Installing solar panels, CTEK D250S charge controller and Xantrex LinkLite on a Sprinter camper van conversion

Posted on Tuesday, Aug. 09, 2016 in Van Building

When I first built out my Sprinter camper conversion, my power requirements were not very high. As I wrote about in my previous post about the electrical setup, my only power consumers at the time were my roof vent fan, LED lights and the occasional charging of my gadgets.

During the first year I used my van, I got by with using a simple cooler for my food and drinks. This worked out really well, but it was tiresome to track down blocks of ice every few days in new towns. It was also annoying having to deal with soggy food from all the melting water.

For my second three month summer trip in the van, I decided to make the jump and install solar panels and purchase a fridge. Thanks to having planned ahead in my original electrical build, I did not have to do too much rewiring nor upgrade my house battery for extra capacity.

Materials list

The Plan

The only major additional power consumer I was planning for was a 12V fridge. I’d done my research on ARB, Engel, Webasto and others, but had not made a decision on which I’d buy nor where I’d fit it in my build. Given my fridge options, I knew that I could expect an additional power draw of no more than 5amps for a roughly 20% duty cycle. This means I’d expect to consume about 25 amp hours in a 24 hour period at the very worst. But really, I’d only need to be concerned about having enough battery capacity for the nighttime hours and the occasional thick overcast days. The other times I should plan to have enough surplus power from my panels to charge my battery and run my fridge.

This left me with the question of which and how many solar panels I ought to install. From the beginning, I had a hunch I would go with 2x 100W panels. Figuring out the actual expected output of any panel was proving difficult for me, so I decided I would just overbuild to ensure I could keep my battery topped off with any amount of usage I threw at my battery, even if I was waiting out a rain storm with dark skies for days.

I shopped around for solar panels a bit, but the most popular and easiest to purchase I found were the 100W Renogy panels available on Amazon. I purchased two of these panels, a couple Y-adapters to run the panels in parallel, MC4 cable, MC4 connector tools, a cable entry and some 3M VHB tape.

Attaching the panels

Mounting the solar panels to the roof seems to be a touchy subject among the van-building community. Some suggest just using VHB tape, others say screws/rivets are the only option. I wanted to use the VHB tape option as this meant less drilling and fewer leak points in my roof. However, I knew that often the weakest part of using VHB tape is the potential that it will just peel the paint off the roof. And older Sprinter vans are notorious for having terrible paint jobs.

But I decided to go that route anyways, again, with some overkill to ensure those babies stuck to the roof. I’d seen that AM Solar out of Oregon sells a kit to mount panels using only four small feet per panel, these feet being affixed to the roof using just a bit of VHB tape.

If they can get by with that little bit of tape, I ought to be okay to using enough tape to run the entire length of my panels!

To mount the panels to the roof, I decided to keep it simple by using two run of 1 1/2” aluminum L-channel down the sides of the roof, then to rivet the panels on to that. Some people mount their panels to they’re tiltable so that they can raise them to face the sun when it’s low in the sky, or to be able to clean under the panels. But I figured since I rarely stay in one place for more than a nice, I’d never bother tilting my panels. And cleaning under them seemed unnecessary. If I really needed to clean under them, I’d just drill out the rivets and remount them once clean.

The mounting process was pretty straight forward. I made the decision to mount the panels perpendicular to the van as this would bring the panels closer to the edges of the van and save roof space for possible future expansion. This also meant I would not need a mounting fixture running down the center of the van, only on the edges.

One thing to note here is that the top of the van has a slight curve from side to side. As you’ll see in the photo below, I had to rivet the panels at the very top edge of my L-channel in order to span the curve. If I were to repeat, I might try to use some slightly taller L-channel to give myself extra room.

To get everything measured out, I hoisted the panels on to the roof and carefully moved them into place just in front of my roof vent leaving room for the vent lid to open. I also left maybe a half an inch or so between panels for air flow. Square everything up and place the pieces of L-channel along the edges. Double and triple check everything, then mark it all with a pencil on the van roof.

Solar panel alignment
Solar panel alignment
Solar panel alignment
Solar panel alignment

If you’re confident in your measurements, take everything back off the roof and begin prepping for the VHB tape with cleaner, alcohol and VHB adhesive promoter. Make sure you don’t erase your pencil marks in the cleaning process!

Once the roof is clean, give the tape surface of the L-channel a cleaning. Once all is clean, apply the VHB tape to the L-channel and press on well to eliminate any bubbles. Then hop back up on the roof with your L-channel pieces and carefully line them up with your pencil marks and stick them into place.

Note: This VHB tape stuff is sticky! Once you stick it down, there is no going back without substantial work. Make absolutely sure you’ve got it lined up before sticking it into place!

Once the L-channel pieces are stuck down, you’ll want to apply a big bead of self leveling lap sealant around the perimeter of each L-channel. This will ensure that rain and ice don’t get under the bracket and penetrate the VHB tape.

Now, hoist the panels back up and slide them into place. connect the panels together with the Y-adapters and run the cables up in the direction you’ll want them to go through the roof hole. Then use some shims to lift the ends of each panel up enough to clear the curve of the roof. Once happy with each panel’s placement, mark out a few spots along the edges for your rivet holes. I use three rivets on the end of each panel, though two would probably be fine. Have a friend help you hold the panels into place while you drill out the rivet holes. I did one at a time. Drill, install rivet, drill, install rivet. This ensured that everything stayed lined up between drillings.

