ouR escaPOD mods

I just installed one in the extension cable that I made. It is going to be closer to the panel when it is in use. That will be a 10A fuse. I had a 60A breaker next to the battery, but had to remove it when it apparently went bad. The converter I installed charges at 50A, so the 60A breaker should not have tripped. Then it was tripping at 40A, 30A, etc. before I removed it. The alligator clips that came with it had a 10A inline fuse. My Renogy suitcase is 100 Watt and the Isc rating is 6.1A, so the 10A fuse should be okay.

Got a solar wiring question for you experts. Wiring up my Renogy Suitcase and thinking about fuse placement. Normally you want fuses close to the power source (battery). But isn’t the solar panel the power source in this case?!? So I’m trying to understand the logic here. Thanks

If you can find an inexpensive source for two conductor SO cord that would be ideal, fine stranding so very flexible with nice thick insulation. But an extension cord is generally going to be cheaper.

There are two criteria you have to look at when sizing conductors. First is ampacity, which deals with safety, the second is line resistance losses, which deals with efficiency. For 120Vac household circuits you rarely have to worry about line losses, but at 12v it’s a major issue.

So, starting with ampacity, the NEC requirement for solar is to multiply module Isc by 1.56 and select a wire and fuse combination with an ampacity higher than that. Why 1.56? 25% for current enhancement from edge of cloud effects and another 25% to avoid nuisance fuse blows. 1.25x1.25=1.56. Is that conservative? For sure, but being conservative is how the Code keeps us safe. So for ampacity purposes with your module, 6.1x1.56=9.5A so you can use a 10A fuse and a 14 gauge cable. In theory you could even use 16 gauge but the code doesn’t allow for field wiring with conductors smaller than 14.

On to voltage drop. General rule of thumb is to keep voltage drop from line resistance to less than 5% or in our case 0.6V. at 12V. You can use one of many free online calculators to find your voltage drop.

In this case you can use your Imp of 5.7A as that is normal operating current. At 50 feet you get 0.57V loss with 10AWG. For 12AWG it’s 0.91V which is getting pretty high considering that there are additional voltage losses in the connectors, fuse and fuse block, etc. Nothing stops you from doing it though, it will work and be safe, it’s just not considered best practice. If you parallel the ground conductor with the neutral the loss with 12 would be 3/4 of 0.91=.68V which you might just call good enough in the interest of keeping cost and weight down.

Back on the fuse, since 10AWG is good for 30A you can use a fuse rated higher than 10A, the upper limit is probably 15A as that is typically the fuse rating of most solar modules.

Hope this long explanation makes sense.