My solar system for the Roadtrek has changed. I first installed a solar charger and portable panel in 2014. This was for the AGM lead acid batteries.
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| 200W Panel on Roof Wiring incomplete |
Then a second panel was added so I could charge both the coach and chassis batteries. I later replaced the AGM batteries with LiFePO4. The chronology is included in this post.
Why Solar and LiFePO4 battery combination?
I think this is the ideal approach to keeping the coach battery charged and in best condition. Lithium batteries include a Battery Management System (BMS) which is electronics that monitors and controls the charging and the balancing of the cells. A battery has several cells, each of which when fully charged provide 3.65V of output. Four cells combined in the battery provide 14.6V at full charge, or a nominal 12.8 VDC. Each of these cells will charge at slightly different rates, and one of the duties of the BMS is to control this so that eventually all of the cells will be fully and equally charged, or "balanced".
Solar provides the energy to accomplish this, unattended. An alternate approach is to use a 120VAC charger, but that requires a power cord and access to a power outlet. My system does accommodate AC charging or charging via the alternator.
My Circumstances
My goals have changed since 2014. I have a 3-way refrigerator which can use propane but the controls are 12VDC. Some battery power is necessary for it, as well as lighting, etc.
Running the refrigerator on 12VDC and conserving propane is a primary goal. A secondary objective is running battery heaters on 12VDC when the vehicle is disconnected from shore power and in cold weather.
If 12VDC is selected for the refrigerator, the specifications indicate that 175watts or more are required. That's 13.5A at 13VDC. If I use 12VDC while travelling I can conserve propane. Of course I could connect the alternator to the coach, but the solar panel provides DC during stationary periods.
Before heading out on a trek we turn on the refrigerator ad pre-chill it. I can use 120VAC, but 12VDC is easier. The solar supports this.
I have no intention of living off the grid, but I might be off of it for a day or two. I had done some research and it requires about 300W to keep the Roadtrek battery charged when plugged into AC. Part of this is losses in the Tripplite charger. However, I did add a NOCO 10A charger with LiFePO4 mode. This more closely matched the battery manufacturer charge specifications. I can use either the NOCO or the Tripplite.
The battery manufacturer recommends charging at up to 20A and I'd prefer to charge entirely off of solar power at any time the Roadtrek is stationary and unused.
Procedure
This is an entirely "home built" and designed system. I've been using a 100Ah battery, but using newer, smaller LiFePO4 batteries I could install two 100Ah batteries in the original space. Real estate in a Class B is precious and I prefer not to use it for batteries.
Solar panel output and life decrease under higher temperature conditions. For that reason, mounting of the solar panel is important. My 210P has a fiberglass roof and it was tempting to "glue" the panel directly to the roof, as some do. However, that increases the panel temperature. It is better to mount the panel slightly above the roof, but that may increase wind resistance.
I decided upon a semi-flexible 200W panel, which was the largest that the Roadtrek roof could accommodate. I did not want to drill holes in the fiberglass roof, and that would have necessitated adding reinforcement. I instead mounted T-track to the roof using 3M VHB tape. The solar panel was mounted atop this. I also installed polycarbonate plastic panels under the solar panel. This provides a "sandwich" which slightly elevates the panel above the roof, supports the panel and promotes airflow beneath the panel. The wind resistance is slight.
I routed the solar wiring through the heat pump area, at the rear of the Roadtrek and avoided drilling holes for this in the roof.
The system installed accommodates using the rooftop panel or a portable panel. I installed a jack for a portable panel in one of the rear exterior bays.
I chose a better quality battery that does not include internal heaters. LiFePO4 batteries cannot be charged at below 32F. So, they must be heated in cold weather. I decided upon using external 120VAC and 12VDC heaters, independently controlled with thermostats. When it is cold and the coach is on AC power I use 120VAC to heat the battery. At other times I use 12VDC. When in movement I can supplement the solar and use the alternator to heat the battery.
