Installing My Van’s Solar Panels
While we were cutting holes, it was time to start the solar.
Solar was a journey in itself. We might have done more research on solar than any other part of the build. It was important to get the wires run before doing any interior woodwork. We are very happy with what we ended up with and so far would do it again the same way with just one modification (which we just did).
We went with 400 watts of solar panels (4 panels of 100 watts each). They key here is to get energy efficient solar panels and ones that will withstand the elements of driving. We chose Renogy panels as they seemed to fit our needs the best. When wiring panels you need to decide on parallel or series. That is the one thing we just changed…more on that in a minute.
As discussed in the Electrical blog, solar panels connect to a controller. We chose what is called an MPPT controller. Technically that is a Maximum Power Point Tracker, but what it stands for does not help with your build. What does help is use a MPPT controller if at all possible. The purpose of the controller is to take the voltage and amperage from the solar panel and convert it to the amount that charges your batteries the fastest and safest. MPPT does this. When selecting a controller you need to be considerate of the voltage and amperage coming in.
My solar panels have roughly 20 volts for each panel and approximately 8 amps. Here is where we get a bit technical, but I will keep it to the basics but with enough info so you can decide what you want to do. You can hook your panels up in series or parallel.
Series: If you have two panels, both will have a positive and negative wire. In series, you hook the negative of panel 1 to the positive of panel 2. In doing this you double the voltage and keep the amperage the same.
Parallel: In this situation you connect your positives together and your negatives together. You double your amperage and keep your voltage the same.
Why do you care?
If there is a shadow on a solar panel, it shuts down that panel. If you wire your panel in series it will shut them all down. If you wire them in parallel, it only shuts down the one with the shadow. There is a lot of electrical engineering science going on behind the scenes, but know that one of the two big differences is the impact of a shadow.
The other big difference is the volts coming into the solar controller. Some controllers (like Victron) require 5 volts more than the batteries to start charging them. This means if you are running 12 volt house batteries, the voltage going into the controller must be 17 volts to turn on the charging part of the controller. As I said above, my panels (and most of them) have a voltage of 20 volts, so that is no issue. 20 is more than 17 to that is enough for the charger. BUT, there are times in the day where you will not get a full 20 volts. Early and late in the day are examples of this. So you can overcome this by going in series.
In series, the voltage is doubled (again there is electrical engineering science behind this) and you would get 40 volts coming into the controller which is way more than needed so you get longer charging days. If you have 4 panels like me, you would be getting 80 volts.
So what to do?
You want enough so that your controller starts to charge the house batteries. But you also want to be thinking of in series if one panel shuts down all of those in series shut down. I did the best of both worlds. I connected two of my panels in series, the other two in series, and then connected the two pair together in parallel.
But earlier I said there are two things to consider when connecting your solar panels. The shut down impact is one, the other is not overloading your controller.
My controller is a 100 volt 40 amp controller. That means it can take in up to 100 volts and up to 40 amps and be happy. Remember, your controller is a magician and takes the volts and amps it gets and converts it into the right amount to maximize the charge to your battery. You do not want to exceed its ratings though. In my example, if I put all of my panels in series I would be getting 80 volts and the amps would still be 6. If I did them all in parallel, I would have 20 volts and 24 amps. Remember, when put in series the volts add together and the amps for the panels stay constant and in parallel it is the amps add together and the volts stay constant.
If my panel is rated to 100 volts, then 80 going in is safe for it…right? Technically yes. I will not get into the deep electrical engineering here, but temperature impacts how many volts the panel produces. Make sure the controller you use can support the solar configuration you want to have. You can find a solution, just be smart about it.
One more item…
You will need to get the wires from the solar panels (outside the van) to the controller (inside the van). Cut a hole in the van top in a strategic location. Strategic location is one that is easy to get the various wires to and is out of the way. I put mine under a solar panel. After you cut the hole (I cut about a 1 inch hole) paint the edges to prevent rust. Then add a rubber grommet to help protect the wires from rubbing on the sides of the hole. Finally put what is called a gland over the hole and put the wires through the gland. Seal the gland using lapping compound.
Grommets for my two holes
Gland as I was getting it to set before the lapping compound. The weights came off…they were there to help it sit flush with the van.
Key points to this blog are:
If you connect your panels in series, add the voltage from each panel and that is what will go into your controller. The amperage will not change. If each panel is 6 amps, in series they will still be 6 amps.
If you connect your panels in parallel, add the amperage from each panel and that is what will go int your controller. The voltage will not change.
Your controller might require 5 volts over your house batteries to charge. Make sure your panels are putting out that many volts.
Calculate how many volts and amps you will be producing and choose a controller that will handle that configuration…or choose a controller you like and configure your panels so they do not overload it.
In parallel, if one panel fails (e.g. shadow), the rest will be okay. In series, one failing will fail all of them. It breaks the circuit.
Make sure you protect the wires coming into the van from the solar panels. Use a gland to protect from the elements.
Below are links to products we used. I feel like we have kept Amazon in business. Almost all our materials came from there. I am happy to share the fruits of our research to save you some time. And we did a lot of research. As a disclaimer, I am an Amazon Associate. This means that I may earn a small commission for purchases made through these links. There is no extra cost for you.