Electricity is a long process from start to finish. This is an element of the skoolie build that needs to happen incrementally over time. We still hadn’t even put our battery bank together when we left Vermont in April. Once finally found some time to finish the process at a friend’s house in Greenville, South Carolina, we were ecstatic. We had been living in the bus with no electricity and the first time it came on was pretty euphoric.
In this post: Bus Wiring Solar Panels Back-Up Camera Ceiling Fan Interior Lights USB Outlets Refrigerator Fuse Box Inverter Battery Bank
Bus Wiring
The electrical work in the bus started early on in the demolition process. We needed to get our bus inspected, but had a laundry list of tasks to complete first. We needed to remove any red flashing lights or at least render them inoperable. As we removed the lights, we decided to remove their wiring just to simplify the rat’s nest of wires. We took time to asses if any of the old wiring we removed could be reused. The easiest way to whittle down the old wires was to disconnect them and trace them back to the power source. This was an arduous process in the beginning as we were trying to be careful not to cut any wires we would still need. Fortunately, it became more simple as there were fewer wires to sift through.
In the end, we removed more than 20 pounds of wiring from the bus. This included the red/yellow flashing lights, buzzers on the emergency exits, interior lights, the auxiliary heater, and the rear speakers. The auxiliary heater was in the back of the bus to keep kids warm through New York winters. It had seen better days. The heater was connected to the engine coolant system, so it always radiated heat and we didn’t have a way to shut it off. The speakers that came in the bus were very cheap and the rear ones didn’t even work. We chose to remove the wiring for the rear ones entirely and upgrade the front speakers to use while driving.
After we removed all of that wiring, we had to reconfigure the remainder that we planned to keep. The original door-opening mechanism had a panel of switches on top of it that controlled the main functions of our school bus (like the red/yellow flashing lights, stop sign, heated mirrors, interior lights, etc.). However, the door-opening mechanism was going to be in the way of the passenger seat we planned to install. We therefore had to disassemble and relocate the the mechanism and the panel of switches.
The panel had 9 switches but after removing the wiring we didn’t need, we were left with 3 that we planned to reuse for their original purpose (interior lights, heated mirrors, and a small DC fan for the driver). We routed the wires behind the dash and shortened them so the switches are easily accessible while driving. We also added a fourth switch next to them for the backup camera installed down the road.
Solar Panels
Soon after the bus was repainted, we were eager to install solar panels on the roof. We bought a kit from Renogy that came with everything that we needed for the setup. The first step was to secure the brackets to the panels. Then we figured out the orientation the panels needed to be in for the wiring to be able to reach. The positive and negative wires from the panels are pretty short, which gave limited options for how the panels could be oriented on the roof.
After determining how the wiring would fit together, we lugged the panels onto the roof, stuck butyl tape to the bottom of the brackets, and lightly stuck them in place to get them lined up. We used the butyl tape to help keep water from seeping under the brackets and leaking into the bus. We then drilled holes through the roof where the brackets were and lined them up with small blocks of wood on the inside of the bus to screw down into. Instead of relying on the small area of contact between the screws and the thin sheet metal roof, the screws now have the blocks of wood to give the panels a much more secure mount. Once the panels were secured to the roof, it was quick work to connect the positive and negative cables together with the Y-connectors and the 10 AWG wires, which were then fed through the cable entry housing. The cable entry housing is a waterproof way of getting cables from the outside of the bus to the inside. All of the solar components were supplied with the Renogy kit.
The 10 AWG wires from the panels run through the wire channel on the inside of the bus towards the back. Here, they are then connected to the MPPT charge controller supplied with the kit. We installed the charge controller below one of our couch seats along with the fuse box. The charge controller has four slots for 10 AWG wire to be secured into: a positive and negative from the panels to the charge controller, and a positive and negative from the charge controller to the batteries. Following the recommendation from Renogy, we used a 30 Amp fuse on the positive wire coming from the solar panels to the charge controller, and another 30 Amp fuse between the charge controller and the batteries.
Our charge controller also has ports for an optional temperature gauge, voltage gauge, and bluetooth module for monitoring the system. The voltage gauge connects to the battery terminals to measure the voltage of our batteries. The temperature gauge goes near the batteries to monitor the ambient temperature around the batteries and make sure they aren’t overheating. The bluetooth module works in partnership with the Renogy app. This allows you to see how many watts the solar panels are taking in, what voltage the batteries are currently at, and the ambient temperature of the battery bank. Now we can soak up the solar rays to charge our batteries and stay off grid for extended periods.
