***MEGA DISCLAIMER: I am not an electrician. Am I an electrician? NO! I am NOT an electrician. If you are wiring a skoolie and you want professional quality electrical work hire an electrician. Could you hire me to do this? NO! Why? Because I am NOT a licensed electrician. If you read another blog or watch a video made by a licensed electrician and they say something that contradicts what I say, should you trust me? NO! You should trust the licensed electrician! That being said…
You might say that this section is in truth the whole reason I am writing this blog. I have basically no experience with electrical wiring and equipment except for a couple physics classes in High School (and we all know how little of what we learn in High School actually sticks). I spent countless hours pouring over hundreds of different skoolie, RV, and electrical blogs just trying to figure out what the hell was going on. I had to google basically every term I read. I couldn’t figure out what parts I needed. I couldn’t figure out what size of those parts I needed. I definitely had no idea how to actually put things together. Luckily for me my dad happens to be one of those miraculous people who seems to know something about everything and is generous with both his knowledge and time. During my spring break from nursing school, he taught me what the blogs did not and without him I never could have done the electrical system myself. However, not everyone has a handy dad like this. So my goal is to write the blog entry that I would have needed – one place with all the info necessary to wire a skoolie, explained simply and with pictures. It’s going to be a very long post so I will bold some of the most important info. So, here we go.
First you need to know the difference between 120 volt electricity and 12 volt electricity. 120 volt electricity is the type of electricity used in your house (sometimes referred to as 110 volt, for our purposes it’s the same, don’t get confused). 12 volt electricity is the type of electricity used in your car battery. Keep these two in mind, since they’ll become important later.
1) Sources of Power
Every skoolie needs to have a source of power if you want to run anything electrical. There are a few options and many skoolies use more than one option. Here are some:
A) Batteries – we’re not talking little AAA batteries, we’re talking about a 12 volt battery the size of a car battery or bigger. Most all skoolies need to use batteries as a source of power and importantly to store power.
Type: RVs and skoolies use what are called “Deep cycle” or “marine” batteries. Your regular car battery is meant to do that quick burst to help you start your engine. Deep cycle and marine batteries are meant to provide power over a long period of time. You want one of these, NOT a regular car battery. A bunch of skoolie bloggers will insist there are important differences between “deep cycle” and “marine” batteries. Honestly, in my opinion don’t worry about it, especially since many batteries are labeled as “deep cycle/marine” anyways.
Size: The important unit that measures the size of one of these batteries is “amp-hours” abbreviated Ah. An amp is a measure of how much electricity required to power something. An amp-hour is measure of how long you can power it. So, if I have an electrical blender that requires 2 amps to power it and I have a battery with a capacity of 100 Ah, I can use that battery to continuously run that blender for 100/2 = 50 hours (why you would want to do that, I don’t know). However, your everyday appliances don’t say how much electricity they need in amps (A), they say it in watts (W). For example, take your typical household “60 watt bulb.” It requires 60 watts to run, but how many amps? Use this equation:
Watts = Amps*Voltage
This typical household lightbulb requires 120 volts. So…
Amps = 60 watts/120 volts = 0.5 amps.
So if I have that same 100 Ah battery, I can power this light bulb for 100/0.5 = 200 hours. If you have multiple things running they add together. If I want to run 4 of these lightbulbs at once, using this same battery, I can power them for 100/(0.5*4) = 50 hours.
Battery banks and price: You could have one massive battery or you could get multiple batteries and wire them together to make a battery bank (most people do this). When you wire the batteries together their capacities add. For example, if you wire two 100 Ah batteries together, it is the equivalent of one 200 Ah battery. Why use multiple smaller batteries instead of one larger one? Because batteries are very expensive, and the more Ah, the more expensive they are. A 200 Ah battery can cost roughly $250-$350. You can buy two 100 Ah batteries for $100 each and combine them for cheaper.
