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Old 04-01-2012, 09:48 AM   #1
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solar panels and tow vehicle

I am in the process of installing a solar panel system in my 2000 Cherokee. As I do so, I keep realizing there are more and more things I haven't given thought to. Most of the time I am able to find the answers by researching on-line but not this time. here goes..

Do I need a blocking diode to prevent the solar panels from backfeeding to my truck?

I have a 2007 Tundra with the big V8, a Prodigee brake controller and of course my 2000 Cherokee. I'm worried that while towing, the charge controller would go into bulk mode and the higher voltage might somehow damage the brake controller or my truck electronics. I've always unplugged the camper from shore power before hooking up to my truck as a precaution. Any thoughts?

I'll post pictures of the install when completed.
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Old 04-01-2012, 10:46 AM   #2
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I am at a loss. You plan on connecting the panels and its controller to the truck's electrical system?

Now THAT is risk taking. (May even be "chance" taking!)

If I was doing what you are trying to do, I would just have a long DC extension cord to hook up to the camper when we are in camp or use the unused "AUX" pin (the center one on most 7 pin Bargman connectors) to connect the panels to the trailer while connected but without the engine running. When the engine is running (key "ON") the alternator is connected to the camper. I think you would also need a "kill" switch to the aux power and remember to turn off the panel controller before you started the engine.

IMO, trying to fix keep the panels from feeding back through to the trucks alternator and starting battery with a blocking diode would require a fairly large capacity diode to handle say 30 amps or more the panel controller is capable of putting out.
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Old 04-01-2012, 11:57 AM   #3
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You'll be fine.

There is already voltage potential on your truck's electrical system from the battery. And most likely from your converter when plugged into shore power. Its trying to charge your trailer batteries and of course your truck battery through the trailer plug.

You also do basically the same thing when you hook up jumper cables from another vehicle.

And, while you are towing and your alternator is running, the charge controller will see 14-18 volts and not try to charge anything.

I do have a question for you. Are you installing a shutoff on your panel array? I mounted my solar charge controller and started running the wires. I realized that if I had to do any work on the system, I'd have to climb up on top of the trailer and put some cardboard or blankets on the solar panels. I thought maybe a shutoff switch right there would be safer. Also, are you fusing the solar power lines near the panels?
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Old 04-01-2012, 12:07 PM   #4
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Hey herk.I think his concern is that with the solar system on the trailer hooked to the trailers batteries,it would would feed to the truck and cause damage to the electronics in the truck.If this was a problem,the solar panel companies would include a diode in the kit.So no,there would be no problem without a diode.

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Old 04-01-2012, 12:53 PM   #5
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I'll be watching this thread, and looking forward to the pictures.
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Old 04-01-2012, 02:22 PM   #6
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You'll be fine. It makes no difference where a 12v power supply to the batteries comes from, or even if it comes simultainiously from multiple sources. If properly wired, you can charge your batteries from the solar, from the built-in "factory" inverter, or from the 12v suply from he tow vehicle. The tow vehicle supply is the least effective, due to wire size and length of run.
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Old 04-01-2012, 07:24 PM   #7
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Rod,

Yes I'm using finger safe fuse attachments on the fuse block. I have limited space where the controller is going. I wish I had space for the knife switches and fuse blocks. Check out the picture.

You bring up a good point about the voltage from the alternator shutting off the charge controller. Thats another problem. It would be more efficient to charge from the panels from solar while traveling instead of the 10amp limited power from the truck.

I spent the day running the #4 wire. Of course nothing could go easy, first I had to move the radio antenna, then I had to drill up thru a wall in order to get to the junction box (without damaging the wall board). I ran the cables from the junction box thru the hole where the antenna was originally located, down the inside of a wall and into the area where the charge controller is located. In the middle of all this I accidently stabbed my arm with a knife resulting in a pretty bad gash. To top it all off, one of my wife's students was helping me so I had to behave and not let any bad words slip.

Oh, this is a not a kit system. I didn't like the prices of kits nor did I like the specs on most of them. So everything is "piece meal" but not junk.

thanks for the help everyone.
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Old 04-01-2012, 09:08 PM   #8
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Quote:
Originally Posted by Buffalohunter View Post
I'll be watching this thread, and looking forward to the pictures.
Indeed, this is very interesting.
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Old 04-01-2012, 09:29 PM   #9
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Quote:
Originally Posted by RonLynnJr View Post
Indeed, this is very interesting.
Ditto; on the very interesting.
While not convinced (I do have a hard, and opinionated, head), I will stand by to see how this all works out.

Without a key in the ignition there is no path from the trailer plug to the vehicles batteries due to the relay in the engine compartment fuse block.

Current is only supposed to flow from the alternator to the truck batteries and the Bargman plug when the engine is running. Current will not flow from the truck batteries to the camper or vice versa with the ignition key off.

If the camper is plugged into shore power and you connect the camper to the truck via the Bargman connector; the truck's battery should not charge. Easy to check and I will tomorrow. Since camper is in the driveway and the truck is in "Pre-Contact" position and easy to plug in. 13-14 volts or so should show up on the battery if Rod is correct.

Could I convince you to post a wiring diagram of your proposed installation? Always interested in learning something new.
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Old 04-01-2012, 09:31 PM   #10
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count me logged into this too .. cause i am really scatching my head ..
please at least give us the specs on the RV .. it could be a tent trailer for all i know..

d-mo
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