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Old 03-09-2017, 11:37 AM   #1
UnklJoe
 
2015 28' Flying Cloud
Box Elder , South Dakota
Join Date: Oct 2016
Posts: 101
Mounting Solar Charge Controller

We bought a 2015 FC 28 and it came with a Go Power solar kit (two flexible 100W panels, a charge controller and cables/connectors) laying on one of the beds. I have decided to install the kit myself and want to mount the solar charge controller on the wall above and to the left of the spice rack. (The overhead cabinet door will clear the faceplace when opening and closing the cabinet.)

The spice rack wall (for lack of a better term) seems to be about 2-1/2-to-3 inches thick (deep), (more than enough to mount the charge controller) and the refrigerator is "behind" the spice rack wall--but I don't know what's in the wall and don't know how to find out without removing the refrigerator....

I have read a LOT of posts on AirForums and have learned a TON of useful things. I have searched and tried to find any information about this wall, but have struck out. The kit instructions say to run the cables down through the refrigerator vent (which others in Airforums seem to have done) and I would like to do the same, which should make connecting to the charge controller relatively simple since the refrigerator is literally next to the spice rack wall. I'm hoping there will be an easy way to run the cables from the charge controller over to the battery bus bars from the spice rack wall, but my bigger concern before drilling holes and cutting an opening in the spice rack wall to mount the charge controller is how to know what's behind the wall?

My last concern is ventilation for the charge controller should I be able to mount it in the spice rack wall. I can't seem to find any spec's on what the heat dissipation is for the charge controller; I'll probably be emailing/calling Go Power soon if I can't find any other information.

My other possible location would be in the vertical wall below the lounge, which should provide ample air circulation as well as be closer to the battery bus bars--but would make reading the display difficult.

Any information is appreciated. Even tips/hints/tricks on removing the 'fridge, if that's going to be necessary.

Thanks in advance--and just wanted to say this forum is really, Really, REALLY useful and helpful. And, even funny on occasion!
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Old 03-09-2017, 12:10 PM   #2
Rivet Master
 
2015 30' Classic
Pleasanton , California
Join Date: Jan 2015
Posts: 745
If this was my installation I would do the following...

1. Reuse the existing solar pre-wiring and live with the 3% or less in losses that you could expect. It just makes the installation so much easier.

2. Mount the solar controller as close to the batteries as possibly, even if monitoring the display is impractical. I'd get myself a proper battery monitor like the Trimetric or Victron which include a shunt sensor. These monitors will tell you the state of charge of your battery and better guide you on your battery usage. The display from your battery monitor is really the only thing you need to consult. You could repurpose the existing CAT5 cable for this too.
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Old 03-09-2017, 12:22 PM   #3
UnklJoe
 
2015 28' Flying Cloud
Box Elder , South Dakota
Join Date: Oct 2016
Posts: 101
That Was My Plan B

Alano,

Thanks; this was my plan B. I'm somewhat leery of making the connection between the Go Power cables and the factory cables. I was thinking of using an un-insulated butt connector and a proper ratcheting crimping tool, and using two or three heavy-duty heat shrink layers over the connector.

I've seen conflicting information about the preferred location for the charge controller. While many charge controller manuals say they should be mounted as close as possible to the batteries there are many videos where it's not, I've read it's most important to have the inline fuse between the output of the controller and the battery positive terminal as close to the battery as possible. (Ain't 'lectricity fun?!?!?)
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Old 03-09-2017, 12:48 PM   #4
Rivet Master
 
2015 30' Classic
Pleasanton , California
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If you use the roof-top combiner box that's available from AM Solar, they include bus bars to make these connections.

The only reason manufacturers suggest mounting a solar controller near the battery is to reduce IR losses. It's more of a concern with an MPPT controller since the current charging the battery is greater than the current coming from the solar panels and therefore the IR losses will be greater. With a PWM controller, the battery charging current is the same as the current from the panels.

So if you want to repurpose the existing pre-wiring with your PWM controller, you could do this by placing the charge controller anywhere along the path of the pre-wiring. There's actually no advantage by putting at PWM controller near the batteries.