Solar panel bracket
Solar panel bracket

Running the wires

Now it’s time for the scary part, to actually drill a hole in the roof. After looking at a few options for cable entry, I decided on Linksolar cable entry with dual entry ports.

When selecting the location for my entry, I wanted as far forward as possible for a couple reasons: 1) it meant my wires would drop in over the passenger seat and I could run them down the seat belt column into my electrical box easily and 2) it left a lot of wide open space on the roof for additional panels if I ever decided to expand.

I crawled back up on the roof and found a spot that avoided all the roof support ribs, squared up the cable entry where I wanted it and traced the outline. I then took a 1 1/2” hole saw and cut a hole in the roof. Then just as I talked about in the roof vent installation, clean up the cut edge and apply some primer to prevent rusting.

To cover the sharp edge, I found a plastic grommet laying around the shop that I hacked into something usable with a knife. It slipped down into the hole and I glued it into place. This would keep the rough edge from cutting into my cables.

As for the cable, I purchased a single 50 foot stretch of solar cable with MC4 connectors on the ends, one male and one female. I cut this in half as I didn’t need more than about 15 feet to get from my panels down to my charge controller. I ran the cables through the cable entry before installing it, then finish running the cables through the hole and into the van. It’s much easier to fish the cables through when you can actually see the hole. Once the cables are in place, clean up the roof surface and prep for more VHB tape just as before. Once clean, put some tape around the perimeter of the cable entry, stick it down and apply lap sealant.

Cable entry
Cable entry

Now we’ve got everything ready for the charge controller installation inside!

Charge controller

Awhile back, maybe six months ago I got distracted researching charge controllers. I stumbled upon one on Amazon that I had never heard anyone mention before, the CTEK D250S. It’s a unit that acts as both a MPPT solar charge controller and a battery isolator that will draw excess power from the alternator. It even handles the 5-step charge profile for AGM batteries. The limited reviews on Amazon were very positive, too. I had setup a price watch and before long a used one popped up for $100 less than retail. I bought it and set it on a shelf awaiting the day I installed solar panels.

Now was the time to pull this unit out of the box. Setup was a breeze. I pulled my passenger seat off the seat box and tore apart my electronics. The battery and fuse block would remain, but the WirthCo 125 amp Battery Isolator would go.

Remove seat
Remove seat

I did just as I had done with my first round of electrical buildout, line everything up so wires could all be run between components and screw everything down.

Wiring the components was a piece of cake, the hardest part being measuring the cables out perfectly and crimping on the ring terminals.

In the photo below, you’ll notice a couple additional components in the lower left: those are the shim and fuses used by my Xantrex LinkLite power monitor. Just ignore those for now, we’ll talk about those in a bit. The brass bar is a ground bar added to make it easier to ground everything together. It’s not critical, but makes wiring a lot easier.

Note: before you starting wiring in your panels, it’s a good idea to cover them up so that they are not putting out any current while you’re working with the bare wires. I used a very thick blanket.

Here’s an outline of the wiring (sorry I haven’t drawn up a diagram, but you can get an idea by the photo below):

  1. Run the cables coming from the starting battery into the + and - terminals of the CTEK unit. It’s a good idea to remove the 100 fuse up under the hood while you’re rewiring things. You’ll reinstall it after you’re done with the wiring. The red cable goes into the terminal labeled with a little alternator image, the black cable goes to the ground terminal (or ground bar).
  2. Run the cables coming from the solar panels in a similar fashion. The + cable (unfortunately, it’s black instead of red) will go into the CTEK’s terminal labeled with a solar panel, the - cable goes to the ground terminal (or ground bar).
  3. Run a small piece of cable between the + out from the CTEK to the + post of the house battery.
  4. Run a small piece of cable from the - post of the house battery to the ground shim (or in my case, through the Xantrex shim, then into the ground post).
  5. Run a small piece of cable from the + post of the house battery to the fuse block.
  6. Tape the thermometer from the CTEK unit near the + post of the house battery. This helps it charge efficiently as the battery warms and cools through the charging cycles.
Battery box
Battery box

Once you’re happy with the wiring and have triple checked everything, pull the cover off the solar panels and watch all the lights on the CTEK fire up!

Now, on to the power monitor.

Power monitor

Just as I had with the CTEK unit, I had found the Xantrex LinkLite on Amazon and it didn’t seem like many people in the van building world were using it, but it seemed perfect for my needs, just a little expensive. A quick check around the internet and I found one on eBay going for $100, less than half the retail price!

This unit is, oddly enough, sold without the cables to hook it up – those are an additional $100. I decided to roll my own with some ethernet cable I had laying around and some simple fuses from Fry’s.

The instructions for wiring up the monitor are included with the device, so I’ll spare you the step by step instructions. You can see generally how I setup the shim and the fuses in the above photo.

I ran the ethernet cable from my battery box up into my kitchen cabinet where I chose to mount the monitor for easy reading. There’s not much to detail for you here, it was a simple matter of fusing all the live wires so that a short did not fry my Xantrex and then some simple wood working to add a place to mount the unit. You should be able to get the basic idea from the photos.

Note: I also added a USB charging plug next to my Xantrex, you can see that in the photos as well.

Monitor out
Monitor out
Monitor in
Monitor in


That sums up how I got the solar panels installed and wired up. I hope this gives you some idea of how to get solar panels installed. Of course, your install will likely be a bit different than mine as you choose the components to fit your needs.

Until next time!