Forum Discussion

sushidog's avatar
sushidog
Explorer
Aug 24, 2015

Has anyone ever mounted solar panels to a tow vehicle?

I want to build a rather heavy solar system for full-timing in a travel trailer (actually 2 separate systems, a 12v and a 48v one). However finding TTs that will carry this much weight are hard to find and limit my choices considerably.

I was just toying with the idea of mounting some high voltage solar panels and 48v battery bank on a pick-up truck rack over my bed topper. As a side benefit, the panels would act as a giant wind deflector, increasing fuel mileage when towing. I would mount 4 - 435 watt Sun e20 panels on the rack at a 9-10 degree angle to deflect wind over the top of the camper while towing. I could also hinge the front to lift them to a higher angle into the sun when stopped (possibly with an electric jack.) Another advantage this would give me is I could park the camper in the shade, in the best direction that suits the location, while the truck could be positioned where it would collect full sun. If I use the 435 watt Sun panels, they would overhang the sides of the truck by about 4" on each side and about 8" in the back. If I use the smaller 300 watt Sharp panels instead they would fit with only a couple inches overhang either way, but probably wouldn't deflect the wind quite as well as the bigger panels would. If the 300 watt panels are used, I would need to add 2 folding panels, (for a total of 6 - 300 watt panels or 1800 watts vs 4 - 435watt panels for 1740 watts) one on each side, which would hang vertically when traveling and be raised so they are flush with the others stopped. I would have the charge controller and inverter in the truck bed, near the battery bank. An 8 ga heavy duty 25ft extension cord should be more than enough to carry 12 amps of 48v DC power needed to power my 48v native mini-split heat pump. I would also add a 30 amp female electrical receptacle mounted on the back of the camper to plug my trailer's shore power cable into for my inverted 110v AC needs. Another advantage of my plan, other than to remove about 900-950 lbs of weight off the trailer, (at the expense of 1,000 lbs added to the bed of the truck, which should be OK as I have a 3/4 ton with enough reserve) would be to allow easier access to the solar panels for cleaning and maintenance without climbing on the roof of my TT. Plus the additional weight and expense of building a tilting solar panel rack will be offset by the cost and weight savings of having fewer solar panels producing higher output due to tilting.

Here's a drawing of what I'm talking aout:


Has anyone seen or done something like this? Does anyone see any major drawbacks in my plan?

-Summary-

Advantages:

1. Removes 900-950 lbs from the trailer.

2. Starts with 10 degree panel angle (great for RGV in summer) and allows easy panel tilting for harvesting more solar power, especially in winter and higher latitudes.

3. Facilitates panel cleaning, and battery access - lower is safer

4. Allows panels to act as big wind deflector making towing easier and improving mpg.

5. Panels shade truck and topper, keeping it cooler inside.

6. Travel Trailer can be parked in the shade (or mostly so) so it stays cooler inside trailer, requiring less AC.

7. Truck can be easily positioned for maximum solar harvest at different times of the day and year.

8. Avoids putting extra holes in roof of TT to mount 4-6 panels (plus saves roof space).

9. Increases storage space inside TT by moving batteries, controller, meter and inverter to truck bed.


Disadvantages:

1. Adds 1,000 lbs to the truck which will reduce MPG when not towing. (Will offset MPG gain when towing)

2. Takes up some additional space in truck bed to house batteries, controller and inverter.

3. Any more?

Thanks for your help and advise,

Chip

35 Replies

  • sushidog wrote:
    If I'm using an electric jack or a slide out motor that draws say 40-50 amps, then I would have to get two of these..
    I have a Victron 24->12 voltage reducer on my 24v system. Pot adjustable where I keep it at 12.5vdc. At 25a (and $100) it runs my slides just fine. Victron makes these for 48vdc also.. a little difficult to discern from their website but it's there. I've never concerned myself with efficiency - I'm not sure what that matters.

    I was also looking at this one for my future needs which should suffice.

    The largest off-coach power setup I've seen was in Quartzsite a few years ago. Probably 2,000w of panels on tiltable mounts, 16 6v batteries, humongous inverter on the bed of a Class 8 tractor. The guy had no trouble running his air with it.
  • 2oldman, I've looked at the 48v-12v converters, and this may be an option rather than a stand alone battery system, and a 300 watt solar panel to keep things happy, however they are expensive and suitable for low current draws. If I'm using an electric jack or a slide out motor that draws say 40-50 amps, then I would have to get two of these: http://www.amazon.com/One-Golf-Cart-Converter-36V/dp/B00LPHGM40 for about $120 plus suffer the 85% conversion efficiency. they do make ones that are much more efficient but one could easily buy a battery much cheaper and have the additional power it provides for running your 12v stuff. My 48v would be strictly for my heat pump and inverter use, which would be 85-90% of my power needs.

    I'm planning on starting with a "learner" bank of 8 CG-2 (golf cart batteries) from Sams. At only $85 each my battery bank will only set me back $680. This should get me by for about 3 years if I don't kill them first. I would like my next set to be LiFEPo4s, if the price drops by then to reasonable levels. If not I will either go with a set of Rolls S-550s which will cost about $2,616 at today's prices but should last another 10+ years - for roughly the same cost/year but at twice the capacity of cheap of cart batteries. Or I'll go with the new Trojan T-105 REs that are now available with the same estimated life of the Rolls/Surrettes, but at $1,400 for a set of 8 for 225 amp/hrs (vs 460 for the Rolls) is another option. I have time to wait and see if they perform as advertised before I decide which way to go.

    Trackrig, thanks for the link!

    Chip
  • I'm not sure where the 12v system comes in.. but you can get a 48v inverter, and a 48->12v converter for the TT's needs. I'm going to do that soon.

    Sounds like a great plan, I like it. What is your battery bank?