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  • Advice on RV Set up & Wiring?

    I'll start out by saying I'm a bit of a noob to solar, I have some experience with electrical, I'm fairly handy, and I'm in the process of learning how to design & set up the system I'm looking for and could use some advice on how to make what I want to do work properly.


    I have an enclosed trailer that I use for trips to the CA desert, the trips are usually 3 days but can be up to 5 days on occasion and I'm in the process of gathering & installing the equipment I'll need for my solar system and I'm looking for advice on design, equipment, & how to wire it 8/10 times I have full sun.


    My goal is to run my mini fridge (converted mini vertical freezer) off of the batteries through a pure sign wave inverter without draining the batteries or running it off of my generator while I'm on my trips. (I went with a mini fridge & solar over propane due to the cost of a used propane fridge alone being $500+, the propane fridge size being too large to fit under my work bench, having to mount and plumb propane lines which my trailer does not currently have, and I like having 2 charged 6Vs to run my 12V LED lights in the trailer, so before you say just get a propane fridge I've weighed my options and this is how I've decided to go as it fits my needs and I can build the whole solar system for the cost of a used propane fridge alone).

    [U]I currently have:[/U]
    -2 -6Vs mounted on the trailer tongue wired in series (there is not room for 4 -6V with the current battery tray configuration and it is not worth altering it to me, I'm in the 12V box)
    -Mini Fridge rated at 1.1A or about 120W, which is a converted vertical mini freezer that probably runs 3 out of every 15-20 minutes for cycle run time.
    -1500W Go Power Pure Sine wave inverter, Note, I'm ONLY using this to run the fridge and been told by Go Power that it only pulls the DC load required to power what ever is pulled on the AC side which is 120W, so not in fire danger.
    -I've ran 1/0 on the battery set up and 10 foot positive power lead into the trailer where I'm mounting the Inverter & solar charger
    Note: I've also made a test run with these batteries, this inverter, & this fridge and it went 72 hours and drained the batteries to 11.8V and this is why I need solar to keep the batteries charged, the fridge working and the lights on so charging and running off batteries only is not an option.

    [U]I Currently Need to get:[/U]
    -Solar panel or panels
    -MPPT charge controller


    [U][B]Design Questions:[/B][/U]
    I plan on getting one 315 or 335W panel (or I can get two 200-225W panels) BUT I prefer a single panel for mounting space reasons.

    [B]Q-1)[/B] Is there any difference between running one panel or two panels? I understand wattage differences but is there an advantage or dis-advantage to running one VS two panels?

    [B]Q-2)[/B] If I go with a single 315W 60 or 72 cell panel I can do a 30A MPPT controller, if the price is negligible does it matter with my current system design if I go with a larger controller say a 60A or an 80A so I have extra controller capability if I want more panels in the future can the controller be turned down or it can not be turned down and will this fry my current batteries becuase too many Amps being fed in to the system?

    [B]Q-3) [/B]With my current set up and a 30A or 40A controller how fast will the batteries charge (assuming average desert sun) and what happens to the incoming electricity once the batteries are full?

    [B]Q-4)[/B] If I remove the 2 -6V batteries from the system and the inverter is turned off, what happens to the incoming electricity from the MPPT controller, the DC line is still live or can I turn the controller off and what the panels are producing just gets eaten by the charge controller?


    [U][B]Wiring Questions:[/B][/U]
    I have made a diagram of how I think I'd like to run the wiring but I do have a few questions to make sure I'm not creating any issues or dangers (see attached diagram).
    [B]Q-1) [/B]Instead of making runs to the battery terminals for the inverter & solar charge controller can I just install a distribution block locally where the equipment is mounted and tie them all together there instead of at the battery terminals on the positive side?

    [B]Q-2)[/B] On the negative side, I have welded a bolt to the frame locally where the inverter & charge controller will be mounted on the inside of the trailer can I run both negative leads to this bolt and mount them together instead of making runs back to the negative battery terminals?

    [B]Q-3)[/B] The inverter has a chassis ground that is grounded to the GCFI plug on it, if I connect the chassis ground to the same terminal as the DC negative lead I believe it will create a ground loop and trip the GCFI, is this correct? If so I need to just leave the chassis ground NOT connected/grounded, correct?

