Underneath Cara’s bed is the wiring panel where the battery is connected to the rest of the DC wiring. This is a prime location for the solar charge controller because of it’s proximity to the batteries. Later, I’ll install the inverter nearby for the same proximal reason. The existing wiring in this location was a positive bus bar, a negative bus bar, the ‘store’ mode disconnect relay, and a positive DC breakout box.
Also found in this location was the ends of the solar pre-wire placed by Airstream. I knew they were there, but the wire gauge was so small that I had to replace it anyway.
As I was adding plenty of components, I had to do a little rearranging of the existing components. They were just screwed into the plywood panel, and I was able to re-arrange them without too much difficulty.
In principle, the solar panels are wired to the solar charge controller, and the solar charge controller is wired to the positive and negative bus bars. In practice, there are a few additional details.
The first component I installed was the isolator switch on the positive wire leading from the solar panels. By switching this off, I was able to protect myself (and the equipment) from an accidental short during the rest of my wiring project. (A ‘short’ is when you accidentally connect two wires that are not meant to be connected. Ever accidentally touch the clamps of a jump start cable together? That is a short.) After installing the isolator switch, I left it off for the rest of my install.
I next wired up the solar charge controller. A short run from the just installed isolator switch on the positive side, and the negative side of the cable from the rooftop panels. The next step involved connecting the ‘out’ side of the controller to the existing DC system. The positive side of this connection is run through a switchable 30 amp DC breaker. This switch automatically flips off if the solar charge controller attempts to output more than 30 amps. With a maximum output of approximately 24 amps, I suspect this will never trip. It DOES serve as additional protection, and also as an extra isolator switch should I manually switch it off. The positive side is then wired to the positive bus bar.
The negative side of the charge controller ‘out’ connection can be wired directly to the DC bus bar, but I cheated slightly and attached it to our last new component: The battery monitoring shunt. This magical component can measure the flow of electricity from one side to the other. This enables both a real-time view of charge/drain activity on the battery, as well as keeping track of how many ‘amps’ or amp-hours are left in your battery. This measure is unaffected by load (like voltage) and gives a great indicator of battery charge state at a glance.
The monitoring shunt is installed between the negative terminal of the battery and the rest of the negative half of the DC system. I moved the negative battery cable from the DC bus bar and connected it to one side of the shunt, and added a new cable between the other side and the DC bus bar. Now, every use of DC power can be monitored. More on that later.
I connected the negative side of the charge controller DC ‘out’ to the shunt as well, on the non-battery side. (ONLY the battery should be connected on that side of the shunt. EVERYTHING else is connected on the other side.)
At this point, everything ‘major’ is in place. In part 3 of this series, I mentioned running remote cables from the kitchen cabinet down to the electrical panel and along the same run as the solar wire. At this point, I attached these remote wires to their various components. The IPN Pro Remote cable attached to the solar charge controller. The shunt monitoring cable attached to the shunt with little screw mounts.
The last step I’ll describe was really the hardest step of this last phase. The solar charge controller has a remote temperature sensor that allows it to adjust it’s charging based on the temperature of the battery. This cable attaches to a battery terminal in the battery box, and to the solar charge controller inside the Airstream. The existing battery cables are run through a heavily caulked hole in the floor. By poking carefully with a phillips screwdriver, I was able to poke a hole through the middle of the bundle without damaging any existing wire. After attaching it to the battery and threading it out of the battery box, I ran it alongside the battery wires, and protected it with some plastic wire wrap. I shoved it through the hole I poked, and then squooze a bunch of silicon sealant around the wire from the top and the bottom. The sensor attached easily to the charge controller, and then I attached the cover.
At this point, everything was installed. I only needed a short length of wire and a few wire terminals from the store, and everything else was provided in the installation kit from AM Solar. Between their instructions and the inspection of Dave Zimmerman’s wiring, I was able to work out all the details and complete the self install.
The only thing left to do was to flip the system on. I started with the solar isolator switch, but nothing lit up upon flipping that on. Next was the 30 Amp breaker, and that did the trick. Things started blinking, the power in the Airstream worked again, and I immediately started my addictive ‘check the solar monitor’ habit.
Really, I’m surprised that everything worked out as well as it did. I re-attached the plywood panel that covers the wiring, and the project was complete. Really, I had a few random things to do, like zip-tie wires in various places, but it all feels better when the darn thing works!