“How many Ah do I need?” This was the question I always wanted the blogs to tell me the answer to. Unfortunately, it matters on what you plan on running and how often you want to recharge your batteries. Here’s how to calculate it. Make a spreadsheet. In column A put the name of every electronic thing you use. In column B put the watts required by each item. You can use a chart like this one to estimate them. In column C, divide column B by 120 to get the number of amps required (assumes 120 volt appliances). In column D put the average number of hours you expect to run each item per day. In column E, multiply column C by column D. Sum up the total in column E. This is how many Ah you need each day. Next think about how many days you want to be able to go before recharging the batteries. If I want to be out in the middle of the desert for 3 days without recharging my batteries I should multiply my sum by 3. And lastly multiply your final number by 2. This is because you never want to fully discharge your batteries down to zero (it makes the batteries very sad and not work well), you only want to discharge them about halfway before recharging them.
“Golf” batteries: if you’re reading other skoolie blogs you will likely come across people recommending using “golf” batteries which are 6 volt batteries instead of 12 volt. If you wire them together in a certain way (in series) they function as a 12 volt battery. The advantages seem to be that they are found for good quality pretty cheaply at places like Costco or Sam’s Club. I did not chose to go this route, so I can’t give advice on how to do it.
Since our budget is small and our energy needs small as well we went with only two 114 Ah batteries from Walmart. These batteries have gotten a lot of bad reviews as being low quality from some skoolie blogs but they are cheap, so were giving them a shot.
On to the next power source! A shorter section, I promise.
B) Solar – solar is a super awesome option! You just mount panels up on the roof, run wires through what is called a “charge controller,” down to your batteries and they charge them up all day as long as there is sunshine! Voila! What is the catch you ask? Solar is super expensive. The standard panel I see getting used is a 100 watt panel. Each of these costs about $150 and if you get the kit which includes a charge controller it will be more. The charge controller is basically what keeps the power from the solar panel from overcharging and frying your batteries (you definitely need this if doing solar). Solar panels usually produce 12 volt power so they can charge the batteries which use 12 volts as well. We ended up being the luckiest of ducks and got a solar panel and charge controller with the trailer we bought for parts. In the future we definitely want to add more panels.
C) “Shore power” – the term shore power refers to when a skoolie or RV is plugged into regular household electricity, like at an RV campground you can pay to plug in and use their electricity. This electricity is 120 volt power (unlike with solar power) so it can be used to power your appliances directly and/or with the right equipment charge the batteries.
Different wires can handle different amounts of amps. Big fat wires can handle lots of amps. Little skinny wires cannot. Wire sizes are indicated by “gauge.” The smaller the gauge the bigger the wire. For example, a 2 gauge wire is a BIG fat one while an 18 gauge wire is a little skinny one. 12 and 14 gauge wiring is what is typically used in most houses. This chart shows how gauges correspond to how many amps a wire can handle. When you plug in at an RV campground, you may have a lot of amps traveling along that wire into your bus so it can’t just be a regular extension cord, it needs to be a big fat one – a 30 or 50 amp RV extension cord, like this or this. Again, Michael and I got lucky and my dad gave us one of these so we have a way to plug in at campgrounds.
D) Generators – like shore power, generators produce 120 volt power so it can be used to power your appliances directly and/or with the right equipment charge the batteries. We got a little 1,000 watt portable generator from Home Depot. Portable generators usually run on gasoline, diesel, or propane. People will tell you all about how different types of fuel are better or worse. We had planned on getting a diesel generator because our bus runs on diesel so it made sense if we were going to have some extra fuel on board that it be the same fuel our engine uses. However, we ended getting a gasoline powered generator because, guess why – it was cheaper. The advantage of generators is that even if you’re in the middle of the desert nowhere near electricity you can recharge your batteries or run your appliances if you brought enough fuel to power your generator. Major disadvantages are that most generators are very loud, and that generators need to be placed outside while running because they produce dangerous fumes. We basically bought ours to have as a backup measure. We don’t really intend on using it on a regular basis. Maybe we should have just gotten more solar for the money…
E) Alternators – in your car the alternator is the part that charges your car batteries while the engine is running. In skoolies some people use a “charge splitter” to make it so the bus’s alternator is charging both the bus’s start up batteries and the batteries that power the lights and electrical appliances of the skoolie. This is pretty great if you’re planning on being on the road and running the engine often, but pretty useless when you’re planning on being parked the majority of the time. Since neither Michael or I are auto mechanics, we were WAY to chicken to try messing with this and risk screwing up the bus’s alternator. So, if you’re thinking of doing this, unfortunately you will have to check out another blog. Searching for info about “charge splitters” would be the first place I’d look.
