Many people have been interested in the impact of solar panels on Advanced RV coaches. To help answer that question we conducted some measurements on the coach Gustav that is owned by Fred and Michelle Ahlgren.  Fred is a retired engineer who does engineering projects for ARV so he was in an excellent position to make these measurements.

Test Procedure

The day after the Summer Solstice was forecast to be a rare sunny day in Cleveland. Fred discharged the batteries in Gustav the night before so the batteries were able to accept solar charging. The van was parked with the front facing to the South in a driveway where it would get full sun exposure all day long.


Gustav is fitted with 3 of the ARV flexible solar panels, each of which is rated at 150 Watts. Each panel has a separate solar charge controller.  So the total installed power is 450 watts.


A computer was set up to record the current (amps) that were generated by the panels once a minute. This data was then used to calculate the amp-hours generated during the day.  The results are in Figure 1.




The blue line shows the amps generated by the three panels. The red line shows the amp-hours that were accumulated during the day.


This shows that for the daylight hours a little over 140 amp-hours were put into the batteries.



To put this in perspective we need to compare it to some other charging techniques. If the coach were being driven at 65 mph with the larger auxiliary Delco alternator that ARV is installing now, it would generate about 275 amps.  So in one hour of driving the batteries could accumulate 275 amp-hours.


If the van were plugged into a 30 amp shore power station, the batteries would charge at about 100 amps. So in two hours the batteries would accumulate 200 amp-hours.  Over night the batteries would be fully charged.


So solar is much less than either charging while driving or plugged into shore power.


The way to look at solar is to examine the impact it has on a parked coach that is not plugged into shore power. In this case the Silver Leaf, roof fan, and refrigerator will consume approximately 10 amps continuously.   The van will need 240 amp-hours to operate for a 24 hour period.


The standard 800 amp-hour battery pack that ARV installs has a battery shutdown feature that is set prevent the batteries from being discharged below 20% of capacity. This is needed to protect the Lithium batteries.  So the batteries can supply a total of 640 amp-hours if they are fully charged at the start.


If the coach is parked without any external charging it can sit for about 2.5 days before the batteries are depleted. With the addition of solar, the batteries would be charged an additional 140 amp-hours per day.  Only a net of 100 amp-hours would need to be supplied by the batteries.  So the van could sit for about 6 days and maintain the Silver Leaf, roof fan and refrigerator.


Of course this all depends on the weather and other factors. The data was taken in Cleveland where even on a sunny day the lighting is not as intense as in the southwest.  So we could expect more solar charging in better locations.  Also if the inside of the van gets very hot, the refrigerator will need to work harder and will consume more power.


15 replies
  1. Mike Stanley
    Mike Stanley says:

    Thanks for this analysis. And I am particularly happy that the test was conducted in Cleveland, rather than the southwest. I appreciate the comparison to the 2nd alternator and shore power.

    • Mike Stanley
      Mike Stanley says:

      I gather that one should turn off the inverter if you have good sunshine but no shore power and aren’t going to drive anywhere in order to get that 6 day stretch.

  2. Michael Witte
    Michael Witte says:

    What is the practical maximum solar power, in terms of watts, ARV could install on a Sprinter top?

    and would this effect the other support systems for solar?

  3. Brent
    Brent says:

    I assume there are some losses in the system between the solar panels and the batteries. The article states that the test measured the amp-hours “generated”. So, how much of the generate power reached the batteries? Maybe a better question is where was the measurement taken? Near the solar panels before system losses or near the batteries after system losses?

    • Janice Spicuzza
      Janice Spicuzza says:

      Thank you for your question, Brent. The measurement was done at the solar charge controller outputs. Our system has a separate charge controllers for each of the three solar panels. These three measurements were summed to produce the result.
      There is a direct wired connection from the controller outputs to the battery. So no current is lost.

  4. George
    George says:

    The article mentioned that on a hot day, the unit would heat up and the frig would have to work harder. Would you expect the solar on top to reduce (at least a little) the heat build up inside as the sun is hitting the solar cells not the van roof directly?

  5. Ben Allen
    Ben Allen says:

    I appreciate the information on the impact of solar panels on a caravan. I had no idea that solar panels could cause the life of the battery to last so much longer than without the panels, I never knew they provided so much of a charge. My dad has been looking into getting an RV and putting solar panels on it, I will be sure to share this information with him.

  6. Chuck
    Chuck says:

    I’m in the market for a 2013 CS adventurous or a 2013 RS adventurous and was wondering what the cost of retrofitting these vehicles with Solar supplying around 300 W of power?


    • Janice Spicuzza
      Janice Spicuzza says:

      Thank you for your question Chuck. We need some more information about what is on top of your roof. Can you give us a call at 440-283-0405. Alternatively, you can send us an email through our contact page to start an email conversation.


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