Is panel negative return wire needed?

For a remotely located panel (50 feet away from cabin), I've always wondered if the negative side of the panel could simply be grounded near the panel, saving the cost of heavy wire to the batteries in the cabin. I would retain the grounding rod connected to battery negative at cabin. Anything wrong with that?


  • BB.BB. Super Moderators, Administrators Posts: 33,327 admin
    Re: Is panel negative return wire needed?

    Not really possible for many reasons...
    • ground resistance is too high
    • Solar PV Panels are DC--You will have electrolysis causing the ground rods to corrode and if there are pipes/buried metal in the ground--they will quickly corrode too.
    • If you have lightning in the area--You will get hundreds to thousands of volts between the two points in the ground and blow out your hardware.
    The solution for saving on copper wire is to wire the solar panels in series to jack up the voltage and reduce the current.

    Power = Volts * Current... So if instead of 15 volts charging the battery bank, you wire up 6 panels in series, you now have >90 volts going to the solar charge controller (MPPT type) and can use 1/6th the thickness (and cost) of copper wire.

    One of the neat things about MPPT charge controller is they can efficiently take high voltage / low current from the solar array and "down convert" it to low voltage / high current to charge the battery bank.

    MPPT type charge controllers and series connected solar panels are generally the solution to long wiring runs.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Is panel negative return wire needed?

    "The solution for saving on copper wire is to wire the solar panels in series to jack up the voltage and reduce the current."

    as well as put the pvs closer to the controller and batteries.

    don't try shortcuts on the wiring as you'll most likely pay a higher price for that down the road with blown out equipment and/or a compromised system that won't perform as expected.
  • MisterBMisterB Solar Expert Posts: 156 ✭✭
    Re: Is panel negative return wire needed?

    Siting the panels as close as possible to the batteries is always best. I live in a full blown off the grid community and there are a lot of systems here that poorly sited, not just because of distance between the panels and rest of the system but because a lot of home owners don't really understand the basics of solar and have their panels on the north side of their building, for example, which means either being in shadow if they are close to the building or a really long wire run if they are far away.

    If you want things to really work, put your panels on a good rack either several feet off the ground or on a roof and put them on the south side of any buildings as close as posible to the controller and battery bank and orient the array along the north south axis if you don't have a tracker.

    I once got a neighbors array to go from around 30 to 39 amps by sorting out some spagetti wiring and convencing them to buy a good rack for their panels.
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