Solar Power

[Terry Rosenthal]

Hello All,

    I have an old Class B, Dodge Motorhome that I recently purchased a solar kit for.  As you’ll be able to tell, I am not an expert on RV’s or solar energy, however, I’d like to ask a few questions.

    My Class B has the common dual battery setup.  One for the engine and one for the coach side.  As I drive, the engine alternator will charge both batteries.  I also have the 110 power hook up, with converter, for when parked, and again, this will charge the batteries.

   The solar kit that I purchased has the panels, wiring, and a charge controller.  My question is; can I simply  go through the charge controller and plug in to my 110 power hook up?  That way I utilize the converter and batteries that are already in my coach and I’m able to use all my power outlets. Then when parked, if wanted, I could simply unplug the solar and connect to 110???

    I value your expertise and opinion.  Thanks for any assistance.

[Lakota Wolf]

You won't be able to plug your solar panel controller to work thru your 110 volt input to your converter. I'm taking a wild guess that you possibly have 45 watt 12-18 volt panels with a digital solar controller box.

Your solar panels are best suited to keep battery (s) charged while off grid, meaning no access to shore power. When driving around keep your solar controller OFF and let engine alternator charge your batteries, and when your parked off grid and engine OFF, turn solar controller on,(during daylight hours), to keep battery (s) charged. Your basic solar panels aren't designed to be plumbed into an a/c voltage connection, since solar panels are designed on a d/c circuit design. Hope this helps with the available info you have provided. A lot of full timers use solar panels for when going off grid or camping where services are not available.

There are several members here familiar with electrical systems and solar. Maybe they will chime in with some more advice for you.  L.W.

[Terry Rosenthal]

Thanks for replying.   I have 3, 100w solar panels.  Yes, I purchased a solar kit so I can be off grid for a while.  It sounds like my solar power should be separate from the coach?  While driving around, the alternator will charge my coach battery.  Should I then connect that battery to my solar batteries, or am I utilizing my coach batteries as my solar batteries?  My solar kit has a digital control box. Should I purchase a converter to go in there with my solar kit?  Any suggestions for a converter and batteries?  Sorry for so many questions.  It seems like the more advice I get, the more questions I have.  Thanks so much!!!

[Lakota Wolf]

Terry,, look at this info,,,,, In the SEARCH bar, upper right corner,,,

Type in Connecting solar panels.

when topics come up,, scroll down to,Pro Solar Install.

Ton of useful info in this section of solar panels and wiring up to engine/coach batteries,

In my opinion, I would wire the panels to the controller,, and the controller down to the Coach battery, Your solar controller should be designed to cut power when a predesiganted voltage is achieved,

[Rich Thomas]

I agree with Lakota, in a nut shell the answer is NO. Unless you have a large solar system that operates through a DC to AC inverter to have a clean A.C. 120/30 volt output, you cannot plug it into an AC outlet. Typically these systems  are small and have a DC output to charge batteries and operate small equipment like a weather radio and charge phone batteries ect.. AC and DC circuits are not compatible in this situation.

[CH Smith]

Hi Terry, You might want to ck out the web site HandyBobs. The most informed about solar that I  have read. Although its a little hard to get past all of the complaining about the other installers. 

[Ralph Javins]

Good morning, Terry Rosenthal; 

     You did not say where the three 100 Watt photovoltaic solar panels are mounted, or even if they are mounted.  May I suggest that you consider your solar panel system to be associated only with the coach or house battery system.  You can attach the output of the solar panel charge controller (a solar industry name for a special purpose voltage regulator) to your coach or house battery system, and just leave it there.  As others have indicated, the charge controller will monitor the state of the coach or house batteries, and if it sees that the batteries are getting down, and it has sunlight, then it will charge the batteries.  This is one case where it is possible to install the accessory solar panel charging system, and you can leave it connected for automatic use when the conditions warrant.   A lot of the late model solar panel charge controllers are designed with 3 or 4 stage battery charging circuits ( I recommend them) and can be left on like this.  If you have only three solar panels, then you are probably running them in parallel as a nominal "12 VDC" system where the actual solar panel voltage with be in the 16 to 18 VDC range.  You can easily use one of the less expensive PWM or Pulse Width Modulated charge controllers.  The only time that you really need the more expensive MPPT or Maximum Power Point Tracking charge controller is when you are running a series connected solar panel system where the solar panel system voltage will be 32 - 36 VDC, or maybe even 48 - 56 VDC,  Do not wire more than three (3) nominal "12 VDC" solar panels in series.  Some very interesting regulations come into play if you try to do that on an RV electrical system.   At the three panels in series limit, you will have accomplished just about all of the benefits of the wiring power loss improvements that you are going to get from a higher voltage solar panel system. 

     Probably the main accessory to get for your coach or house battery system is a good battery system monitor, or at least a good digital voltmeter that will read out the voltage, say from 10.00 VDC up to 15.00 VDC for watching the battery voltage.  Yes, that will be a "four number display" (perhaps called a "3 & 1/2 digit" display) for the battery voltage.  With this kind of a voltmeter, you can watch the modern charge controllers and the "RV 12 VDC power supplies" drop the battery voltage back to about 13.20-13.30 VDC when the battery really is fully charged, and it drops back to that "float" or "maintenance" voltage to prevent gassing or "boiling" of the water in the battery electrolyte.  This does help to prolong the life of the coach or house batteries.  And when the electrical system is in use and pulls down the battery voltage, then the normal recharging algorithm picks up again to quickly bring the battery charge back up to full until it drops back to the "float" condition again.  A nice system.   And the finer voltage display gives you an earlier indication of the trend for the state of charge of the batteries. 

     Again, the last point is to have something mounted where you can see it easily and often to monitor with a good voltmeter what the coach or house batteries are doing.  Mine is in the galley or kitchen area right beside the main RV control and monitor panel, along with the clock, so I can see all of them. 

          Enjoy; 

          Ralph 

          Latté Land, Washington