When I started researching what I’d need to make the bus reliably solar-powered for everything I’d need, it felt like I was reading a different language. Watts, voltage, amps, amp-hours, fuses, 8 gauge wire… the list goes on. It was foreign. To be honest, it still feels unfamiliar, but I know enough now to diagnose basic issues when they happen.
The first thing that I learned when researching, is that every solar setup is different. This makes it INCREDIBLY difficult to figure out the very basics of what you need. My goal with this blog post is to lay it all out in the simplest terms so that it makes sense, and you’ll be able to understand it enough to run with it for your own build.
Disclosure: This post contains Amazon.ca affiliate links, which means that if you click a product link and buy anything from Amazon.ca, I will receive a small commission fee. The price you pay remains the same, affiliate link or not. I never recommend or link products that I don’t believe in. I only include the links that I would actually recommend!
All About Electrical!
Learning the basics
The first thing you need to know for your skoolie’s electrical system is that there are usually 2 kinds of power that work together in your typical bus build.
The first one is AC, otherwise known as 120V, 120 volt, or “household” power. This is the kind of power that you would use in your regular home to plug in your coffee maker, vacuum, etc. Think of the standard household outlet. This kind of power requires an appliance called an Inverter to work in your solar setup. We’ll go into this more later.
The other one is DC, otherwise known as 12V, or 12 volt. This kind of power is for smaller appliances like lights or phone chargers. Think of your typical USB plug. This kind of power can run straight off your battery – we’ll go into this more later too.
There are more types of power you can have, but these are the basic ones that have worked for us in the bus. Both a 12v and a 120v system can be powered by solar panels in your bus.
Now that we know the 2 kinds of power available to you, here is your first decision:
Will you need to plug in bigger appliances, like a coffee maker, to an outlet? Or, will you be okay with just charging your phone and some basic lighting?
In our build, we wanted to have at least 2 outlets so that if we needed to plug in anything bigger, we could. The rest of our system runs strictly off of 12V (or DC) power.
Let’s start with the big picture... Skoolie Conversion Electrical Diagram
The diagram below is a very basic depiction of how it all comes together. Once I understood how all the pieces work, I was able to learn more about the details of my own build, and what I would need to buy.
All About 12V!
Sizing your battery
When working on the electrical part of your build, it’s a good idea to think about what kinds of things you’ll need electricity for, first. It’s easiest to work backwards like this, so that you’ll know how much power you’ll need, and therefore how big your battery needs to be.
Batteries are sold with an “amp-hour” rating. An amp-hour tells you how much amperage a battery can provide for exactly one hour.
To figure out what kind of amp-hour rating you need for your battery (or how “big” it needs to be), I started out by calculating how many hours I’d use each electrical item for each day. Then, I figured out what that equates to in amp-hours to find out how many amp-hours I’d need from my battery.
So, what kinds of things will you need electricity for?
1. List all electrical items you’ll need
I started by making a list of all the things I’d need electricity for… including the small things I’d use daily, like coffee grinder and laptop chargers.
Bedroom lights – highly recommend this dimmable 2 pack that comes with a USB phone charger!
2. List the wattage of each of those appliances/devices.
This can usually be found on the power cord from the device, on the item description from wherever you ordered it from, or in the manual for the device.
If you can only find the amperage, you can use the equation below to find the wattage.
Wattage = Voltage x Amps
3. Now, add the number of hours you plan on using each device.
If you only plan on using the appliance or device for a few minutes per day, make the number a product of an hour. For example, 30 minutes would be 0.5 hours.
Another thing to note about different appliances is the “working time”. Our mini fridge is really only “working” for about 8 hours out of the day to remain at the correct fridge temperature. This is why we only accounted for 8 hours of working time for the fridge, even though it might be plugged in all day.
4. Get the total watt hours per day.
Multiply the numbers together!
Wattage x hours = watt hours
5. Get the total amp hours per day.
Divide each number by 12.
Amps = Wattage/Voltage
In a 12v system, the voltage is 12.
Therefore amps = wattage/12.
6. Add it all up!
You can see in the example linked here and screenshotted below, our system uses just over 128 amp-hours per day.
Our battery is rated for 300 amp-hours. This means that, in theory, we can go just over 2 days with absolutely no sun before our battery dies. (Since 128 x 2 = 256, that means we can go just over 2 days before we exceed 300 amp-hours).
It’s a good idea here to account for more than what you expect to use, in case you find yourself in a cloudy spot for a few days. You’ll also want to consider the weather that you’re planning to be in to make sure that you can last more than a few days if you need to.
I purchased this 300 amp-hour battery from CanBat and it has been great. There are a ton of different batteries you can buy depending on your power consumption and budget.
And now… Solar panels
The thing to consider with solar panels is – how fast do you want your battery to charge? The more solar panels you have (or the more watts of solar power you can collect), the faster your battery will charge.
I have 4, 100 watt panels mounted to the roof of the bus. I have found that this charges my 300 amp-hour battery pretty quickly (a few hours of full sun).
I purchased this Renogy Solar Kit that includes everything you need to install and mount your solar panels, and connect them to your battery. There are a few other things you’ll need to make the system work though. If you purchase this kit (or a similar one), Renogy even lets you choose what kind of solar panels you want based on weight and efficiency.
