32.26*9.3=300 watts) Specs are from https://www.jabonipowerproducts.com/...00_9.16.19.pdf

    A solar controller will convert what it's getting from the solar panels via it's input to either 12v or 24v on the output,depending on how the controller is configured. (Note that "12v" means the proper charge voltage for the battery--for the Battle Born this is typically ~14 v but for simplicity let's stay with 12v.) Given it's a 12v system the output of the controller is connected to, 300W/12v = 25 amps going to the battery bank. Bottom line: I've had no issues with the 1200W system in my 315RLTS with the Victron MPPT controller staying with a 12v system. (Why? Because the output wiring from the MPPT to the battery bank is very short and is a relatively large 2 ga.)

    Originally posted by bertschb View Post
    The vast majority of people that build solar systems seem to get a combination inverter/charger. Do these people disconnect their factory converter/chargers?
    Yes

    Originally posted by bertschb View Post
    Are they getting combo units because they haven't yet replaced their OEM charger for a model that will charge LiFePO4?
    Yes, and so they can charge the LifePO4 at the .5C rates usually recommended (typically 50A per battery) which usually requires short wire runs of a very large gauge. I have 4/0 between the Victron and the battery bank.

    Originally posted by bertschb View Post
    Can you leave the OEM charger/converter in place and use a combo inverter/charger at the same time?
    Disconnected is recommended. I removed mine completely. I saw no need to have a backup since I never had one for the WFCO which is much more likely to fail (IMO) than the Victron.
    Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

    Howard, 2017 Ford F-350 DRW, '19 315RLTSPlus

    Comment


    • #3
      Thanks for the feedback Howard

      I understand the only purpose of solar is to charge batteries. But, I still don't understand how people with towable RV's with hydraulic pumps can take advantage of a 24v system (battery bank configured to 24v, 24v controller and inverter, etc). I guess it doesn't really matter since almost everybody sets up 12v systems for RV's. The hardware for 24v systems is much cheaper so it's attractive.

      Here are screen shots from the Victron site showing their solar panel offerings with both 12v and 24v panels:

      Click image for larger version

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      Brian & Kellie
      2020 Grand Design Solitude 310GK-R, FBP, MORryde IS w/ disc brakes, 1,460w solar
      2020 Ford F-350 Platinum SRW PSD Tremor, 60g TF fuel tank, Hensley BD3-F air bag hitch

      Previous setups:
      2019 Grand Design Solitude 373FB-R, 2019 Ford F-350 Platinum DRW Powerstroke, Hensley BD5 air bag hitch
      2016 Grand Design Reflection 318RST, 2016 GMC 3500 Denali SRW Duramax, Hensley BD3 air bag hitch

      Comment


      • #4
        OK, follow up question-
        Since I already replaced my OEM charger/converter with a Progressive Dynamics PD9160ALV, is there any advantage to getting a combo Victron inverter/charger?
        Brian & Kellie
        2020 Grand Design Solitude 310GK-R, FBP, MORryde IS w/ disc brakes, 1,460w solar
        2020 Ford F-350 Platinum SRW PSD Tremor, 60g TF fuel tank, Hensley BD3-F air bag hitch

        Previous setups:
        2019 Grand Design Solitude 373FB-R, 2019 Ford F-350 Platinum DRW Powerstroke, Hensley BD5 air bag hitch
        2016 Grand Design Reflection 318RST, 2016 GMC 3500 Denali SRW Duramax, Hensley BD3 air bag hitch

        Comment


        • #5
          Originally posted by bertschb View Post
          I understand the only purpose of solar is to charge batteries. But, I still don't understand how people with towable RV's with hydraulic pumps can take advantage of a 24v system.
          These folks have a down-converter that changes the 24V to 12V. The advantage in systems that carry a lot of amperage or have long wire runs is the 24V (obviously) only has to transmit 1/2 the amps for the same wattage. Over long wire runs or very high amperage loads it might be worth going to a 24V system, but for most of us with relatively small systems (and short wire runs with sufficient gauge wires) a 12V works out just fine. It's all about losses in a system. An engineering analysis of the loss converting from 24V to 12V would have to be compared to the losses accumulated in a pure 12V system. Again, for most of us there's little gain (if any) from adding in the complication of a 24V system. (Remember I'm just a shadetree tech at best...so what's written here is just an opinion.)

          Originally posted by bertschb View Post
          Here are screen shots from the Victron site showing their solar panel offerings with both 12v and 24v panels
          This took me a few minutes to figure out, because it didn't make sense (at first).

          Look at the specs at https://www.victronenergy.com/upload...-Panels-EN.pdf. Note in the first column there's a row labeled Number of cells in series. For a "12V" panel, there are 36 cells. The math says each cell generates .33v, so 36 cells in series generates 12v. Now look at the 305W panel--it's a 20V panel. That's because there are 60 cells in series. 60 * .33v = 20v. Same logic applies to the "24v" panels. 72 cells in series * .33v = 24v

          The next obvious question--why have the different number of cells in series? It's the balance of "series" vs "parallel" in a solar setup and where/how to insert bypass diodes on the panel. I wrote a thread on it that might help you understand. Bypass Diodes in Solar Panels

          Bottom line: the panel designation on Victron's site does not equate to a battery voltage configuration.

          Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

          Howard, 2017 Ford F-350 DRW, '19 315RLTSPlus

          Comment


          • #6
            Originally posted by bertschb View Post
            OK, follow up question-
            Since I already replaced my OEM charger/converter with a Progressive Dynamics PD9160ALV, is there any advantage to getting a combo Victron inverter/charger?
            A Victron 12/3000 Multiplus can charge at twice the rate (120 amps) of the PD9160 (60 amps). I write that based on the maximum output on Progressive's website at https://www.progressivedyn.com/pd9100-converter-2/ and Victron's at https://www.victronenergy.com/upload...120V-US-EN.pdf

            If I remember correctly you'll have four 100aH Battle Born batteries. The ideal charge rate for a Battle Born is .5C (50A) or less. What that means is with four 100aH batteries in parallel, the Victron can go full throttle and provide 30A to each battery simultaneously. The Progressive would deliver no more than 15A to each battery simultaneously. Theoretically that means the Victron will recharge the batteries in 1/2 the time of the Progressive.

            Is that time difference worth it? That's up to you.

            I can with confidence write that if you can invest in a Victron setup, once you have it up and running you'll like the ability to monitor the devices via the VictronConnect app. It just works. (Neil will back me up on that statement! ncitro ) Spend a few extra dollars and get a GX device and it's really awesome (like the Color Control GX that I have). It's expensive--but if the budget will allow it's fantastic tech.

            Howard
            Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

            Howard, 2017 Ford F-350 DRW, '19 315RLTSPlus

            Comment


            • #7
              I definitely agree, the central monitoring of all the devices makes the system much easier to manage. There’s a few options they offer, the color control, the Cerbo, or what I did was load their software onto a raspberry Pi with touchscreen. Victron has a project where they provide a pi distribution with the software loaded and ready to go. If you’re comfortable with a bit of Linux it can save you some money.
              Neil Citro
              2018 Reflection 28bh
              2019 F350 6.7L Long Bed Crew Cab

              Comment


              • #8
                Originally posted by howson View Post
                A Victron 12/3000 Multiplus can charge at twice the rate (120 amps) of the PD9160 (60 amps).
                As I was riding my bike just now I started thinking the Victron charger was probably rated at higher amperage. That's a huge advantage. I don't yet understand the differences between all the various Victron products so I need to spend a few hours on their website and see I can narrow down my options.

                Thanks again for feedback and the clarification on the 12v/24v panels.
                Brian & Kellie
                2020 Grand Design Solitude 310GK-R, FBP, MORryde IS w/ disc brakes, 1,460w solar
                2020 Ford F-350 Platinum SRW PSD Tremor, 60g TF fuel tank, Hensley BD3-F air bag hitch

                Previous setups:
                2019 Grand Design Solitude 373FB-R, 2019 Ford F-350 Platinum DRW Powerstroke, Hensley BD5 air bag hitch
                2016 Grand Design Reflection 318RST, 2016 GMC 3500 Denali SRW Duramax, Hensley BD3 air bag hitch

                Comment


                • #9
                  Originally posted by bertschb View Post

                  As I was riding my bike just now I started thinking the Victron charger was probably rated at higher amperage. That's a huge advantage. I don't yet understand the differences between all the various Victron products so I need to spend a few hours on their website and see I can narrow down my options.

                  Thanks again for feedback and the clarification on the 12v/24v panels.

                  Yeah as your battery bank grows you will find your charging needs increase. Especially if you are planning for a generator (for cloudy days etc) then the bigger the charger, the less time the generator needs to run. Saves fuel and noise.
                  Neil Citro
                  2018 Reflection 28bh
                  2019 F350 6.7L Long Bed Crew Cab

                  Comment


                  • #10
                    Originally posted by howson View Post


                    Disconnected is recommended. I removed mine completely. I saw no need to have a backup since I never had one for the WFCO which is much more likely to fail (IMO) than the Victron.
                    I left my converter in installed but unplugged as a backup to my Magma inverter/charger. The inverter/chargers can and do fail if only infrequently but with the converter you are still fully functional on failure if plugged in. I have also had to use the converter to wake up my BB batteries when the BMS has shut them down. They show essentially 0 volts at that time which is too low for the “intelligent” charger to charge them. The basic WFCO charger hits them with 13+ volts and they are good to go again. Otherwise, the only other place to get the voltage would be to hook up the truck.
                    2018 Reflection 303rls
                    2017 Ford F350 SRW

                    Comment


                    • #11
                      Originally posted by wygieman View Post

                      I left my converter in installed but unplugged as a backup to my Magma inverter/charger. The inverter/chargers can and do fail if only infrequently but with the converter you are still fully functional on failure if plugged in. I have also had to use the converter to wake up my BB batteries when the BMS has shut them down. They show essentially 0 volts at that time which is too low for the “intelligent” charger to charge them. The basic WFCO charger hits them with 13+ volts and they are good to go again. Otherwise, the only other place to get the voltage would be to hook up the truck.
                      When I ran my Battle Borns (BBs) unintentionally flat it was the CCGX (Color Control display) device that caused the problem with the Multiplus refusing to charge the BBs. With the CCGX connected to the Multiplus, the Multiplus would not start charging until the CCGX powered on. The CCGX would not power on because the BBs were flat. See the problem?

                      All I had to do was disconnect the CCGX and the Multiplus started recharging the BBs without an issue.

                      How other "smart" inverter/chargers would react in this same scenario I don't know.

                      Regarding leaving the WFCO--there is merit to leaving it installed. I didn't have the space in my 315RLTS' hutch due to the EMS and Smart ATS installation. (It's not a big space!)
                      Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

                      Howard, 2017 Ford F-350 DRW, '19 315RLTSPlus

                      Comment

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