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Need help reviewing design for my RV conversion solar

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  • #16
    Man, I am hard headed.
    Really don't want to connect to my starting batteries. I understand the alternator is great at generating power if I am running it, but I expect to park the bus for a few days once I get to my where I want to stay.

    So that being said, I am thinking 24v battery bank again, and have tried to update my drawing to reflect changes.
    Hope to be purchasing some parts this week.
    Any feedback greatly appreciated.

    Also a couple of other questions
    Where do I need to put switches?
    I had purchased a meter with a shunt, where should it go?
    Is there a special inline type fuse i should be using when not on the distribution block.

    Thanks!


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    • #17
      Sunking Didn't we say a long while back that the chassis grounds like the 3 green in your second pic were bad?

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      • #18
        Originally posted by joerossjr View Post
        Sunking Didn't we say a long while back that the chassis grounds like the 3 green in your second pic were bad?
        Bad how? Not sure I am following you. Although not required for normal operation, they are required to enable fuses and breakers to operate correctly. Minimum wire size vary according to breaker sizes, but needed regardless on a Grounded System.

        Perhaps we are not on the same page?
        MSEE, PE

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        • #19
          Sunking Ground loops and bypassing shunts (if installed).

          https://www.solarpaneltalk.com/forum...chassis-ground

          Second page actually addresses it more.
          Last edited by joerossjr; 10-09-2018, 01:54 PM.

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          • #20
            Originally posted by joerossjr View Post
            Sunking Ground loops and bypassing shunts (if installed).
            So why would you put a Shunt on the Grounded Return Conductor and make a a problem for yourself? Eliminate the problem by not creating it in the first place, and put it on the Battery Supply Lead where it is suppose to be?
            MSEE, PE

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            • #21
              Sunking Because as you have pointed out to me (and I learned by frying one) these simple DROK meters do not go on the positive side of the system. "It's just the way they are built." I have a floating system that is connected to the other battery via the negative post. I do not use the chassis as a ground.

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              • #22
                Originally posted by joerossjr View Post
                Sunking " I have a floating system that is connected to the other battery via the negative post. I do not use the chassis as a ground.
                Perhaps not.

                If you mean the "other battery via the negative post" is the vehicle SLI battery, your system is grounded solidly to the vehicle frame. If that is a correct assessment, would need to remove any fuses or breakers going to the House Batteries Negative Term Post.

                In a Floating System, if that is what you think you have, would require Fuses/Breakers on all Negative polarity lines doubling fuse and breaker requirement count. However it does not exempt you from bonding requirements of the chassis of the controller, inverter, and panels to the vehicle chassis.

                As soon as you reference the House Battery to the SLI Battery, you automatically are committed to a Grounded System because the SLI Battery Negative Term Post is solidly bonded to the vehicle frame/chassis, and must remain that way.. So your House Battery is default Bonded. Now you do not have to spend all that extra money on all those fuses and breakers.All you have done is moved the bonding point further away from the house battery to the vehicle engine compartment.
                Last edited by Sunking; 10-09-2018, 04:25 PM.
                MSEE, PE

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                • #23
                  Sunking @##$(&*&!!!!!!!!! I meant grounded. I don't know why I typed that. I do have fuses on all my POS sources. But back to the ground loop issues.... You've said "ground loop = bad" before, which made sense, but I am guessing that pic is applicable to houses and infrastructure that requires earth grounding, and therefore they use HE sensors instead of shunts like I am using. If that's the case, then I'll ignore the grounds from here on out since I know what you mean when I see them.

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                  • #24
                    Originally posted by joerossjr View Post
                    Sunking @##$(&*&!!!!!!!!! I meant grounded. I don't know why I typed that.
                    No problem ,happens to all of us. He!! I use to drink and smoke. I was young and dumb once upon a time. Now I blame my acts of stupidity on age. At some point we quit thinking with our d....k's

                    OK Earth Ground and Chassis ground are different, but exactly the same thing. It depends on what regulatory standard you are talking about, and how it is used. All Ground means is a conductive body like earth or something in place of earth. Example; we can use a ham sandwich to reference your system too. Especially the way I make a ham sandwich with lots of mayo and tomato making it real conductive. Or Ground can be something like a frame of a car, boat, train, and aircraft. So when you hear the term ground, does not mean dirt. it is a REFERENCE POINT we call ZERO VOLTAGE

                    Now how ground is used depends on who's rule book you follow. In NEC application like those used in homes and buildings forbid ground, either by dirt or a copper conductor, to ever be used for normal load currents. Only thing ground is there for inside your home to provide a Planned Path back to the Service Transformer Grounded Circuit Conductor aka Neutral. And provides Zero Voltage Reference with respect to earth so when you touch something electrical will be at 0 voltage with respect to what you are standing on.

