Idealistically, I had hoped to make a solar array capable of running an air-conditioner. The truck came with a sizable battery bank and inverter; however, air-conditioners use a A LOT of power. The usable area of the roof and the efficiency off panels that could be purchased in small quantities were the limiting factors in the system. In the end, it turned into cramming as many watts onto the roof as possible affordable. I haven’t quite determined how realistic it is to run an A/C off the final array yet, but I can run one for short bursts.

How it works/ Overview

The solar system consists of the array, controller, and battery bank. The solar array collects energy and is sized to keep the batteries charged. The controller uses this energy to keep the batteries charged and keeps the panels operating at peak efficiency. The batteries store energy to run the load and are sized based on the estimated energy needs. Ideally when designing a solar system you would do a power budget to determine how many watt/hours you will need from all of your loads. From this, you determine your battery and solar size based of how much sun you expect to have. For example: you expect to have to run two days without solar because its rainy.

In my case, I inherited a rather large battery bank in the truck and attempted to size the panels to keep it full and run as much load as possible.

Mounting

The mounting (called racking in the solar industry) is raised off the roof on supports. This serves two purposes:

Heat: Solar panels get very hot. The gap helps isolate the roof from this heat and allow air to circulate around the panels. (They generate less energy as they heat up) Mechanical support: The roof of my box is very flimsy fiberglass. The mounting carries the weight out to the beams at the top of the walls.

I had originally planned on fabricating a rack out of steel tubing for mounting the solar. However, after looking at the LEGO-like aluminum Ironridge XR1000 racking system at CED Greentech I went with this route. Also being aluminum reduces the amount of weight I had to add high above the CG and doesn’t create a galvanic corrosion risk with the aluminum box structure. The Ironridge system includes the XR1000 rails, “UFO” Panel clamping bolts, L-brackets, hardware, cable clips and end caps. They may have sold me something a bit overkill, but the rails can support me waling up there as needed.

End bracket, PVC pad, SS hardware Much fiddling with picking a spot to mount each rail

The end brackets are mounted through the roof to the structural member that runs along the top of the walls. The roof is held down with blind rivets through the top fiberglass. These rivets are spaced too close for the end brackets to sit flush with the roof. In order to secure the end brackets I had to drill out a rivet and use the hole for the stainless steel carriage bolt. The end bracket sits on a PVC rubber pad to help spread the load to the textured fiberglass. A stainless lock nut is used to keep the hardware from coming loose. The holes (and between the pad and bracket) were sealed with dicor self leveling sealant.

Test Fitting rails to end brackets Mounting the panels

There are three cross members per panel row (so 6 total) and the panels are spaced out to accommodate the fireplace chimney and the allowable span of the aluminum planking catwalk. The aluminum catwalk allows for maintenance access to the panels and serves as a conduit for the cabling. I made a ladder for accessing the catwalk which mounts between the lift-gate and back wall.

Array

The array consists of four LG 320W panels, and were sourced from my local CED Greentech branch for about ~$1 per/watt. I found this to be the cheapest option for buying a small number of high grade panels. Vendors prefer to sell solar panels by the pallet and shipping bulky panels is expensive.

Each panel has an open-circuit voltage of 41V and short-circuit current of 10A. To stay within the Voc parameters of the controller the panels are arranged in two parallel circuits of two panels in series. The series strings consists of the two panels on either the passenger or driver side. The panels have 3ft pigtails with the MC4 style connectors. (there appears to be two styles of solar interconnects, so keep this in mind when ordering cables) that are gendered to plug positive to negative. I had to use extension cables for the wire runs into the truck.

The cabling is secured to the rails using ironridge clips and then is run along the passenger side aluminum planking to the cable glands and down into the solar breaker box.

Cutting holes for cabling Finished cable glands Conduit for driver-side cabling Cabling running along rails to planking Finished installation

On the driver side a piece of non metallic conduit was used with some custom aluminum brackets to secure the cable connection between the driver side panels.

Battery

The truck came with six 6V batteries in a 2 series-3 parallel arrangement. The batteries are mounted in a drawer under the chassis. Unfortunately, the batteries were toast and

needed to be replaced. This arrangement of batteries is common in golf carts. I was able to find a local-ish golf cart shop advertising a good deal for US Battery batteries on craigslist. He also offered to make nice #4 jumper cables for a nominal fee.

The new US Battery 2200 XC2 batteries have a 232 A/hr capacity. This places the total battery bank capacity around 8.3kW/hr, however, a full discharge will wear out the batteries. Ideally the batteries would only be discharged 50% to maximize the life.

After installing the batteries into the drawer I discovered that the terminals on the new batteries sit about 1/4 inch higher than the old and had a lovely tendency to short to the chassis when attempting to close the drawer. I ended up having to cut out the drawer and weld in some modifications to add about an inch of height.

OUCH! kinda bodgy…extension to battery drawer Roger being too helpful

The series and parallel connections are made between the batteries with #4 jumpers. The center set of batteries are connected to the 4/0 cables that connect the battery bank to the inverter. Also tucked in between the batteries is the temperature sensor (blue wire) used by the controller to adjust the charging current.

Controller and Wiring

As previously stated, the solar array is connected in two parallel circuits of two panels connected in series. Each circuit has an independent 15A breaker. The combined solar array circuits are protected with a 115V surge protector for lightning protection.

This combined circuit is then tied to the Midnite Classic 150 Maximum Power Point Tracking (MPPT) controller.

The solar panel’s most efficient voltage/current condition changes as the sunlight changes. The controller adjusts the load on the panels to keep the efficiency as high as possible.

Additionally, charging the lead acid batteries requires a charging profile/program to be followed so they are not damaged. The controller also manages the charging of the batteries and provides a state of charge estimate. The charging is adjusted for the temperature of the batteries and any loads that may also be drawing power while power is available.

The 12V output of the controller is protected with a 100A breaker and connects to the batteries through #4 gauge cables.

I purchased most of the electrical components from Northern Arizona Wind & Sun as they had best pricing and all of the components. Side note: Midnite Solar has weird product names…

Wiring up the Solar Lots of stuff! Finished!

The solar circuits come in from the roof grommets and directly down into the electrical cabinet above the fridge. This cabinet contains the combiner breaker box and and controller.

The combiner box consists of:

Big Baby combiner box

Two 15A 150V DC DIN rail breakers

MNSPD 115V Surge Suppressor

Breaker Bus Bar

Short Terminal Bus Bar