    Attached Files
    Last edited by Carv; 05-11-2017, 01:44 PM.

  • #2
    Welcome,
    Well you are asking good questions. here are some possible answers,

    The question you DIDN'T ask, is [B]how much PV will I need to power my gear to keep my batteries healthy ?[/B]
    Get a "Kill-a-watt" meter and measure your fridge for a week of use at home, and figure your daily KWh usage.
    I expect you will require 1KWh daily just for the fridge, and more for lighting, fan, laptop, phone.....
    [B]Can 400W of PV harvest 200% of your daily load[/B] ? Only expect 4 solar hours winter, 5 or 6 in summer, even in the desert

    Design Questions:
    1) watts are watts, as long as you stay under the kill voltage of your controller.
    Volts "transport" easier, thin wire, Amps need thick expensive wire

    2) Better controllers do allow a programmable Max Amps to lessen BBQ'ing your batteries.

    3) How much concurrent load will the system see? if you divert charging amps from the
    batteries to the inverter to power the fridge, the batteries take longer to charge.
    With new batteries, expect 20A out, to be replenished with 24A back in. (80% efficient) Older batteries are less efficient.
    With a MPPT controller, expect 95% of the watts IN to come out for loads & charging

    4) MPPT controllers Must remain powered by a battery whenever the solar input is connected. The stable battery voltage is where the Brains (CPU) is powered from. Always connect to battery first, wait for it to boot, then connect solar. Reverse sequence for power down, or you get to buy a new controller.


    Wiring Questions:

    1) The 200A breaker at the battery protects the 200A wire (4/O) you have running to the + Bus.
    Each wire coming off the + Bus, needs to have it's own protection, 10ga wire needs 30A
    12ga wire needs 20A, use the NEC gauge/amps chart to select the protection for each wire.
    (google "NEC AWG wire ampacity", the first 3 results are pretty good)
    Large wire sizes 2/O, 4/O use the capital o, not zero O 0
    Any wire larger than #8ga requires a 6-12 ton hydraulic crimp tool to make a secure, safe connection,
    or purchase pre-terminated wires. The cheap hammer type crimp tool does not always make a secure
    connection.
    It's always safe to use a larger wire, on a small fuse, than a small wire on a large fuse.
    (think burning insulation and white hot wire)

    2) You can use a common - terminal, don't expect to carry any amps through the trailer frame, some joints are painted and bolted, some have rubber damping material.....

    3) inverter grounding. Follow the rules that come with the inverter. Consider the chassis bolt to be the ground rod, since mobile trailers aren't required to be wired to a ground rod. (picture a campground where folks for a season, leave ground rods behind)


    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

    Comment


    • #3
      Thanks for the answers Mike, some make it clearer some make it muddier

      That is a good question on how many panel watts I'll need. Since higher panel watts equal higher controller volts I assume I'll be limited at a certain point by finances and what I can pick up used. I'm thinking I'll probably max out around 60A MPPT based on price which would limit me to 720W or less. Since I'm approaching this from the reverse I think I'd be better off figuring out how many watts the various panel(s) will make based on their rating and figure out what is a sufficient amount to run my set up or at least get close without over taxing the battery charge amps and frying them or decreasing their life span prematurely.

      Is there an equation for actual panel wattage production based on rated watts? I can also make my panel(s) tilt if need be and I can position my trailer for max sun when I initially park it plus I'm in the southern CA desert not far from Mexico & Arizona so there is lots of intense sun exposure.


