Forum Discussion

moonlitsouls's avatar
moonlitsouls
Explorer
Oct 09, 2021

Solar Wiring Diagram for Review

Hi guys , hope all is well. Im in the process of upgrading my solar system , with the help of the DIY solar forum online ive been able to create this preliminary diagram but im still a little confused about how the existing ac/dc panel will be wired if im not upgrading the stock /converter charger. A lot of the videos i see online involve switching out the existing charger for a hybrid unit that does inverting and charging , i dont need that. My only goals are :

increase solar capacity
add the dc-dc charger
fuse the system properly

and clean up the install as it was thrown together by the rv dealer who sold the unit to the first owners , thanks a lot for the help

i received this feedback below from someone on the DIY solar forum and i have no idea what he means , pls help me out

"You show no pure dc loads.
That means the only load is the inverter so its kinda pointless to have the connections between the battery and the busbars at 2 awg and then the connection between the busbar and the inverter at 4 awg."


i think my system is designed incorrectly

for reference , this is a thread to the existing discussion on diy solar , any additional feedback would be greatly appreciated

https://diysolarforum.com/threads/pls-help-me-with-system-design.29437/page-4


Truck Campers
  • StirCrazy's avatar
    StirCrazy
    Moderator
    Oct 15, 2021
    ok couple points. they are right, your not showing your DC house loads or taking them into account. run 2 ga to your bus bars from the batteries. all your lights, furnace and so on will draw pure 12V even if you have your inverter on so the largest draw you will experiance is between the batteries and your bus bars. also yes your dc house panel will have to go to the bus bars, ac section will not.. it will come of your auto transfer switch which allows you to switch between shore power/inverter power/dc power. you have a generator also, so you might need two auto transfer switches set up to turn off your charger when using the inverter and alow it to be on when using your genny or shore power.

    I agree with some of the statments about the panels being a weird set up, do you already have them or are you purchasing.. if you havent purchased yet I would look into two larger 24V split cell panels. more efficient and only two to mount, I would look at around the 400 watt each, but I know that room constraints may restrict that.

    Steve
  • reddrum's avatar
    reddrum
    Explorer
    Oct 15, 2021
    Put the fuse on the positive wire as close to the source as possible.

    Fuse 125% of amp rating of load and make sure wire is rated for at least that much.

    Make sure the wiring is large enough to carry the current with max of 3-5% loss in voltage. Use a wiring calculator like the second one on this page to determine wire gauge necessary. Do this for all the pieces. Consider going one size larger than required. Bigger wire, more efficient. From the battery to the bus bars, go overkill with wire size. Only costs a few more bucks, but all the electrons will ultimately traverse these so the more efficient the better.
    http://www.boat-project.com/tutorials/calculator.htm

    You can swap out the guts of the Progressive Dynamics for lithium charging for about $250.

    In a couple spots you have a larger wire changing to a smaller wire on the same path (switch and alternator). I would use the larger all the way through, but regardless, no reason to have part of it larger.

    Personal choice a bit. I would use two smaller solar charge controllers and split the panels across them. Gives some redundancy and can help with shading as well. But, a bit of personal choice there.

    With 800w of solar you could probably skip the alternator connection if you wanted.

    Larger inverters use more power with no load so use whatever size fits your needs. ;-)

    Looks like a fun project and a nice power system.
  • c_traveler2's avatar
    c_traveler2
    Nomad
    Oct 10, 2021
    moonlitsouls: other poster have covered many of your issues, I just have a question. Are you going to start your house generator with a LiFePO4 lithium battery?
  • pianotuna's avatar
    pianotuna
    Nomad III
    Oct 09, 2021
    CA Traveler,

    My panels have diodes between each cell. I went series parallel for a nominal system voltage of 33 volts.

    Many panels only have 3 diodes per panel. I would not feel comfortable with 4 200 watt panels in series. Series parallel i.e. 2 in series and both strings in parallel is a bit safer.

    -30-
  • CA_Traveler's avatar
    CA_Traveler
    Explorer III
    Oct 09, 2021
    The 6 ga wire and breaker might not be adequate. Wire ga is dependent upon the wire length and accepted voltage drop.
  • moonlitsouls's avatar
    moonlitsouls
    Explorer
    Oct 09, 2021
    CA Traveler wrote:
    pianotuna wrote:
    The dc breaker from the solar panels is too small. If my batteries are hungry I get 17 amps from 256 watts of panels.X2 You have the potential of 60A+ maximum on the controller output.

    The wire from the solar panels is on the small size unless all four panels are in series (which I do not recommend).He said series connection. IF his panels have bypass diodes then serial has shade and wiring advantages and hence I'd recommend it.




    hey the 16amp breaker from the panels to the scc is because im wiring them in series , max amps will be 10
  • moonlitsouls's avatar
    moonlitsouls
    Explorer
    Oct 09, 2021
    CA Traveler wrote:
    I think he’s saying you don’t show the remaining house loads and the expected amps. So it’s inconsistent to show 4 ga and 2 ga on either side of the Blue Seas/switch. If the house loads and charger are connected to the Blue Seas switch then the different wire size would be more consistent than if connected to the busbars.

    You can certainly have separate charger and inverter vs a combined unit. Just make sure your charger is adequate for the battery. I would question that as Li batteries are different.

    Not sure why you show the gen, as I’d likely just show charger and it’s DC output to the house loads and how it connects to your diagram. Ie Your panel may have AC and DC in one physical panel but they are electrically separate (except for common grounding).



    thanks a lot. i have a progressive dynamics 45amp charger / converter , but im hardly ever connected to shore power

    i am still unsure about how the dc loads are connected.

    currently there is two sets of wires being routed to the battery positive and negative of the dc circuits , one set is from the SCC , but im going to rereoute that back down to the battery. It was installed this way by the RV dealer because it was seemingly easier for them to avoid having to wire the extra few feet to the battery compartment

    i think the other two positive and negative wires come from the battery itself , but im going to take it apart and figure it out


    once i figure this out , maybe then i can rewrite the diagram accordingly?
  • CA_Traveler's avatar
    CA_Traveler
    Explorer III
    Oct 09, 2021
    pianotuna wrote:
    The dc breaker from the solar panels is too small. If my batteries are hungry I get 17 amps from 256 watts of panels.X2 You have the potential of 60A+ maximum on the controller output.

    The wire from the solar panels is on the small size unless all four panels are in series (which I do not recommend).He said series connection. IF his panels have bypass diodes then serial has shade and wiring advantages and hence I'd recommend it.
  • CA_Traveler's avatar
    CA_Traveler
    Explorer III
    Oct 09, 2021
    I think he’s saying you don’t show the remaining house loads and the expected amps. So it’s inconsistent to show 4 ga and 2 ga on either side of the Blue Seas/switch. If the house loads and charger are connected to the Blue Seas switch then the different wire size would be more consistent than if connected to the busbars.

    You can certainly have separate charger and inverter vs a combined unit. Just make sure your charger is adequate for the battery. I would question that as Li batteries are different.

    Not sure why you show the gen, as I’d likely just show charger and it’s DC output to the house loads and how it connects to your diagram. Ie Your panel may have AC and DC in one physical panel but they are electrically separate (except for common grounding).
  • Lwiddis's avatar
    Lwiddis
    Explorer II
    Oct 09, 2021
    Never using more than a 1000 watts is exactly pianotuna’s point. Inverters should be sized for 1 1/2 times the max expected load for longest life IMO.

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