12v Solar Diagram for RV

[parnsnips]

Hey! This is my diagram for my RV solar power system. I know the 6AWG from the panels to the charge controller and controller to battery are higher than the panels would call for, but hoping this will accommodate additional panels in the future. How's this look? Any feedback appreciated.

Thanks

[bob-n]

That's an interesting plan. I'm worried about that 100A battery fuse and wire size to the battery.

If it's night and the inverter is working hard, supplying 1kW to some load, it is consuming high current from the battery. Assuming 92% efficiency at 1kW, that means it is pulling 1087 watts at 12V so drawing 90.5 amps. But at 1kW, it is putting out less than 12V. Also, as the battery starts to run down, the voltage will drop even lower, resulting in even more current. Assuming 11V, that would be 99A. To make things worse, there is also voltage drop in the wire and the terminals.

Oddly, as the voltage drops, the inverter will draw MORE current so it can get the desired power. We call that negative resistance. Academics think it's elegant, but engineers find it challenging.

If someone then turns on a 12V load in the RV like the headlamps, that could pop the 100A fuse.

It might be more robust to connect the fuse box to the battery through a second fuse rather than running everything through the 100A fuse.

One other issue is that AWG 6 copper is too skinny for 100 amps. Most people require AWG 1 for 100 amps. Shorter lengths and lower air temperature may allow you to use AWG 2, but not AWG 6 (37 amps max). If you are using aluminum wire, you need to go even fatter, typically 2 gauge numbers. Aluminum wire also requires special connectors, so avoid it if at all possible.

Reconsider the size of each piece of wire and the voltage drop down the cable. This table will help:

https://meters.co.uk/american-wire-gauge-awg-cable-conductor-sizes/

[chrisski]

For this ampacity chart, 6 AWG won’t make 100 amps. Probably want 2 AWG or 1 AWG. THe wire could go before the fuse with 6 AWG.

37FE0B28-62BC-4928-BBC6-756167E557DE.jpeg
I don’t really like the idea of 6 AWG from the solar panels. It’s more of a connector thing than the wires too thick. Most solar panels come with MC4 connectors, so those are only rated for 30 amp and 10 AWG and smaller. You can buy some pre-made 8 AWG MC4 connectors, but the MC4 connector still has a 30 amp limit.

6 AWG is good for certain things like if you plan on running between 50 and 75 amps in an upgrade, you could certainly wire it that way. You just need to figure a way to splice from whatever you come out of the MC4 connector such as 10 AWG wire to 6 AWG. That could be a combiner box with a dingle connection. A Gangbox like this could work to combine some strings:

1F1FAB7E-9C20-42E5-845B-2E6659029A5E.jpeg
I also thing that going higher in voltage can be better than higher amperage.

[GeorgeF]

1 x 100Ah with 1000w inverter? Perhaps you can consider to have DC-loads only.