      I do have some further questions to help clarify things based on your answers:

      Design Questions:
      1) watts are watts, as long as you stay under the kill voltage of your controller. Volts "transport" easier, thin wire, Amps need thick expensive wire
      [COLOR=#0000cd]Q) Since I'm in the 12V box I assume I'll need thicker wire due to higher amps but that thicker wire is from the controller to the batteries or positive distribution block NOT from the panels, to the solar charge controller correct?[/COLOR]

      2) Better controllers do allow a programmable Max Amps to lessen BBQ'ing your batteries.
      [COLOR=#0000cd]Q) Does a Morningstar MPPT TS have this feature? also what are some other recommended MPPT controllers in the 30A to 60A range?[/COLOR]

      3) How much concurrent load will the system see? if you divert charging amps from the batteries to the inverter to power the fridge, the batteries take longer to charge.
      [COLOR=#0000cd]Q-1) The fridge is rated at 1.1A AC not sure what the inverter will pull DC to make 1.1A AC? Either way it's coming form the charge controller and since the batteries have inefficiencies in them hence your 80% conversion for new batteries, wouldn't it be better to run the inverter directly off the charge controller while the current is there and then off the batteries when it's not? But since there is no way to switch between the two & there would be draw for both the batteries & the inverter I guess the question you're getting at is; if there is enough DC AMPs to charge the batteries AND run the fridge at the same time, with a 1.1A AC rating can I assume it'd take very little DC Amps to run the fridge??? Is there a conversion equation for this?[/COLOR]
      [COLOR=#0000cd]Q-2) W[/COLOR][COLOR=#0000CD]hat happens to the incoming DC from the charge controller once the batteries are full? [/COLOR]

      4) MPPT controllers Must remain powered by a battery whenever the solar input is connected.
      [COLOR=#0000cd]Q) Do most MPPT controllers have a "Disconnect" for the Solar input line that kills any current coming from the panels? If so, there'd be current in the solar input line but it's just disconnected between the panel(s) and the charge controller and I could remove the batteries with no worry about any discharge or live line issues while the trailer is not in use? [/COLOR]


      Wiring Questions:

      1) The 200A breaker at the battery protects the 200A wire (1/O) you have running to the + Bus. Each wire coming off the + Bus, needs to have it's own protection, 10ga wire needs 30A
      [COLOR=#0000CD]Q-1) Can I just skip the 200A at the battery and fuse each component (inverter & controller) instead?
      Q-2) what type of fuse is recommended a shunt an actual fuse, a reset-able breaker??[/COLOR]

      2) You can use a common - terminal, don't expect to carry any amps through the trailer frame, some joints are painted and bolted, some have rubber damping material.....
      [COLOR=#0000CD]Q) My frame is all welded, BUT I'm not looking to carry any current through the frame I only want to avoid having to make multiple runs back to the negative battery terminal through the floor if it can be grounded to the frame locally. After all the batteries are grounded to the frame with the same set up (I welded a bolt to the frame at the battery tray).[/COLOR]

      3) inverter grounding. Follow the rules that come with the inverter. Consider the chassis bolt to be the ground rod, since mobile trailers aren't required to be wired to a ground rod.
      [COLOR=#0000CD]Q) I spoke to a C.S. rep at go power and they confirmed that if I run it chassis grounded to the negative terminal It creates a ground loop and trips the AC GFCI on the inverter. Not concerned with what is required as that changes depending on who you talk to and their knowledge and level of understanding of the system structure, I just want it to work correctly with no danger of causing issues. [/COLOR]


      [SIZE=14px][U][B]Thanks [/B][/U][/SIZE]
      Last edited by Carv; 05-12-2017, 05:41 PM.

      Comment


      • #4
        I have a feeling 720 watts of panels is overkill, I bet 600 watts (two 600 w panels) is just fine. Personally I'd go with a 40 amp charge controller since they get more expensive quickly as the capacity goes up.

        I recently built a system to the specs you're describing and posted the equipment list here, which might be useful:

        https://www.solarpaneltalk.com/forum...e-advice/page2

        Go down a few posts from that link.

        Last edited by Wrybread; 05-14-2017, 03:03 AM.

        Comment


        • #5
          Too late tonight to do another round of Q/A

          But what is "[COLOR=#0000CD]Q) I spoke to a C.S. rep at go power [/COLOR]" ?? CS computer science ? Corporate Supervisor ? Contract Sales ?

          I have a 24V inverter with internal GFI, and it's grounded to a Rod. Along with battery - & charge controller - & PV - , it all works Something is odd.

