Wiring questions for solar and bed run fuse box?

Hey everyone, wiring is not my forte and when it gets into running larger wires I start getting confused.

Here’s a quick schematic of my wiring idea for solar and a bed based fuse box off my offgridengineering dual battery set up and I just have some questions.

1. Will 4 gauge wire be big enough if I want to run a fridge, USB ports, possible inverter, possible small space heater?

2. I have no idea what size circuit breaker and/or fuse to plan to use for the run of cables to the bed. Any suggestions?

3. My solar panel kit is the renogy 10 amp 100 watt solar kit. It comes with 12 gauge wire to run to the battery. I’m going to run this to the aux battery and since it’s only a 10 amp kit it’s suggested to use a 10 amp fuse between the battery and the controller. Is this correct?

 

First your wire size and circuit protection are determined by the size of your loads .

Wire size bigger is better in most cases. circuit protection smaller is better it opens faster .

Your drawing is interesting

 

Yeah definitely not an artist

Problem is I currently have no idea what kind of amp draw the bed will require so I am just trying to get a set up going that will cover the bases. I'm torn between 4ga and 2ga wire because the run from the front of the truck to the bed is
only going to be about 15 ft max ( guesstimate since Im running from the battery down the engine bay down the frame and up into the bed ). 4ga will cover it as long as I don't go above 150 amps, if I do it needs to be 2ga.

I dont have access to a ARB fridge or its instructions to see whats required for them and I can't find it online. So was hoping someone thats done it before could help me out.

Size of the circuit breaker is going to depend on that info also.

And I was curious about the 12ga wire that comes with the solar charger because its prob a 10ft run from the cab where I want to mount it to the aux battery which should put me in a good spot but wasn't sure

 

Two big things to consider,

what size inverter?
What size heater?

most space heaters (even the little tiny ones) pull a massive amount of power. The typical small space heater will be 750w in low and 1500w on high.
So at 12v, that’s 63A current draw. Even a huge 120ah deep cycle battery will be drained in an hour on low, 30min on high.
And again, that’s IF you had a giant deep cycle as your 2nd battery, which most people don’t.

same power draw concept goes for the inverter. If you want a big inverter, it’s a power hog.
*additionally, the space heater will be powered by the inverter, so add in a good chunk of extra power draw that will be lost through inverter inefficiencies. This also means you need an inverter large enough to power the heater.

 

Power = Volts * amps


That's about the only equation you need to calculate how much load you've got. Make yourself a spreadsheet, add it all up, add some extra breathing room, and then you can use a chart to know exactly how heavy the wire should be. Beats the hell out of guessing.