In between your battery and your solar panels is a device called a charge controller. It monitors and regulates the solar power coming from your panels to make sure that the battery operates in a safe zone.
The charge controller I have comes with a Bluetooth module so that you can connect it to your phone and see how much power you get, plus monitor your battery condition.
My charge controller was also included in the Renogy Solar Kit.
The only thing that the Renogy Solar Kit does NOT include which was CRITICAL for safety, is ferrules. These are little shrink wrap pieces of metal that slide overtop of the wires connecting the solar panels and battery wires to the charge controller. If your solar system doesn’t have strong and efficient connections, it can cause the connections to get extremely hot. When we wired the bus, I had no clue that bad connections = HEAT. Our bad connections ended up overheating several times before I noticed, and melted the plastic of the charge controller. This happens especially in a bus when things are bouncing around all the time! I added the ferrules as soon as possible to avoid any further damage and they have done their job perfectly! I haven’t noticed any additional heat after I added the ferrules.
Before, after (much better!) and my melted charge controller!
These crimpers were also handy for installing the ferrules.
Checking in... still with me?
Now you’ll know (generally) how to connect your solar panels to your charge controller, to your battery. With this information, you should be able to charge your battery! Now, onto the 2nd half of the project. This next part of this blog post talks about everything after the battery (like lights and stuff).
Here is where you’ll need to visit your local hardware store to pick up some 16 AWG wire in order to connect your 12V devices to the system. I started with purchasing this switch panel from Amazon. PS – big fan of this switch panel. It has 2 USB plugs and a car charger port so that you can charge phones and stuff right from the switch panel.
From there, we wired a battery disconnect switch to allow the switch panel (and associated devices like lights) to be disconnected from the battery. This essentially cuts off anything that uses energy from the battery. This is helpful if you want to diagnose a battery issue, or if you’re storing your bus for a certain amount of time and don’t want to drain the battery.
Next, you can wire in your devices like lights to the switch panel. We have bathroom lights, booth lights, bedroom lights, solenoid, water pump and 12v fridge switch wired to our switch panel. The reason why we decided to go with a switch panel is so that each of our devices (lights, water pump, solenoid, etc), have an individual switch that can be turned on and off.
All About 120V!
Sizing your inverter
I purchased this inverter from Renogy. We then wired it to 2 outlets – one in the kitchen and one by the booth.
To begin calculating how big the inverter should be, we started by determining the maximum power that we’ll need at any given time. Start by listing all the things you could be running at the same time from the inverter and the wattage that they use:
Laptop charger = 90 watts
Toaster = 1200 watts
You can google the wattage, or you can usually find it in the device manual or even on the power cord.
When we add these up, it equals 1290 watts. So, we needed to make sure that the wattage of the Inverter exceeds this. That’s why we went with a 2000W inverter! If you are careful about what appliances you use at the same time, you can get away with purchasing a smaller inverter.
Other things to note about inverters
When your inverter is running, it can get quite hot especially if you’re in a warm climate. Make sure to put your inverter somewhere that has at least 6 inches of airflow around it. We put mine in one of our booth bench storage boxes and cut out a little vent for airflow.
Inverters consume energy in order to convert 12V to 120V power. This means they’re not really that efficient, and you’ll lose power just by having your Inverter running. Our inverter has a power button so we make sure to turn it off when we’re not using it. We actually mounted Renogy’s inverter switch near our switch panel so that we can easily turn it off and on!
120V is like your normal household power. We got receptacles similar to these and wired 2 of them – one by the kitchen and one under our table. These are wired from the inverter to a fuse, and then to the outlets.
The only other thing that is wired to the inverter is our shore power plug.
Connecting to shore power
The other option you have when it comes to your inverter, is whether or not to wire it to be able to charge your battery via shore power. Shore power is the electricity you can get when you go to a campsite. It is also known as 30 amp power.
I didn’t think we would use this as much as we have! It has been a life saver a few times when there has been a week or so of rainy and gray weather and our battery starts to drain.
For that, you’ll need to wire a shore power plug like this one to your inverter. You’ll also need a 30 amp cord and that is what goes from your shore power plug, to the plug at a campground.
We also found this adapter to be useful whenever we found ourselves in a place that only had 15 amp outlets, like parked in someone’s driveway.
- Don’t rely solely on one blog post for your electrical build!
This is an interesting one since I’m literally telling you this in a blog post. But, when I started planning my electrical system I relied heavily on other people’s diagrams and ideas. I didn’t really take into account the reasons *why* they did what they did. It wasn’t until I got a better understanding of working with wiring and batteries and solar panels and associated equipment that I understood their reasoning. And consequently, I decided to alter my plan to better fit my own goals for the system.
2. Learn as much as you can!
If you’re lucky enough (like me!) to have a family member or friend who is willing to work on your build for you, learn as much as you can! Ask all the questions, record videos and take notes! You’re going to need this later on when something in the system fails or you have to diagnose a problem.
3. When in doubt, hire someone.
People do stuff like this for a living and there are a ton of resources available online, paid and free. If you come across a problem that will either be too challenging or time consuming for you to do, don’t be afraid to hire someone to get it done safely.
Putting together your plans for your skoolie or van? Check out my propane diagram and step by step guide for getting that all sorted!
If you’re still here, thanks for sticking with it! I’m always available to answer questions as well.