          You CANNOT (ok, should not) leave out any of the mentioned circuit protection devices. You have to pay, to safely play in the solar/battery game. Talk to someone who's had a electrical fire.
          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

          solar: http://tinyurl.com/LMR-Solar
          gen: http://tinyurl.com/LMR-Lister

          Comment


          • #6
            You really should put a fuse on your batteries. But that's ok, it's all easy and cheap. This is a great option:

            https://www.amazon.com/gp/product/B002INJXO6

            If you need to add an internal fuse box, I'm a big fan of these:

            https://www.amazon.com/gp/product/B001HC0QXG

            Or if you don't need that many circuits:

            https://www.amazon.com/gp/product/B001445O5W

            As far as your desire to power your fridge without impacting the batteries, I had the the same project in mind and wound up homebrewing something, but I didn't completely disconnect the batteries, I just turn on my fridge when the batteries are fully charged and there's enough power coming from the panels so it's in effect the same thing. But there's a few off-the-shelf products that have the ability to power an external load once the batteries are fully charged such as (I think) the Victon BlueSolar models:

            https://www.amazon.com/dp/B011KHV1RM

            Note that I haven't had any direct experience with those, and I'm not positive about that model, but I know some of their previous models had the ability. I'm pretty impressed with the programmability of their charge controllers in general, and the fact that they sell a bluetooth adaptor that lets you monitor the panels on a smartphone is a very good sign in my opinion. It looks like the Amazon seller at that link is answering questions that people post to the "ask a question" section of the Amazon listing so you might see if you can get a direct answer from him.

            Last edited by Wrybread; 05-13-2017, 06:42 AM.

            Comment


            • #7
              Originally posted by Mike90250 View Post
              Too late tonight to do another round of Q/A

              But what is "[COLOR=#0000CD]Q) I spoke to a C.S. rep at go power [/COLOR]" ?? CS computer science ? Corporate Supervisor ? Contract Sales ?

              I have a 24V inverter with internal GFI, and it's grounded to a Rod. Along with battery - & charge controller - & PV - , it all works.
              C.S. is customer service

              Thanks for the links wrybread

              my inverter calls for a 200A breaker on the DC positive lead so if I breaker each piece of equipment I assume I should breaker the inverter with the 200A it calls for? If I do it this way how many amps should I breaker the batteries with?

              i was thinking something like this that I can reset on site without having to replace a fuse if I'm in the middle of no where.

              https://www.amazon.com/Lumision-Wate...h+manual+reset

              Or this for 100A
              https://www.amazon.com/dp/B00139FQSS...=A6AY1HFZHO49U
              Last edited by Carv; 05-13-2017, 04:32 PM.

              Comment


              • #8
                The resetable circuit breakers (watch the label, get the one with the Test button on them, or termed SWITCHABLE) are a very good idea,
                Look at the Ampicity chart for the cable needed to safely carry 200A, that's what you have to use on a wire protected by a 200 A device, (i think 3/O or 4/O is required)
                Other wires, need to have a protection device, sized to protect the gauge wire you are using.

                The MorningStar TS MPPT 60 & 45 have a settable Max Amps limit - i've seen it in the menus.

                Fridge 1,1A @ 120VAC = 132watts @ 12V = 11Amps DC plus 20% for inverter losses, So you are looking at 13.2amps, at maybe a 40% duty cycle, 9.6 hours of runtime and total of 1,520 watt hours in a day

                Most MPPT controllers DO NOT have any disconnects built in, you need to supply that all externally. I used a 6 position breaker box to build my combiner, and also mounted my breakers for controller in it.

                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

                solar: http://tinyurl.com/LMR-Solar
                gen: http://tinyurl.com/LMR-Lister

                Comment


                • #9
                  Originally posted by Carv View Post

                  C.S. is customer service

                  Thanks for the links wrybread

                  my inverter calls for a 200A breaker on the DC positive lead so if I breaker each piece of equipment I assume I should breaker the inverter with the 200A it calls for? If I do it this way how many amps should I breaker the batteries with?

                  i was thinking something like this that I can reset on site without having to replace a fuse if I'm in the middle of no where.

                  https://www.amazon.com/Lumision-Wate...h+manual+reset

                  Or this for 100A
                  https://www.amazon.com/dp/B00139FQSS...=A6AY1HFZHO49U
                  I have one of those circuit breakers but I also have a 30amp in-line fuse to protect the wire. I only use the CB as a "switch" to disconnect my CC from my battery system.

