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Sat Jul 10, 2010 9:14 pm

First off....my apologies if this has been covered somewhere. I searched a bunch and haven't found an answer.

I have 2 solar panels and my plan is to have a 50w permanently mounted to the top for when I'm driving and then a 2nd 85w that I can put in the sun while I park/camp in the shade. My idea for the setup is to have 2 terminals posts (one + and one -) that has the 50w permanently connected and then I can connect the 85w when in use. So when I'm camping I'll have 3 wires (all of appropriate gauge, of course) connected to the terminal posts: 1) to 50w panel 2) to 85w panel 3) to charge controller. I figure this should work since the panels have diodes.

Will this setup work? Anything that I'm not considering?

Sat Jul 10, 2010 10:11 pm

I will depend on what the controller can handle. I would put some kind of dump load on there so excess power won't damage anything. Something like a fan in the van etc....

Sat Jul 10, 2010 10:39 pm

Thanks. Not sure I understand the fan reference. Both panels together will only put out about 7-8 amps (assuming both are in the sun which will probably seldom happen) and the charge controller is rated at 10a. Is my plan correct wiring? All + to one terminal post and all - to the other terminal post. I've done some pretty extensive wiring so far and had no problems, but that's probably because I've planned everything out in advance.

edit: I think I understand the dump load reference now...as in a load connected to the charge controller.

Sat Jul 10, 2010 11:50 pm

My understanding is that you need to connect the two panels together to make one output. Make sure your controller can handle the combined load. You can put the panels in parallel if the nominal output voltage is the same for each panel, if they are different you cannot combine them on the same charge controller because one panel will try to backfeed into the other.

Sun Jul 11, 2010 5:25 am

I'm doing the exact same thing as we speak.

There are two ways to hook up panels just like batteries. You can parallel them or hook them up in series. By hooking those two panels in series you get a 24 volt system instead of 12 which you don't necessarily want for an RV situation. In parallel you double the amperage output while keeping the system 12 volt. In actuality those panels alone will produce about 15-18 volts and anywhere from 2-4 amps. The voltage is well high enough to keep batteries properly charged.

I'm installing one 60 watt panel inside the cargo portion of the Westy with a tilt function when I need it. The wire will run from the outside of the van to the inside and will hook up to a distribution block (- to - + to +). I'm going to place a permanent two pin connector inside the water fill hookup to reduce drilling holes in the van. That wire will run to the same distribution block (- to - + to +) that runs to the charge controller. When I need more juice for extended camping I can plug in the second 60 watt panel and place it directly in the sun.

Here is a good link for various solar info.

http://www.freesunpower.com/

Just a note about diodes. My panels require that I connect the diode differently depending on if they are in parallel or serial. You might want to verify how yours work. You definatley don't want parasitic drain at night or low light situations.

Sun Jul 11, 2010 10:32 am

Diodes in PV circuits are, like, Pleistocene technology. Your charge controller will isolate the panels whenever they do not provide charge and prevent reverse current discharge at night. ANY charge controller sold today provides this protection, it is one of the most basic and essential features. Diodes cost current, you want them gone, and your charge controller renders them redundant.

Quote: So when I'm camping I'll have 3 wires (all of appropriate gauge, of course) connected to the terminal posts: 1) to 50w panel 2) to 85w panel 3) to charge controller. I figure this should work since the panels have diodes.

Will this setup work? Anything that I'm not considering?

I take it you mean three wire pairs, not three wires. If so your concept is correct. You will have a wire pair from your charge controller's battery output connections to the battery, plus and minus. On the PV input connections of the CC, you will have two pairs connected in parallel, one to each panel. Either or both panels can then be connected at any time. The fact that the panels are of different wattages doesn't matter except with an MPPT-type CC, which I doubt you have at this small size. They must both be wired to produce a nominal 12V (some panels can be wired for either 12 or 24), and their amperages added together must be lower than the maximum rated amperage of your CC, as was already pointed out. So long as those conditions are met, and wire sizes are sufficient for the amperages on each circuit, you're good to go.

And drop the diodes.

Sun Jul 11, 2010 12:20 pm

Good to know info about Diodes. I'll yank mine and see if it helps my current throughput.

Sun Jul 11, 2010 12:28 pm

tencentlife wrote: And drop the diodes.

Interesting, I might just give this a try. And yes....I meant 3 wire pairs. And no, I don't have a mppt controller.....yet. :)

Sun Jul 11, 2010 1:35 pm

This is the controller I'm using. I like the fact that I can charge two different battery banks leaving my future options open. The remote digital panel makes for a clean and useable install.

http://www.morningstarcorp.com/en/sun-saver-duo

Sun Jul 11, 2010 7:41 pm

Does anyone see any change in effects from these two scenarios?

A) Having both panels connected to the distribution posts with a 3rd wire pair going to the CC, vs.

B) 2 wire pairs going to the PV input on the CC, 1 pair directly to the rooftop panel and the 2nd pair going to the distribution posts for connect/disconnect of the 2nd panel

Either setup will accomplish the same goal for me.

Sun Jul 11, 2010 9:56 pm

I've done quite a bit of wiring with multiple batteries and solar panels, but it's difficult to follow your description without a visual. Do you have a schematic to post and take a look at?.

Sun Jul 11, 2010 10:20 pm

Yeah...tried to take a shortcut. FAILURE!! :oops: I'll write a simple schematic and post it tomorrow.

Mon Jul 12, 2010 1:15 pm

Okay, so here's a simple schematic. I just want to know if one choice is better than the other.

Mon Jul 12, 2010 4:01 pm

A makes more sense to me

Mon Jul 12, 2010 6:55 pm

madspaniard wrote: A makes more sense to me

Why is that?

Mon Jul 12, 2010 10:01 pm

What I did was similar, but I connected my solar panels to the charge controller, then connected the charge controller to some distribution posts, then connected the batteries to the posts. Grounds can all be common. Either way, your "A" scheme looks like the way to go with what you're suggesting.

Mon Jul 12, 2010 10:07 pm

WSideWitneSS wrote: madspaniard wrote: A makes more sense to me

Why is that?

It makes more sense to do as in Option A and have the distr post doing its job for both panels (connect/disconnect panels when needed)

Thu Jul 22, 2010 12:43 pm

So far so good. I have the 50w mounted on the top and I can connect the 85w as needed. I also now have all 3 batteries connected with yandinas allowing all batteries to be charged via alternator, A/C, or solar. :D :D

I tell you...drilling that first hole in the fiberglass top is a heartstopper. I measured and measured and measured and was still scared. I think it turned out really well though.

Here's my rat's nest of wiring right now. I 'll clean it up pretty soon and hopefully find a better and more permanent spot for the terminal posts / disconnects.

Thu Jul 22, 2010 3:06 pm

I choose option A, although mine are both permanently mounted.

Thu Jul 22, 2010 6:13 pm

I am running a 130W Panel through a Charge Controller (CC). I am also going to install the GW Aux Battery Kit. Can I wire the Aux Battery kit directly to the battery or do I have to go through a CC. Reading the GW Instruction (No Solar Panel), I can hook up directly to the battery.

Any advice?