Solar Panel

[weephee]

Is it necessary to fuse the output of the controller to the battery bank on a 12 volt system. The battery bank is liquid acid

[markcouz]

It should he fused close to the battery, about 125% of expected controller output.

The controller is current limited so doesn't need to be fused, but the battery can provide "unlimited" current, so you are protecting against a short in the wiring that the battery could provide current into.

[sailingharry]

Originally Posted by markcouz

It should he fused close to the battery, about 125% of expected controller output.

The controller is current limited so doesn't need to be fused, but the battery can provide "unlimited" current, so you are protecting against a short in the wiring that the battery could provide current into.

Our installation has individual MPPT controllers for each panel. The controllers are all on a panel and they all feed through short wires to a blade fuse box. The output of that box is a heavy wire that feeds to a heavy fuse at the battery bus.

As Mark says, these are all fused at the battery end of each wire, because the concern is not an overzealous solar panel, but some sort of fault that leads to current flowing the other direction.

[weephee]

Thanks for your replies. I now understand

[hlev00]

Though you didn’t ask, you do not need fuses / breakers on the panel side as long as the wires are sized properly. You should have switches to disconnect the panels from the controllers instead of relying on the MC4 connectors. Or cover the panels before connecting / disconnecting the MC4s.

[noelex 77]

Originally Posted by hlev00

Though you didn’t ask, you do not need fuses / breakers on the panel side as long as the wires are sized properly. You should have switches to disconnect the panels from the controllers instead of relying on the MC4 connectors. Or cover the panels before connecting / disconnecting the MC4s.

You don’t need fuses/circuit breakers on the panel side if you only have one or two panels, but circuit protection is required if you are installing three or more panels in parallel.

This is in addition to the always required circuit protection between the controller and the battery.

[hlev00]

Originally Posted by noelex 77

You don’t need fuses/circuit breakers on the panel side if you only have one or two panels, but circuit protection is required if you are installing three or more panels in parallel.

This is in addition to the always required circuit protection between the controller and the battery.

And I believe in the 3+ parallel configuration each panel needs protection to prevent the others from dumping current above the faulted panel’s design capacity.

[noelex 77]

Originally Posted by hlev00

And I believe in the 3+ parallel configuration each panel needs protection to prevent the others from dumping current above the faulted panel’s design capacity.

Yes, that is correct .