The battery BMS assures that the battery does not overcharge of over discharge. I also installed a "Battery Protection" device. This monitors the battery voltage and automatically disconnects the battery if the voltage decreases to a preset low limit. The purpose is to disconnect the battery while there remains some energy, so that it will reconnect and provide power if necessary. I can control the settings using my Android phone.
The solar system charge settings are matched to the battery manufacturers requirements.
The installed system can provide 20A for 5 hours when off of solar (overnight) or about 8A for 12 hours. On solar it can provide about 15A continuously without draining the battery. The battery can function down to 10.4V, which is the voltage at which the BMS will disconnect the battery.
Chronology
2014: That first panel was a portable 30W solar panel to keep the engine battery charged. I stored the Roadtrek outdoors and there was no AC outlet available. Then I added a de-sulfating solar controller with portable 50W solar panel for the coach AGM batteries. My goal was simple: keep the batteries charged when stored outdoors.
2022: I made a major change in April & May 2022. I installed a better solar charging system for a larger 200W solar panel, replaced the AGM batteries with LiFePO4, and added both 120VAC and 12VDC heaters for the battery. Lithium batteries can't be charged at below 32F, so some type of heat is necessary for winter use; my coach battery is located outside the coach interior and is exposed to freezing weather. I continued to use portable solar panels.
I also installed a device to protect the battery from low voltage discharge. I used a setting of 11.80V as an automated cutoff. This is adjustable and lithium can tolerate deep discharges better than AGM batteries.
2025: I installed a 200W solar panel on the roof. Circumstances delayed this, and I decided to delay further until we completed our 2025 mult-month, 7,200 mile trek.
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I created several blog posts about this.
My goals have changed. I have a 3-way refrigerator which can use propane but the controls are 12VDC. Some battery power is necessary for it, as well as lighting, etc. If 12VDC is selected for the refrigerator, the specifications indicate that 175watts or more are required. That's 13.5A at 13VDC. If I use 12VDC while travelling I can conserve propane. Of course I could connect the alternator to the coach, but the solar panel provides DC during stationary periods.
Before heading out on a trek we turn on the refrigerator. I can use 120VAC, but 12VDC is easier. The solar supports this.
I have no intention of living off the grid, but I might be off of it for a day or two. I had done some research and it requires about 300W to keep the Roadtrek battery charged when plugged into AC. Part of this is losses in the Tripplite charger. However, I did switch to a NOCO 10A charger with LiFePO4 mode. I'd prefer to charge entirely off of solar power at any time the Roadtrek is stationary and unused.
In 2022 I added a Renogy solar charge controller. At the time I was using it with a portable solar panel. This was an entirely "home built" system of my design.
When I installed, I intended to put a solar panel on the roof in the future. It took a while to find the appropriate panel. Dimensions were the problem. I found a suitable 200W semi-rigid panel. I also purchased materials to fasten it to the roof, but I wanted it to "stand off". One issue with solar panels is heat. This can reduce power output and the life of the panel. On the other hand, I also want to minimize wind resistance.
I chose metal T-track to fasten to the Roadtrek roof. The roof of the 210P is fiberglass, and I didn't want to puncture it, or glue the panel directly to it. Instead, I purchased polycarbonate greenhouse panels, aluminum T-Track, 3M VHB tape and bolts.
The track is attached to the roof using the VHB tape. A polycarbonate panel can be set between the tracks to provide airflow and support the panel if one should lean on it. The panel is attached at eight points to the track using bolts, nuts, washers and lock washers.
Alternately, the polycarbonate can be installed above the T-Track. This raises the panel about 1/4 inch and aids airflow.
Circumstances delayed the project. The earliest I could have done this in Spring 2025, but decided to do it in the fall. So, here we are!
Solar Panel wiring will be routed through the air conditioner enclosure into the interior of the Roadtrek. I'll add a slot to the cover of the AC, but there will be no penetrations of the roof.
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