July 29, 2018 Solar Power Installed on the 5th Wheel

We purchased a used 5th wheel to put into use as our winter home when we go south in the fall.  We prefer to "boon-dock" when we travel which means we camp out in the "wild" without electric, water and sewer hookups rather than use campgrounds that charge a nightly fee.

As a result we tend to modify our rigs to be pretty much self-sufficient.  They have water storage, propane for cooking, the furnace and for powering the refrigerator and water heater.  The generator is powered off the propane bottles and wired directly into the wiring system.  It has both 12 volt DC and 120 volt AC systems installed.

One of the most important changes we make is to install solar panels for charging the batteries (and we increased the number of batteries from one to three), which power the 12 volt DC system and also power an inverter to supply 120 volt AC current when we are not running the generator.

In this instance we installed two 160 watt solar panels on the roof of the RV.

One of the first things I do is take a photo of the specification plate on the back of the solar panel(s).  In this case both panels are identical units rated at 160 watts each (320 total).  This should supply far more power than we need even on cloudy days.

I purchased eight "Z" brackets to mount the panels to the roof.  Four for each panel.  You can use more if you desire but four has been adequate in the past and we've weathered some pretty strong winds.

The mounting holes from the factory are larger than needed and placed too far inboard for my tastes.  So, I move the edge of the bracket to the edge of the panel and mark where the new holes need to be drilled. 

NOTE: Do not make the holes so close to the inside edge that you cannot install the bolt that holds the bracket to the panel.

THIS IS VERY IMPORTANT: put some kind of stop spacer on the drill bit to keep it from going so deep that it contacts the solar panel surface.  When the drill bites through the aluminum frame it will bind and try to drive itself through and into the solar panel below.  Obviously you don't want that to happen!  I used a 1/4 inch drive deep socket as a drill stop.  They make special tools just for this purpose (I even have one!) but in my experience this works just as well and it's faster.

First bracket installed!  Seven more to go!

Once I have the brackets bolted to the panels I need to install them on top of the 5th wheel.  (Actually, you should have done some measuring first just to be sure that you have room.)  You want to have the panels clear of any tall objects like the AC unit and/or antennas.  Any amount of shade will decrease the charge rate on a solar panel.  Be sure that the panels can get the maximum amount of sunlight every day.

You can use strip caulk purchased at any hardware or auto parts store for the first layer of leak protection.  I had a vent installation kit with a roll of caulk left from a previous project and elected to use it.

Tear off a section about the size of the "foot" on the "Z" bracket then put it under the bracket.

Now drill hole down through the bracket and install a screw or lag bolt. When you torque it down it will squeeze out some of the caulk.  Trim the excess caulk away before the next step.

I used a caulking gun and sealer to thoroughly cover the bracket and bolt.  Be sure it seals tightly to both the roof and bracket.

One of the biggest challenges can be finding a way to get the solar panel wiring down to the charge controller and batteries.  In this instance I'm utilizing the holding tank vent.  This pipe goes down through the storage compartment which is also where the batteries are.

I ran the cables through the pipe then reinstalled the vent cap.  I'm using a MPPT charge controller so the panels are hooked up in series.  

If I was using a PWM controller I would have to hook the panel wiring up in a parallel circuit using another cable for splicing the two panels together.  The splices are available at any solar power supplier. 

For really big systems you may have to use both parallel and series wiring to get an acceptable combination of voltage and amperage.

The panels and wiring installed on the roof.

This is the vent line from the holding tank.  It's 1 1/2 inch PVC pipe.  I just cut a section out, ran the wires through and measured them, then ran them through the "T" and glued the "T" back into the vent pipe. There should not be anything except the odors from the tank in the line.  I drilled a couple of holes barely larger than the electric cable through the plug.  Ran the wires through the plug then glued it in place.

Next I used sealer to completely seal off the vent and wires.

Next I ran the wires from the batteries to the charge controller.  You want to hook the battery wires up first because many charge controllers sense the battery voltage then automatically select the 12 volt or 24 volt options from their programming.  It you hook the panels to the controller first it can get "confused" about whether your system's battery bank is 12 volt or 24 volt.  The input voltage from our solar panels is about 35 volts.  The charge controller reduces that down to around 13.5 volts (depending what charge "mode" the controller is using at the moment) to keep from overcharging the batteries.  A charge controller's only reason for existing is to properly charge and protect your batteries from over charging or being discharged too deeply (although other systems bear more responsibility for that).

Three batteries should be adequate for our needs. They are hooked together in a parallel circuit.

You can see the charge controller installed to the inside wall near the opposite side in this photo.  You need to leave plenty of clearance for air circulation around it.

You can see the back of the inverter on the left side.  The large black "box" is our inverter which changes the 12 volt DC current to 120 volt AC current.  This one is rated at 1,750 watts.