twin 100W panels in parallel, fuse required?

backtrack15 · 12-26-2020, 03:19 PM

I'm planning to put two 100W solar panels in parallel on the roof of my Micro Minnie 2100BH. It has the MC4 connectors pre-installed on the roof with 10-gauge wiring running from there to the designated spot for the solar controller. I know that the 10-AWG wiring should be good for 30-amps, and the SUM of the short-circuit currents for the two panels is 12.5-amps (6.24-amps for each panel). It seems to me that I don't really need a fuse from the panels to the controller since the short-circuit current generated by the panels is well below the limits of the wiring. Do you agree? The general instructions from Renogy seems to suggest I need a 20-amp fuse (short-circuit current * 1.56), but I can't see how it would ever be blown.

I need to go confirm there is already a fuse in the pre-installed wiring to the battery from the controller. A 20-amp fuse there seems like a must.

DavidM · 12-26-2020, 03:28 PM

There is no need for a fuse. As you have surmised the current, even the Isc the short circuit current, will never exceed the 10 gauge capability. Some install them as much for a disconnect as anything, but with MC4 connectors, just unplug.

David

backtrack15 · 12-26-2020, 03:34 PM

Quote:

Originally Posted by DavidM

There is no need for a fuse. As you have surmised the current, even the Isc the short circuit current, will never exceed the 10 gauge capability. Some install them as much for a disconnect as anything, but with MC4 connectors, just unplug.

David

Great. Thank you!

imnprsd · 12-26-2020, 06:06 PM

I would definitely put a switchable fuse as close to battery as possible. This is for safety, but mostly I use it as an "on-off" solar switch for convenience. Your 2 panels put out ~5.3A each, but they go to the solar controller and that puts ~10.6A. but I would use a 20A fuse like this one in the picture.

DavidM · 12-26-2020, 08:14 PM

Yes a fuse in between the controller and near the battery is necessary, but I don’t think that was what the op was asking about.

David

imnprsd · 12-26-2020, 09:42 PM

Yep... I was agreeing with the OP: "I need to go confirm there is already a fuse in the pre-installed wiring to the battery from the controller. A 20-amp fuse there seems like a must."