                  Comment


                  • #10
                    These are handy and connect directly to the battery terminal:

                    https://www.amazon.com/gp/product/B002INJXO6

                    Comment


                    • #11
                      Originally posted by Wrybread View Post
                      These are handy and connect directly to the battery terminal:

                      https://www.amazon.com/gp/product/B002INJXO6
                      Those are great battery terminal fuse blocks.

                      Comment


                      • #12
                        Saw those, I just enlarged the picture and one says 200A and one 40A, is this what their rated, listing says nothing I could find.

                        And can they be reset on site without replacing parts?

                        Thanks
                        Last edited by Carv; 05-15-2017, 02:30 PM.

                        Comment


                        • #13
                          It's not at all clear from the Amazon ad, but they don't come with fuses...

                          Here's the fuses:

                          https://www.amazon.com/Blue-Sea-Syst.../dp/B0017SJOH4

                          Could also get the single fuse model:

                          https://www.amazon.com/dp/B0019ZBTV4

                          > And can they be reset on site without replacing parts?

                          No, you'd need to replace a fuse. But it shouldn't ever blow, it's just there for an emergency short.

                          Comment


                          • #14
                            Ok I've done a little more digging around here and got some more information: fuses are only to protect the wires from burning up due to over load not to protect the electronics per the site many on here have referred to: http://smartgauge.co.uk/sb_fusing.html


                            With that in mind I think I'm ok fusing the main positive battery cable off the batteries at 150A-175A since the 1/O welding wire I used is rated at 350A (at 50' length & I have a 10' run) (http://www.directwireusa.com/Resourc...IDE%202016.pdf) and my inverter calls for a 200A main line fuse but pulls 125A at max sustained (1500W) and 250A at peak (3000W), and then fusing the MPPT controller at what ever it's rated at before the distribution block.


                            On the system design side I found a great write up by Sun King:
                            https://www.solarpaneltalk.com/forum...battery-design

                            So following this write up:
                            1) Daily usage in watts: My guess at fridge wattage usage is: 1.1A X 115V = 126.5~130W. I estimate my duty cycle time on the high side to be 5 out of every 15 minutes which gives me 20 minutes per hour of run time. So 20 minutes per hour X 24 hours in a Day equals 8Hrs per day at 130W = 1,040Wh.

                            2) Fudge factor for battery & line loss = 1.3. So 1,040 X 1.3 = 1,352Wh per day

                            3) Sun Hour day calculation: Per the solar map where I'll be using the panels in December my factor is 5.0 -5.5

                            4) determine the size of my array: 1,352/5 = 270W is the min panel needed for fridge only.

                            5) Determine Voltage used: "0 to 600 watts = 12 Volts or higher" -I'm using 12V

                            6) Determine Charge controller size 270W / 12V = 22.53A min

                            7) Determine Max charge Batteries can take: I'm running Centennial Flooded Lead Acid (FLA) 6V (GC2200P http://www.centennialbatteries.com /products_golf.html) in series for 12V at a 20A discharge rating of 214 Amp Hours) AH...so C/8 is my max charge (for safety) so...214/8 = 26.75A max charge rating. If I take it down to C/7 charge/discharge rate it takes me to 30.57A. So I would say my max controller amps I should use for this set up is 30A to keep the batteries happy.

                            8) Reverse engineer my max [U][B]usable[/B][/U] panel wattage based on battery capacity : 30A x 12V = 360W so...if I get 1 panel at 330W it should generate 27.5A at the charge controller keeping my batteries happy and lasting long plus give me more than I need to keep the fridge running.

                            Question: If I get more panel wattage than this it woulds just be a waste as it won't charge the batteries any faster based on a 30A max charge rate, it would just be excess capacity I could use for other things BUT based on my usage calculations above I only need 270W of panels to power the fridge so 330W should be enough to run my fridge set up and keep the batteries charged ???
                            Last edited by Carv; 05-17-2017, 07:07 PM.

                            Comment


                            • #15
                              Duplicate
                              Last edited by Carv; 05-17-2017, 06:33 PM.

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