Back-Up Camera
The back-up camera installation was fairly straightforward, especially after we had already installed the solar panels. We purchased a back-up camera with a small monitor from Amazon. We had no idea what the view would look like, or how high it would need to be, so we left the wire long and started by wiring it into the fusebox above the driver seat. Once the camera and monitor had power, we climbed onto the roof to aim the camera while looking at the monitor. We picked an optimal placement on the bus and marked it.
We could have avoided this step by wiring the camera up to its permanent switch in the dash. However, we wanted to make sure it would work for us before we committed to installing it. We then drilled a hole in the roof for the wire to go through, installed a grommet, and then a wire pass-through, which prevents water from getting into the bus.
Similarly to how we installed the solar panels, we used a small piece of wood for the mounting screws to be secured into to give them more stability. We used LAP sealant to seal the edges around the camera and wire pass-through on the roof. We then went back to the fuse box above the driver’s seat and disconnected the wires from the power source. This was so that we could connect the camera to a switch in the dash. This makes it so that the back-up camera is only on when we need it, and not draining the bus batteries when we don’t.
After the camera was connected to the switch in the dash, we reconnected it to the fuse box above the driver’s seat, and mounted the monitor above the driver. Since we mounted it high up on the back of the bus, it gives a great view of the space directly behind the bus. It also shows any branches that might hit the roof as we are backing up.
Ceiling Fan
We cut a ~14″ square in the roof of the bus for our MaxxAir Fan to be installed above our bed. Cutting through the roof of the bus was a stressful process especially knowing we had just patched up any leaks and repainted. Thankfully, it went smoothly enough. We outlined the footprint of the fan on the roof and stuck pieces of painter’s tape along the lines. We used an angle grinder to cut the hole and then sanded down the sharp metal edges with heavy grain sandpaper (wear gloves for this). Next, we pre-drilled holes for the mounting screws, put butyl tape on the bottom of the fan to help it stick down, and secured the fan with the supplied screws. We used LAP sealant around the edge of the fan on the roof and all of the screw heads to avoid any leaks.
On the inside, the wiring that comes from the fan is aluminum stranded 21 AWG, so we re-used some of the 16 AWG wire we took out of the bus to extend the wires behind the ceiling and into the fuse box we installed in our couch seat. Fortunately, our fan has built in controls for power, direction, and fan speed so we didn’t have to wire any switches for the fan.
Puck Lights & LED Strips
We wanted puck lights mounted in the ceiling of our bus, but we didn’t want to have too many to the point where it’s overbearingly bright. Our solution for this was to use a combination of puck lights and LED strips to help diffuse light around the bus and give lighting options. We bought two 4-packs of LED puck lights, but we only planned on using 6 in the ceiling. These lights consume very little power so we reused some 14 AWG wire to run from our fuse box to the front of the bus to a dimmer switch, and then from the dimmer switch up to the ceiling where we taped the wires in place for each light.
We routered out circular holes in the ceiling boards and dropped the extra length of wire through these holes. With these wires hanging down, it was easy enough to use crimp connectors to wire them to the lights and then add heat shrink to protect the connections. Once wired in, the puck lights are tucked into the holes using springs that fold up above the ceiling and then fold down to hold pressure. We chose to wire the puck lights in parallel, so each light has its own designated positive and negative wire. This means that if one of the lights dies, the other five lights will stay on.
For our less intense lighting, we found LED light strips that are dimmable and can run off our 12V battery bank. We found an option online that had 16 foot and 32 foot variations of color changing LEDs that could run off 12 volts. The small catch is that they came with a DC power cord and small converter that plugs into a regular outlet. The job of the power converter is to take the 120 Volt AC power from a normal house outlet and convert it into 12 Volt DC power, which is safe for the LEDs. Since we have a 12 volt system, we don’t need that.
We cut off the converter box and figured out which of the two wires was positive and which one was negative. Although the LED light strips came with a remote to control the power, brightness, and color, we didn’t want to have to track down the little remote when we needed to use the lights. Since we had a few leftover switches from the bus’ original control panel, so we decided to use those for the LED strips. We have one strip that on our passenger side shelf, and another under our kitchen cabinets. The power cord for the two LED light strips were connected directly to their own light switches, and then connected with 14 AWG wire to the fuse box with independent fuses. By reusing these switches, we can turn each light strip on and off with the switch, but we can still use the remote to control the brightness and change the color of the LEDs.
