Solar Panel Roof Wiring

The image above (larger version) shows my planned solar panel wiring that will be on the roof of the RV.  I wanted to work out exactly which connectors, how many, and what wiring methodology I wanted to use, plus exactly what parts would be needed.

The complete parts list is as follows:

This setup will allow me to wire the panels in parallel, giving me the best efficiency when one or more of them is partially or completely blocked.

With this amount of solar (1,700 watts) and my planned battery capacity of around 5,000 watt-hours, it’s possible to fully charge the batteries in one day if I get 3 good hours of sun.  At some point I’ll upgrade to a higher capacity battery bank, but that gets very expensive very quickly.  If I’m not running the air conditioning, the 5,000 watt-hour battery bank should last me at least 2 days assuming there’s no sun at all.  I’m figuring some days I’ll get lots of solar power and completely fill up the batteries, other times it might be cloudy for several days in a row and I might need to run the generator from time to time.

I’ve added an inline fuse for each panel.  It this technically necessary?  No.  And, I somewhat question even how a panel would cause excess current in any situation.  The only somewhat valid reasoning I found online is if, when wiring, some wires cross that shouldn’t, the fuse would prevent things from getting too bad.  Perhaps there are actually other reasons as well.  I decided to play it safe on this one, given how much the panels themselves cost and spend the extra $45 on a set of 5 inline fuses.

Someday I’d love to buy a mega-capacity lithium-ion style battery pack.  It would be smaller, lighter, more durable, and have a much larger capacity for the equivalent size and weight.  But, the prices just aren’t there yet.  I’m planning on spending $500 (not including taxes, shipping, or who knows what else) to get an old-fashioned filled lead-acid battery bank whereas the high-tech lithium stuff was going for around $6,000 for the same watt-hour capacity.  Maybe in a couple years when it’s time to replace the first battery bank the new tech will be cheaper.

Something I’m still working on is whether I’m going to use 10 gauge or 8 gauge wire.  I’m not sure what size the MC4 connectors can handle, nor have I dug into whether that upgrade is really necessary, but I’ll probably go with 8 gauge anyways.  The cost is basically the same, so as long as it fits, that’s what I’ll do.

I’m also not sure if the z-bracket feet will go on the long or short edges of the solar panels, that’ll be up to how well they actually fit when I start placing them on the roof.  If I can mount them on the long edges, I will, but that would increase the space between the panels, and I’m at a premium for space in that direction of the roof.

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