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Old 02-10-2013, 11:38 PM   #1
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Solar, 4 awg, 28ft, -- ok??

I've been racking my brain trying to find the best way to put the 4 solar panels I bought onto my camper and think I have found my answer. The camper is a toy hauler and what I plan on doing is have the panels hang down over the ramp for the toy hauler. The panels will swing out and up btw, letting the ramp come down.

The only problem to what I think is my solution is the distance of the wire run.

My panels: panels - 4 x 145 Watt @ 18 volts x 7 amps each. (DMSOLAR on Amazon)

My plan: 2 sets of 2 panels in series run to a combiner box at the panels. Then from the combiner box 28ft to the charge controller. So, 36 volts @ 14 amps running 28' on 4 awg wire to the charge controller.

I've run it through a voltage drop calculator and wanted to verify the numbers. It didn't look bad at all but I'm still very much green at this stuff.

The below is what I get running copper 4 awg 28ft @ 14 amps and 36 volts. If this is right I'm pretty happy.

Votage drop: 0.19
Votage drop percentage: 0.53%
Votage at the end: 35.81
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Old 02-11-2013, 07:29 AM   #2
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that's real good number drop wise.

make darn sure the Vopen of the combined panels isn't going over what the controller is rated, Vmax. (I think those are the right acronyms)
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Old 02-11-2013, 09:16 AM   #3
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It does look like a pretty good number. I was looking at the back of the camper this morning and realized I'll probably have to add another 4-5 feet to that.

Actually I was thinking those numbers looked too good. Thought I had done something wrong. Could somebody verify what I was looking at was correct?
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Old 02-11-2013, 09:20 AM   #4
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Quote:
Originally Posted by apollumi View Post
I've been racking my brain trying to find the best way to put the 4 solar panels I bought onto my camper and think I have found my answer. The camper is a toy hauler and what I plan on doing is have the panels hang down over the ramp for the toy hauler. The panels will swing out and up btw, letting the ramp come down.

The only problem to what I think is my solution is the distance of the wire run.

My panels: panels - 4 x 145 Watt @ 18 volts x 7 amps each. (DMSOLAR on Amazon)

My plan: 2 sets of 2 panels in series run to a combiner box at the panels. Then from the combiner box 28ft to the charge controller. So, 36 volts @ 14 amps running 28' on 4 awg wire to the charge controller.

I've run it through a voltage drop calculator and wanted to verify the numbers. It didn't look bad at all but I'm still very much green at this stuff.

The below is what I get running copper 4 awg 28ft @ 14 amps and 36 volts. If this is right I'm pretty happy.

Votage drop: 0.19
Votage drop percentage: 0.53%
Votage at the end: 35.81
In the "files" section there's a chart for what your seeking.
Files section right next to "user cp"

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Old 02-11-2013, 09:23 AM   #5
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Old 02-11-2013, 02:15 PM   #6
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just ran your #'s, 36v, 15a and 10 meters. about .75 %. you could go a size smaller and save some $. #6 wire will get you about 1.1% drop. still great.
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Old 02-11-2013, 03:43 PM   #7
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just ran your #'s, 36v, 15a and 10 meters. about .75 %. you could go a size smaller and save some $. #6 wire will get you about 1.1% drop. still great.
Yeah, might do that. I just called a company locally and # 4 awg is $2.00 a foot. So I'd be looking at $120.00 or close to it.

I noticed my battery cables only has the "+" side going to the convertor (current setup) and the "-" goes to the frame. Is this the norm? Can I just connect the negative wire to the frame? I was thinking I'd have to bring all of the wires to a common post for positive and negative connections as well as the inverter. I was also thinking I would need a ground wire coming off of the solar panel frame to the frame. Everything with fuses, etc.
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Old 02-11-2013, 07:37 PM   #8
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both wires must run from panels to controller and NOT be connected to anything else. they should be fused.

I know using the chasis for negative is commonplace for 12v systems. Doing so will add additional impedance in the negative leg of the controller causing problems. remember that thing you just calculated, voltage loss? Steel doesn't conduct electricity nearly as good as copper. In autos, I don't think there's a 30' run anywhere, so loss will be minimal.

If you run your copper wire to the battery, you are setting yourself up to install a shunt for a battery monitoring system. On those systems, positive current is not measured. Only the negative side passes thru a shunt. All negative current must be measured.

here's a basic schematic of my system. Take it as a guide, as there have been some corrections/changes made since I drew it up.


dang it, it posted upside down, sorry.


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Old 02-12-2013, 11:12 AM   #9
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Cool. I just didn't know if using the frame was best or not. Or, if it might be necessary due to how the convertor was wired, etc..
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Old 02-12-2013, 08:25 PM   #10
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yes, there must be a wire from negative to frame, just don't use the frame as a primary current conductor. The frame needs to be tied to negative for things like running lights to work...at least on my aluminum skin trailer.
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