Phew! So those are all the most common sources of power, and all the ones that I’m going to cover here. Now we can finally move on to the next section…
2) Inverters and Converters
When talking about different power sources I mentioned a couple times that some things use 12 volt electricity and some use 120 volt. But what if you have 12v and need 120v? Inverters and converters are how you change between the two. An inverter takes 12v and changes it into 120v. A converter does the opposite, changes 120v into 12v. A converter is useful when you want to use shore power (120v) to charge batteries (12v). An inverter is useful when you want to use power stored in the batteries (12v) to power household items (120v).
There are two basic types of inverters. Pure sine wave and modified sine wave. Pure sine wave is more expensive, but modified sine wave can sometimes not play nice with fine electronics like computers (I read some blogs saying it was fine and some blogs saying it could damage your electronics). Inverters also come in different sizes based on how many watts they can handle at one time. They will be labeled by two numbers, the lower number is the number of watts the inverter is happy with producing all the time. The larger “surge” number is the maximum number of watts the inverter can handle, but it can only do this briefly. You can use the spreadsheet with all the wattages of the things you use to determine how many things you’re likely to be using at one time and therefore how big of an inverter you need.
Michael and I were extremely lucky to get a Xantrex Pro Sine 2000 watt pure sine wave inverter from my dad. Have I mentioned how awesome he was helping us with electric stuff?
This inverter is extra great for a couple reasons. 1) It has places to connect input from shore power, input from batteries, and output to the rest of the skoolie electrical system. 2) it also has a built-in battery charger, allowing you to use shore power not just to run things on the bus but also to charge the batteries, so we don’t have to have a separate converter or battery charger unit like some skoolies do. 3) It has a battery temperature gauge and display panel that also you to monitor the conditions and charge of your batteries.
You know how when the power goes out in part of your house and you have to go down to the basement or wherever, use a flash light, reach inside a metal box, and flip some switches? Or if you’re me and you’re terrified of the dark (don’t judge) you make one of your other housemates go down and do it for you… Anyways, skoolies need a breaker or fuse box (Home Depot calls them “load centers”) too. Breakers and fuses protect your stuff. If too much electrical current goes traveling down the wires in your bus it can melt the wires, fry your outlets, and destroy whatever you plugged into the outlet. You don’t want this. Breakers and fuses are designed to “trip” when too much current passes through them and stop it from going anything further. The main difference between a breaker and a fuse is that once a fuse has been tripped it is dead and must be replaced. When a breaker is tripped it’s just like a switch that has been turned off, you can turn it back on.
You want to have a load center between your sources of power and your electrical outlets. If you have a fair number of things requiring 12v electricity as well as things requiring 120v, you will actually want to have two separate load centers for the two different systems. Since we only have two appliances that use 12v electricity (our refrigerator and our water pump) I wired those directly to the batteries (will explain further in the next section).
4) The 120 Volt System
A) Wiring – this is the wiring that goes from the load center to all the electrical outlets and light switches in the bus. I chose to have four different circuits: one for lights, one for outlets on the left side of the bus, one for outlets on the right side of the bus, and one for just the fridge. Each of these circuits has its own breaker inside the load center box. So, for example, if I try to plug in too many things on the right side of the bus, the breaker for that circuit will trip, turning off power to those outlets but won’t turn off the power to the left side, lights, or fridge.
I mentioned earlier how different thicknesses (gauges) of wire are able to handle different amount of electricity. The size of wire commonly used in houses is either 12 or 14 gauge. I chose to use 12 gauge for my wiring to have a little extra capacity (remember the lower the gauge number, the more current the wire can handle). The wire I used is called Romex and looks like this:
If you’ve ever wired a little circuit or looked at your car battery you may be familiar with two colors of wire – red wire that connects to the positive end of a battery and black wire that connects to the negative end of a battery. Romex has two wires that are sort of like this: a black wire (called the hot wire) and a white wire (called the neutral wire). In my opinion these names are stupid and confusing so I just call them black and white. What gives them their color is a protective coating over the wire itself. There is a third wire in the Romex has doesn’t have a protective insulation coating and so just appears copper. This is called the ground wire. The purpose of the ground wire is to redirect the electricity in the case of dangerously high current – its a safety measure. All three of these wires are enclosed together in yet another (yellow) protective coating and that is what Romex is.