The two unused puck lights we had left did not go to waste! They were installed in their own circuit in the back of the bus under the bed to be used as “garage” lights. We had a leftover dimmer switch so we mounted the lights just below the bed near our water tanks, and wired them through the switch and to the fuse box using 14 AWG wire. Now when we open the back door to look for gear or check our water levels, we are able to see what’s going on in the flick of a switch.
With (1) puck lights to give us bright light when we need it, (2) the LED strip mounted under the upper kitchen cabinets to help us see when we are cooking, (3) the LED strip mounted on our passenger side shelf for mellow indirect lighting, and (4) the puck lights in the garage to help us navigate our storage space, we always have the right lighting for whatever we need.
USB Outlets
To charge our devices more efficiently, we bought four 12 volt USB chargers with two USB slots each. Two of the USB chargers are in the headboard of the bed, one is under the table in the couch, and one is by the passenger door. At first, we thought this was overkill for the size of the space. However, we have come to realize just how nice it is to easily plug things in anywhere in the bus and not have wires all over the place.
The chargers were simple to install and only required a 3/4″ hole saw and a drill to make the mounting hole for them. Since the chargers were designed with automotive use in mind, they come with inline fuses. For our use, we had to wire them into our fuse box anyway, so now they each have two fuses. Each outlet was wired with 12 AWG wire and since they charge from our 12 volt battery bank directly, it’s much more efficient to use these than charging with the inverter.
Refrigerator
Our fridge was one of the things that we bought in advance and didn’t have a way to test it. By the time we got around to installing it in the bus, we were really hoping that it would work without issue. We have a Dometic CRX-65 fridge that runs off 12 volt power so it doesn’t need to use our inverter. We are able to plug it directly into our fuse box like the rest of our electrical system.
We have been pleasantly surprised by both how much we can fit inside of our little fridge, but also how little electricity the fridge draws from our batteries. The fridge comes with a short length of red and black wire off the back of it, so it was simple to splice some extra lengths of 12 AWG wire to them to extend them to our fuse box. There is some extra slack in this wire to give us wiggle room just in case we need to pull the fridge back out, if it ever has issues. Thankfully, once we slid the fridge into its new home and turned on the power, it hummed to life and quickly cooled down.
Fuse Box
The fuse box is the “brains” of the operation with regards to how it takes power from our battery bank and safely distributes it to everything we have that requires electricity. We found a 100 Amp 12 way fuse box that suited our needs well with a little wiggle room for expansion. In the end, we used 11 of the 12 available ports. Our fuse box is mounted within a few feet of the battery bank with 4 AWG wire connecting the positive and negative terminals to their respective terminals on the batteries, as well as a 100 Amp breaker to protect the fuse box. Not only is the 100 Amp breaker a good idea to prevent damage due to high current from the batteries, but it is also a convenient way to shut off the power between the batteries and fuse box when the bus isn’t in use.
Although our fuse box can handle up to 100 Amps worth of power, most of our appliances, chargers, and lights require very little power and we use a fraction of the fuse box’s capabilities. Because we have enough space for things to be on their own circuit, we have independent circuits for all 4 USB chargers, one each for the ceiling puck lights, “garage” puck lights, cabinet LED strip, and shelf LED strip, water pump, MAXXAIR fan, and fridge. We have one open slot if we ever wanted to add anything else to the system. If we ever needed to add more than one circuit, it would be easy enough to pair up the USB outlets to free up a couple more. This fuse box came with stickers to label the circuits and has a small light for each fuse that lights up when a fuse blows or needs replacing.
Inverter
Although we have plenty of options for charging 12-volt electronics, there are times when you need a standard 120 volt AC socket to plug certain electronics into. For these, we have a 1500 watt inverter/charger on the floor below our bed with a small cabinet door to cover it when it’s not being used. The inverter takes the 12-volt direct current (DC) power from our batteries and ramps it up to 120-volt alternating current (AC) so we can charge our laptops or plug in anything with a standard 3-pronged wall plug. Although it’s convenient to be able to plug things into a standard outlet, there is inevitable power loss when ramping the voltage up from 12-volt CD to 120-volt AC. Since we have a 12-volt battery bank, it’s much more efficient to charge any electronics using DC power when possible.
