Everything electrical.

Our specs.

Before we get too far into the details, here is a general overview of the electrical components we put into our skoolie.

Our electrical playbook.

The most helpful tool I’d recommend to anyone trying to DIY their own electrical system is to first create an electrical diagram. This diagram should contain all the major components (batteries, charging methods, AC/DC loads, etc) as well as what cables & fuses are needed to connect the system.

Our system had 3 ways to charge our battery bank (solar, DC-DC charger, & shore power) and 2 ways we’d use that power (DC devices & AC appliances).

Credit: Blue Sea Systems [source]

Wires and fuses.

Knowing how to properly size your wires and fuses is a crucial first step before anyone starts their electrical build. Improperly sized wires can overheat and start fires – especially when coupled with incorrect fuses.

The wires are there to transport the current between your batteries and device. The two most important factors when choosing a wire is the cable thickness (gauge) and length. A thicker cable allows more current to pass through and a shorter cable reduces the amount of resistance. Luckily, you really don’t need to be an expert on electronics to size your wires. The above was our go-to cheat sheet we referenced throughout the entire bus conversion.

The fuses act as a safety precaution if a short were to happen. Fuses are designed to handle just a little bit less current than your wires. That way, if a ground connection were to happen, the fuse will burn up before your wire does. To calculate your fuse size, simply multiply the expected amps by 1.25. For example, a 40A DC-DC charger would need a 50A fuse on it’s output side (40A x 1.25 = 50A). When in doubt, always refer to the device’s manual – they usually spell out the suggested cable & fuse sizes.

The short of it is (no pun intended), every positive cable should be fused.

Inverter and batteries.

  • Your inverter, while never 100% necessary, will be your bridge between ‘camping’ and ‘tiny home on wheels’. With an inverter, you’ll get to bring in comforts to your build such as AC outlets, house-hold appliances, and laptops. The batteries you select will provide the necessary power to support your electrical system. Bigger electrical needs means bigger batteries.

    Inverters usually come in standard 1000W, 2000W, & 3000W sizes (larger sizes do exist, though in our experience, 3000W is likely the largest you would need). To size your inverter, add up all the watts of every device/appliance you plan to bring into your build and have the chance to run at once. Choose an inverter size that is at least that number, giving some wiggle room for safety.

    For example, these are the devices we planned to bring into our bus build: A microwave (900W), rice cooker (300W), flat iron (300W), 2 laptops (160W), and a TV (80W). Totaling 1740 Watts. Therefore, a 2000W inverter would be the perfect match (In our case, we opted for the 3000W because we thought we might add on a small air conditioner in the future).

  • Sizing your batteries is just a tad more complicated since you have to consider your average usage over the entire day. Batteries are usually advertised in Amp-Hours (Ah), which indicate how many Amps a battery can provide over one hour. A laptop that draws 60W (or 60W/12V = 5 Amps) can run off a typical lithium* 100Ah battery for 20 hours. The problem is, your laptop does not pull 60W for 20 straight hours. It has it’s own battery and will stop charging once it’s full. Other devices are similar. An electric stovetop will only draw while it’s cooking and your lights only when you’ve turned them on.

    *Quick side note when browsing batteries – there are two main types you’ll likely encounter: lead acid and lithium. This topic gets complicated quickly, as there are many differences between the two (charging voltages, temperature constraints, # of cycles, composition, DOD, etc), but I believe the following to be the most important difference to your typical DIYer. Lead acid batteries should only be discharged to 50% to avoid damage to the battery. Lithium batteries can be discharged to 0% without major damage done to the battery. This essentially means you get twice the capacity with a lithium battery over a lead acid (100Ah of lead acid would only mean 50Ah of usable capacity).

  • There are 3 main ways to charge your battery bank: solar, DC-DC charger, and shore power. You can choose to implement all of these or even just one. We opted to have all 3 in our skoolie build.

    Solar: The size of your rig will primarily control how many panels you can install. I would recommend at least 200W at a minimum (although more is always helpful!). For reference, we insalled 600W of solar (x6 100W) on our bus roof and could go several months without having to pay for a campsite to recharge our batteries.

    DC-DC Charger: A DC to DC charger allows you to charge your house batteries from your vehicle’s alternator as you drive. The charger will control the amount of charge going into your batteries and, when set up correctly, will only turn on when your engine is on. They typically come in 20A, 40A, & 60A sizes. Our school bus had a 200A alternator so we paired it with the 40A DC-DC charger.

    Shore Power: A shore power inlet allows you to plug your rig’s batteries up to any household outlet or campground receptacle in order to charge your batteries. The common options are 15A, 30A, and 50A. The smallest, 15A, is equivalent to your typical household outlet while 50A outlets are usually used in large RV’s with 1-2 air conditioner units. We personally chose the 30A option and bought adapters to allow us to plug into the other two options (a 30A to 15A and a 30A to 50A adapter).

    Note: This option is only available if you chose the Inverter/Charger device or some equivalent. An inverter on it’s own will not have the option for a shore power hookup.