You can get several different types of Romex. Romex is labeled as “a number”/”another number.” The first number refers to the gauge of the wire. The second number refers to how many insulated wires it has. So, the wire I used is 12/2 Romex. The outside color of the Romex indicates its size. 12 gauge Romex is yellow, while 14 gauge is white. Here is a picture of 14/3 Romex just for reference:
B) Outlets – So, we want to wire our 12/2 Romex to the outlets and light switches. Let’s start with outlets:
Your typical outlet may look like this. It will have 5 screws: 2 gold, 2 silver, and 1 green. The ground wire connects to the green screw. The white wire connects to the silver screws. And the black wire connects to the gold screws. To make these connections you need a few basic electrical tools:
- Wire Cutter (something big/strong enough to cut through the Romex)
- Box knife (or something else you can use to cut off the outer layer of Romex)
- Wire Stripper (like in this video)
- Needle-nose pliers
- Wire nuts (look like this)
Use the box knife to slit open the outside (yellow) sheathing. Remove the sheathing and brown paper inside. Use the wire strippers to strip away the white and black sheathing on just the ends of the wires (see above pictures). Then use the needle nose pliers to bend the ends of the wires into a nice hook shape (this takes a little practice). These hooks then fit around the base of the screws and then you can tighten down the screws with the screwdriver, securing the wire in place.
Home Depot has a good video (absolutely worth watching) showing this and an alternative called “quick wiring” where you just push straight wires into holes on the back of the outlet. Quick wiring is obviously much easier and less time consuming, but is also considered by many to be less reliable. There are two of the silver and gold screws so that you can have one Romex cable coming from the power source and one going to another outlet. Since there is only one green screw, you may need to use a wire nut to connect the two ground wires together with a third piece of wire that connects to the green screw. This is a great video on using wire nuts. Here is what the wiring diagram for one whole outlet circuit looks like:
Black = black wires
Red = white wires (white doesn’t exactly show against white background)
Green = ground wires
Orange = wire nuts
Yellow = Romex sheathing
Hope that diagram is useful and not too confusing… While we’re talking about outlets, I need to mention a special type of outlet called a “GFCI outlet.” You have probably seen this before, they have the little “reset” and “test” buttons in the middle.
These special outlets have added protection from shock. Like a fuse or a breaker, a GFCI outlet has the ability to “trip” and shut off the circuit if there is too much electricity. These are typically used anywhere that there is likely to be water such as in kitchens and bathrooms. Our bus has three of these (one in the bathroom and two in the kitchen). Wiring these is basically the same as with a regular outlet except that the wires coming from the power source (lines) must go to the bottom two screws, and the wires going to further outlets (loads) must go to the top two screws. Like this:
That’s it for outlets! Time to move on to lighting!
C) Light Switches and Lights
For your basic light switch you want a “Single-Pole Toggle Switch.” And when it comes to wiring, light switches are similar to outlets except they only have gold and green screws, no silver screws. The back of a light fixture will have one black, one red, and one green wire sticking out the back which you can connect to directly. The wiring for one switch and light looks like this:
Here is the diagram for how to wire multiple lights (don’t judge my horrible drawing abilities):
In a house each of your light switches and outlets need to go in a metal or plastic box that looks like this:
This box then gets mounted inside the wall with the wires coming out through a hole in the back of the box. However, in our skoolie the walls are too thin to be able to put boxes like this inside. So, we bought some pretty white boxes we could mount ON the walls instead of inside them. Face plates go on top of these and voila! Beautiful!
For light fixtures we knew we needed something cheap and also not very tall (since head room is already pretty limited in the bus). We found these lighting fixtures at Ikea for only $5 each. For the actual light bulbs we used LED bulbs (also found at Ikea) because they require so much less electricity than a regular bulb (ours are only 6 watts each). Here’s how they turned out!
