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Solar Project: Figuring Out the Wiring

In my last solar project update, I showed you the battery box Dan came up with. The batteries and charge controller are now installed in the box, so the next step will be connecting all the components together.

For that, we need various sizes of cables and circuit breakers.

To understand how it all fits together, I drew a diagram.

You should be able to click to biggify.

Cable size is based on current (amperage), so they become progressively larger as the electricity travels from source to use.

I used the sizes recommended by Prepper's Total Grid Failure Handbook and the charge controller user manual.
  • 10 AWG from solar panels to charge controller
  • 2 AWG from charge controller to battery bank
  • 4 AWG golf cart battery interconnect cables between batteries
  • 1/0 AWG from the battery bank to the inverter

The manuals helped me size the circuit breakers too.

Solar is a direct current (DC) system, so all of these are DC circuit breakers. Household (AC) circuit breakers are not recommended.
  • 30 amp (12-72 volts) between solar panels and charge controller. The formula is the PV array's short-circuit current (LSC) multiplied by 1.56. The LSC is listed on the back of the panels. For us, that was 6.39 x 3 panels = 19.17 x 1.56 = 29.9 or 30 amps.
  • 60 amp circuit breaker between the charge controller and battery bank was recommended in the charge controller manufacturer.
  • 175 amp circuit breaker between batteries and inverter was recommended in the inverter manual.
They are marine breakers, so they are waterproof. Even though they will be installed in the battery box, that still seemed like a good idea.

All of that is probably more technical than you're interested in, but I want to have all the information where I can find it. That's in case we need it for future reference. A blog comes in handy for things like that!

The next step will be grounding the system.