Solar panel fuses & Diodes

[onenyala]

Due to wiring up the diodes on an 18w solar panel incorrectly to two 12v batteries when one of the cells in one of the of the batteries shorted out the other battery kept transferring juice into the dud battery until they were both flat. I think I have now wired the diodes up correctly......
My question is: Does it make any difference which side of the diode the fuse is located ie on the battery side of the diode or the solar panel side of the diode?
Despite the incorrect wiring until one of the batteries shorted out for eight years the solar panel has kept the batteries fully charged.
Other than engine start (Beta BZ482) I have only instruments, tiller pilot and lighting.

 

[VicS]

Put the fuse as close to the battery connection as possible. Any wiring between the battery and the fuse will not be protected by the fuse

 

[William_H]

Diodes and fuses

In fact if you fit the diodes at the battery +ve terminals you don't need fuses.
The fuse is to protect wiring from high current (fire) this can only come from the battery. Unless you have huge solar the solar can not melt the wire with high current.
So a diode at the +ve battery terminal will stop any current flowing from the battery to any potential short circuit.
The diodes should give isolation from the 2 batteries provided the battery switch is off. Or at least not on "both" However one dud cell in one battery will still pull the solar voltage down to the point where the good battery will get none. So check battery voltages good luck olewill

 

[charles_reed]

I'd concur with both posters but would suggest you check the diodes still work - my experience is that reverse polarity kills them.

I have a 15 amp fuse between solar panels and MPPT controller, but then mine feeds in @ 24 volts and I'm relying on the internal protection of the MPPT controller.

My total PV panels amount to 318 watts, nominal. The most I've ever seen is 18.8 amps into the batteries, in Greece, but the input is always @ 1v above system volts.

 

[VicS]

I'd concur with both posters but would suggest you check the diodes still work - my experience is that reverse polarity kills them.

I'd agree with that.

Perhaps you should explain how how you wired the diodes initially and how you have them wired now.

Normally there would be a diode in the positive lead from each solar panel. If one was reversed you would get no charging from that panel and at night you would loose some power from the battery via that diode and panel.

If both were reversed you'd get no charging from either panel.