So that’s the basics of how to wire your own lights, switches, and outlets. There are a lot of things you can choose and customize like switches, face plates, boxes, outlets, and where/how you hide your wires, but hopefully this section has given you a basic idea for how things go together.
5) 12 Volt System
12 Volt Appliances
Since I have only two appliances (fridge and water pump) that use 12v electricity and one solar panel that produces 12v, I chose to wire these items directly to the batteries and not have a separate 12v load center. The manual for the fridge listed a requirement of at least 18 gauge wire and the water pump manual required 14 gauge. I measured the existing wires coming from the solar panel and discovered they were 12 gauge, so I decided to use 12 gauge wire for all three to make it easy. Since a 12v system is much lower voltage, I just needed two wires (one red and one black) and didn’t need to have a ground wire The Romex wire used in the 120v system is “solid” wire. For the 12v system I used “stranded” wire which looks like this:
Stranded wire is actually the preferred wire for RV applications because it holds up better against the vibrations of a moving vehicle. Stranded wire also uses different type of connections than the screw terminals I explained earlier. This wire uses crimped connections, which actually are fun and easy to make, and feel very secure. To make this connections you need a crimping tool and some parts. The parts are color-coded by size. Red is for 18-22 gauge, blue for 16-20 gauge, and yellow for 12-14 gauge. Since my wire was 12 gauge all my parts were yellow. Here is a video on how to crimp, it’s SO easy, you just put the wire in a hole and press down the crimp tool. And here are some examples of tools and parts I used:
1 – crimp tool
2 – splice connectors
3 – spade terminal
4 – ring terminal
The “splice connectors” are used to instead of a wire nut to connect to pieces of wire together. The “spade” terminals pictured above are used to safely connect stranded wire to screw terminals like those we used above on outlets and light switches. You simply crimp the wire to the spade, then put the spade part underneath the screw, and tighten down. The “ring” terminals are used to connect the wires to the post terminals on the top of the batteries. Again the wire is crimped to the ring terminal, the ring is slipped on to the post terminal (those nubs that stick up on the top of a battery), and then a nut is tightened down on top of it. You can even stack multiple ring terminals on the same post. All of this stuff is fantastically easy and great! Yay for crimping! I wish 120v had been this much of a party.
Since none of these 12v items is going through a load center, they each need something that acts as a fuse or breaker to protect the system from too much current. For the solar panel, the charge controller fills this function. The charge controller also has a meter on it to allow you to check on the status of the batteries and how much solar power is flowing in to them.
Both the fridge and water pump manuals required the use of in-line fuses. The manuals specifically required that the fuses be on the red (positive wire). I used this cute little automotive fuses I found at Pep Boys. Here’s a very well done video explaining how to use them.
1 – fuses (color indicates amp rating)
2 – fuse holder
The wiring to the fridge and water pump also needed a way to be turned on and off. I actually used the exact same light switches as in the 120v system, I just used spade terminals to connect the stranded wire to them. I could have put a switch on the solar panel but I decided to be lazy and skip that since when am I really going to want to turn off the solar panel? I can always add a switch later, right? Here’s how the overall diagram of the wiring to the fridge (the wiring to the water pump looks exactly the same):
Connecting Batteries to Inverter
On the back of the inverter there are two big post terminals where you can connect the inverter to the batteries. Since the inverter is fancy and expensive (more expensive than anything Michael and I would have bought on our own), I made sure to read the manual THOROUGHLY. I actually even took notes. Yep, I took notes on the manual. It was long. Anyways, by reading the manual I found that the recommended wires for connecting the inverter to the batteries were 2 gauge wires. These are big fat wires and you’re not going to find them at Home Depot. I found them both on amazon.com and at AutoZone. AutoZone ended up having a better price for the length I needed so I bought them there. I bought one 2 gauge set to connect inverter to batteries and then a second 2 gauge set to connect the two batteries together.
