This is a big, tricky topic because it’s going to be different for everyone. I’m going to take you through what I did, and show you the tools you need to build your own electrical system.
1) List all of the things you want to run that draw power. Make a big list, be thorough.
My list looks like: 12 V DC Fridge, vent fan, projector, LED lights, charging ports, speakers
2) Next to each item in your list, write out it’s power consumption in Watts. This information can often be found on
power cords, manuals, etc. If it only gives you the current, you can find out it’s power draw with the formula: Power
(Watts) = Voltage (12V usually) * Current (Amps). Worst case, make an educated guess
3) Now think about how long each day you will run each appliance. Write it down next to it in hours.
4) Calculate the Amp-Hour draw of each appliance, write it down, and total it up. Double it. Now you know how many Amp Hours your battery should have.
Note: You double it because batteries really should only be run down to 50% when you can help it, otherwise your battery lifetime will be very short I bought a 100AH AGM battery for my
setup, and it works well. Two batteries and I’d never run out of power, but I’m on a budget. You want to get a sealed,
preferably AGM battery for safety and for better performance on “slow” power draw. Don’t use a starter battery! They can off gas and aren’t meant for running appliances. Some people use a lithium battery bank, but it
adds cost and complexity.
5) Draw out an “Electrical Diagram”. I like to also position the appliances about where they’d be in the van because it
also makes a good blueprint when you install everything
The “Control Panel”
You can certainly make your own control panel with switches and fuses. I opted to buy one pre-made that was intended for
boats. It was cheap, and gave me a nice looking panel of switches with replacable fuses so that I could do a lot less work. Wire every appliance through a fused switch, so you can power it off, replace it’s fuse, and measure it’s current easily if you need to.
Wire everything up!
Make sure to use the right gauge wire for the estimated power draw from your plans and for the length the wire will
be (Handy Calculator). If the wire isn’t thick enough, you won’t deliver enough volatage to the intended appliance and it will run poorly (or not at all!). If the wires are all too think, you increase your cost, and they are unnecessarily hard to work with.
Make sure your wires won’t rub up against any van metal to potentially prevent shorts. Remember each appliance will need a power AND ground wire to the battery (sized the same). Don’t rely on chassis ground for your house appliances, that will cause problems.