Fuses in parallel array

Re: Fuses in parallel array

Okay? Yes. Recommended? No. You should have a fuse per panel for the four you've got now just to be on the safe side. But a 60 Watt panel has an Isc around 4 Amps so it may not be that easy to find good fuses that will work.

I wouldn't be too worried about it.

Output from all six panels through the controller will be around 20 Amps using PWM type and typical Vmp of 17.5. Definitely you want a fuse there because the battery can dump a lot more current than that through the wires should something go wrong.

Re: Fuses in parallel array

When paralleling panels the only arrangement that works is one fuse per string. You can't put two together in parallel and fuse them and then two together in parallel and fuse them. Here's why:

What you are protecting against is the possibility that one panel may short, allowing it to be fed the combined Isc of the remaining panels that are in parallel. You never know which panel may short, and if it's one of a pair and the fuse protection is on the pair then the fuse doesn't blow and the current from the non-shorted panel adds to the current from those 'on the other side of the fuse'. That is to say no protection is provided whatsoever.

Ideally you will have a number for "maximum series fuse rating" on the panel. This is the most current it can take as a conductor (shorted). It is usually 15 Amps on larger panels, but may be 10 Amps or less on smaller ones. Failing the availability of that number you can use the Isc rating sized up to the nearest available. So if the panel has an Isc of 4.1 a 5 Amp fuse will probably suffice.

This problem occurs very rarely, but if you want to cover all bases there it is.

As for the output side you have a 30 Amp controller which will not be maxed by the panels so a 30 Amp fuse will handle that and should pop before anything else in the event the controller shorts. The wire size here should be at least 10 AWG to make sure it doesn't burn before the fuse goes.