A heads up when you’re shopping for these as they can have two different ends. One end is a ring terminal designed to slip on to a post terminal that has threads and a nut goes on top to secure it in place. The other type of end is designed to tighten onto a post terminal that does not have threads. Luckily, marine/deep cycle batteries usually have both threaded and non-threaded post terminals on top.
I’d read on many skoolie blogs that you want to have a master disconnect for your batteries and the inverter manual required the use of a fuse between the batteries and inverter. The type fuse mentioned in the manual is a fancy 300 amp fuse that requires a fancy fuse holder box… Hmmm, per usual fancy=expensive. Being the cost conscience cat that I am (*cough…cheap*), I opted instead to use a battery disconnect switch with a built in fuse. However, this built-in fuse says on the packaging that the fuse can handle “100 amps” but when you look at the actual fuse itself it clearly says that it is a 15 amp fuse… So who knows what that fuse is actually rated for. Most likely as soon as we try to power anything large with our electrical system, this fuse will trip and I will be forced to face the inevitable and go buy the 300 amp fuse and box like I should have done in the first place. But until that happens I will continue to use this little fuse. The master disconnect attaches to the negative wire and to the negative battery terminal. Here are some pictures:
Connecting Inverter to 120 Volt System
Okay, we have the batteries connected to each other and to the inverter. Now we need to connect the inverter to the load center and complete the wiring in the load center. Our inverter has a place where you can hardwire a connection but also outlets where you can plug into. For some reason I chose to use a Romex Plug instead of doing the hardwiring and directly connecting the wires to the inverter. In retrospect this seems silly and maybe later I’ll end up switching it to a hardwire design when I am feeling less lazy. Anyways, a Romex plug looks like this.
You attach the wires inside the plug and then just plug it into the inverter. Now we go inside the load center. It looks like this:
The first time I saw this, I went “what on earth is this weird swiggle nonsense?!?” I tried endless google searches trying to get some video or blog to explain how to wire up this thing. No luck. Once again my dad came to the rescue. I took this picture and had him send me a picture back with labels. And then I still didn’t understand so I made him explain it over the phone. Finally I got it. You remember how I mentioned (way back in this post back before you were tired of reading this crap) that some Romex cables have four wires (ground, white, black, and red)? Well see how in the load center there are two big flat metal plates? With two square metal boxes on them? And a third metal box attached to the row of little metal screws? Well, those boxes are where the wires from the power source go (from the inverter in our case). The white wire goes in the box attached to the row of screws. The red wire goes in one of the other boxes and the black wire goes in the other one. But wait! We don’t have a red wire! This system using both a black and red wire is only useful if you have a BIG circuit/appliance that requires 240 volt electricity like a clothes dryer. However, we don’t have any of that nonsense. So what you do instead is connect the black wire to one of these boxes and then connect the two boxes together. The ground wire should be connected to the actual frame of the bus. I have done this with a screw that goes through a hole in the back of the load center through to the metal wall.
So those were the wires coming from the inverter. How about the wires going to the circuits? The ground wires get grounded to the metal bus frame with a screw in the same way. The white wires go to the row of little screws (doesn’t matter which hole you put each one in). And the black wires connect to the breakers themselves under this screw:
The breakers then click and lock into the load center and you are ready to go! Woo hoo! OMG THE WIRING IS DONE!!!! THIS IS AWESOME!!!
Let’s test it. I’m not going to get my hopes up because nothing ever works on the first try, right? I’m just going to try to turn on a light switch.
I turn on the master disconnect switch.
I turn on the inverter.
I turn on the inverter display.
I enable the inverter on the display.
I flip the breaker to “on.”
I flip the light switch…
LIGHT!!! OMG THERE IS LIGHT!!! I AM POWERING A LIGHT SWITCH RIGHT NOW!!! OH. MY. GOD. Success is rare, glorious and golden. Finally getting the electricity working has so far been my happiest, most satisfying moment working on the bus. And after reading this post (or skimming it and at least seeing how long it is) maybe you can understand why.
Phew! You made it to the end of the post! Congratulations! You must have a very long attention span or be very desperate to learn electrical wiring. Either way you’ve made it and now you can go do your own skoolie wiring or eat a sandwich or take a nap or whatever. You’ve definitely earned it. 😀
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