The second function of our inverter is to charge our batteries when we have shore power — that is, when we are at a campground with electrical hookups, our at a house where we can bum some electricity. We can plug an extension cord into our inverter and charge our battery bank. We have solar power to help us recharge on sunny days, but having the ability to charge by another means gives us a fallback in case we hit a string of cloudy days where our solar isn’t as effective.
Although our 1500 watt inverter is relatively small, inverters in general need a lot of power to run. To avoid voltage drop, especially when using a DC system, you should put the inverter close to the batteries. It’s hard to go too big when sizing cables for an electrical system, so to err on the side of caution, we used 2 AWG wire to connect the positive and negative terminals from our inverter to the positive and negative terminals on our battery bank. We have a 130 Amp breaker on the positive wire between our inverter and our battery bank just in case there’s any power surges, and to be able to more easily disconnect the inverter from our power supply if needed. Our inverter also came with a small cable to ground it to the chassis of the vehicle, so we drilled a hole into the seat rail that the old seats were mounted to, sanded down the area around the hole, and screwed a ring terminal tight to the bare metal to ground the inverter.
Battery Bank
To size our battery bank, we needed to estimate how much power we would be using at any given time. We used GoPower’s Solar Calculator (https://gpelectric.com/calculator/) to help us calculate how much power we would need to charge our electronics, keep our fridge running, and power our lights and fan. We want to spend at least a few days off grid at a time, so we tried to size our battery bank for fairly heavy use and no solar input for 3-4 days to give us a worst-case scenario. When sizing a battery bank for lead-acid batteries, it’s important to keep in mind that you can only discharge the battery 50% before the battery starts being damaged.
Using this information, we decided on four GoPower 6-volt AGM batteries with 224 amp hours each. Compared to a traditional flooded lead-acid battery that has a liquid electrolyte that is free-flowing and can spill or might need to be topped off, an AGM battery is sealed and has a special glass mat that wicks the electrolyte solution between the battery plates in order to keep it in a suspended state. We didn’t want to have to worry about our batteries off-gassing, or battery acid spilling in the bus, or needing to be topped off. These 6-volt batteries are also designed with solar charging in mind, so they won’t have any issues being depleted by usage and recharged by the sun each day.
In order to power our 12-volt appliances like the refrigerator, fan, and everything else in the fuse box, we needed to connect two of the 6-volt batteries in series by connecting the positive terminal of one to the negative terminal of the other, and then connecting the remaining positive and negative terminals to each other. By connecting two of them in series, we doubled the voltage while keeping the same capacity, so they will act as one single 12-volt battery with a 224 amp hour capacity. As we mentioned before, having a 224 amp hour capacity means you essentially have about 112 amp hours of functional power before the battery charge is too low and will do irreparable damage to the batteries.
For a larger capacity, we connected the other two 6-volt batteries in series just like the first pair, and then connected both pairs of 12-volt batteries in parallel by connecting the positive terminal of one pair to a positive terminal on the second pair. By connecting them together in this fashion, it maintains a 12-volt charge but doubles the capacity of the battery bank to 448 amp hours. This allows us to stay off grid for longer and not stress about draining our batteries every day. We used 2 AWG wire we sourced from Lowe’s to connect our batteries together. We made sure all of cables were the same length, cut 5 lengths for our batteries, stripped the ends, and used a heavy-duty terminal crimp tool to crimp lugs onto each wire. Although this wasn’t a particularly challenging task, it was fairly time consuming and laborious. When hammering lugs onto heavy gauge wire, it’s important to plan the orientation of the lugs before crimping them on because thick wire can be very rigid and unforgiving when you’re trying to bend and twist it into position later.
Once all four of our batteries were hooked together, we used a voltmeter to double check the voltage across the poles (from the negative pole of the battery at one end to the positive pole of the opposite battery at the end) to make sure we had an appropriate voltage for a healthy 12-volt system. We then hooked up all of our positive connections (i.e. fuse box, inverter) the the positive pole of one end of the system and all of the negative connections to the negative pole on the other side of the battery bank. Using the positive terminal from one battery and the negative terminal on the opposite side of the battery bank allows for a healthier flow of power through all 4 batteries when they are hooked up in series and parallel, and allows them to drain and recharge more evenly.