                    Switch over to autos and RV and you have different set of rules. Not only can you run current through ground (frame and chassis), it is used as a conductor so you only require running one wire to your gizmo. All your power windows, seats, door locks, and lighting only use one wire from the battery, and the frame for the return path. If you pull electrical drawings from say you modern automobile, you will find in the wiring harnesses will carry heavy ground wire, and along the length of the harness the ground wire will be broken out at strategic locations and bonds to the frame of the car at many points. Making your car one large Ground Plane. Example as the two Harnesses go down each side of the car going back you will see a bond to the Seat Hard Points and the wires for seat heater, power seats break out.

                    So in a NEC application, there is one one Ground Bond allowed, and no more downstream. That way you have no loops allowing current to flow on ground conductors as the only job is to provide a low resistance path back to the source to facilitate operation of over current protection devices, and provide a zero voltage touch potential. If you allowed current o flow on the ground would cause a voltage drop and potential shock hazard.

                    Auto industry uses ground as a conductor. Why, because it is not 120 volts, shock potential is null, and it saves a lot of weight and money not having to use two wires.
                    Last edited by Sunking; 10-09-2018, 06:10 PM.
                    MSEE, PE

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                    • #25
                      Sunking Uhhh... d**ks, ham sandwiches???? You sure you quit drinking???

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                      • #26
                        Originally posted by joerossjr View Post
                        Uhhh... d**ks, ham sandwiches???? You sure you quit drinking???
                        Nope dead serious. You can reference your electrical system to a ham sandwich. Your dang car is referenced to the chassis and insulated from ground. It is just a 0 volt reference point. A ham sandwich will work just as well.
                        MSEE, PE

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                        • #27
                          Originally posted by Sunking View Post

                          Use them for now, fix it later when they need to be replaced. Listen up here is what I would tell any RV'er. RV design process is not the same as a fixed stationary. The very first step is determine your daily Kwh. So lets say 2 Kwh per day. In an RV size your battery for 3 day reserve or 6 Kwh. Determine battery voltage which is typically 12 volts in n RV. To find the AH = Watt Hours / Battery Voltage. So a 6000 watts / 12 volts = 500 AH. That knocks off the battery drill. The rest is super easy. Forget all the formulas to calculate panel wattage, it is not going to work. Instead we design the system to provide a perfect C/10 charge rate, and a 500 AH / 10 H = 50 Amps. That takes care of the Controller selection. For the panels you just find what wattage required to deliver 50 amps charge current. Panel Wattage = Amps x [Battery Voltage. 50 amps x 12 volts = 600 watts. Your done, have a safe trip.

                          If your batteries get low, run genny or drive a while if you have an Isolator to charge the batteries from the alternator.
                          My plan is to full time RV for several years and get the maximum amount of power available from a 12v LiFePo4 battery system.

                          1. Daily power requirement is 4kWh/day.
                          2. 4kWh x 3 day reserve = 12kWh / 12 volts = 1000 AH Battery Bank
                          3. 1000 AH / 10 H = 100 Amp Controller
                          4. 100 Amp x 12 volts = 1200 watt solar panel

                          1. Daily power requirement is 3kWh/day
                          2. 3kWh x 3 day reserve = 9kWh / 12 volts = 750 AH Battery Bank
                          3. 750 AH / 10 H = 75 Amp Controller
                          4. 75 Amp x 12 volts = 900 watt solar panel

                          1. Daily power requirement is 2kWh/day
                          2. 2kWh x 3 day reserve = 6kWh / 12 volts = 500 AH Battery Bank
                          3. 500 AH / 10 H = 50 Amp Controller
                          4. 50 Amp x 12 volts = 600 watt solar panel

                          Note to self. Will continue to price out options and see where this goes.

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