If you intend to run your own wires, I would suggest #8 AWG from the panels, to the controller and then to the batteries. And again, it shouldn't matter where you place your controller. A fuse is recommended at the output and a disconnect switch is recommend at the input. The only reason I suggested placing the controller near the battery is that the display information is redundant if you install a battery monitor.
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Old 03-11-2017, 05:41 AM   #5
Rivet Master
 
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2007 Interstate
League City , Texas
Join Date: Oct 2014
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Our solution may not bear direct relevance to your available choices because we have a different rig, but I thought I'd throw this out just as food for thought, thinking outside the box, to mix metaphors. Maybe give you some general ideas.

YES, we had big problems for as long as our OEM battery and our solar charge controller were separated by a long distance. That's one of the reasons why we reformatted our Interstate to move the battery (initially single) from under the cab passenger seat to become batteries (plural) beneath its closet floor. The solar charge controller, fuse panel, and all other electrical workings are now immediately adjacent at the top of the closet and in the overhead cabinet touching the closet.

We originally had a dead-head panel, essentially, at the end of the overhead cabinet that abuts the closet. All it held originally were some wire bundles and the DVD player originally installed by Airstream. We removed that cabinetry panel in its entirety and had a control center panel custom cut out of aluminum to replace it. These things are easily ordered on the internet.

Anyway, my point is, depending on how much elbow grease and $$$ you're willing to devote to it, you don't have to be constrained by putting a solar charge controller here or there. You can change things up entirely.

Here's what ours looks like - the charge controller is the ElectroDacus unit. We switched to lithium and so most of the rest of that stuff on the panel has to do with elective switching and redundant safety monitoring.

And yes, we did install a cooling fan in this assembly - my husband researched that and found the quietest one on the market. The handles that you see on the panel are for easily dismounting it from the neodymium magnets that hold it in its place.

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Old 03-11-2017, 09:07 PM   #6
UnklJoe
 
2015 28' Flying Cloud
Box Elder , South Dakota
Join Date: Oct 2016
Posts: 101
Quote:
A fuse is recommended at the output and a disconnect switch is recommend at the input. The only reason I suggested placing the controller near the battery is that the display information is redundant if you install a battery monitor.
I'm convinced I should use the factory wires and mount the charge controller below the lounge. And I want to put a two-pole disconnect in the input to the controller, but I can't find one of the nice red rotary switches with two poles that's not a 1-or-2-or-BOTH-or-OFF. Can you recommend a two-pole disconnect switch? (I don't want to use a two-pole breaker.)
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Old 03-11-2017, 09:26 PM   #7
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2022 25' Flying Cloud
NCR , Ontario
Join Date: Feb 2017
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I am an Elec Eng. Listen to those that state" place controller next to the batteries"

Power loss is = i**2 * R

compare
48V @10 A = 480W
vs
12V @40 A = 480W

For the same type of power cable , the power losses at the lower voltage are 16X that of those at the higher voltage, even those both initially provide the same power at source. That is why high transmission lines are at 500KV or higher is some places . The utility companies lose on average 20% of power in transmission loss. If they went with a lower voltage, the current would go up. Power losses are related to the square of the current.

The best RV solar solutions send higher voltage down to the controller primarily to reduce cables power loss
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Old 03-11-2017, 10:20 PM   #8
Rivet Master
 
2015 30' Classic
Pleasanton , California
Join Date: Jan 2015
Posts: 745
Quote:
Originally Posted by waninae39 View Post
I am an Elec Eng. Listen to those that state" place controller next to the batteries"

Power loss is = i**2 * R

compare
48V @10 A = 480W
vs
12V @40 A = 480W

For the same type of power cable , the power losses at the lower voltage are 16X that of those at the higher voltage, even those both initially provide the same power at source. That is why high transmission lines are at 500KV or higher is some places . The utility companies lose on average 20% of power in transmission loss. If they went with a lower voltage, the current would go up. Power losses are related to the square of the current.

The best RV solar solutions send higher voltage down to the controller primarily to reduce cables power loss

waninae39, with all due respect I'm also a EE. UnklJoe is placing two panels in parallel and using a PWM controller. So the voltage across both panels is 17.5 V when producing maximum energy. Because the controller is pulse-width modulated and not a MPPT controller, the current sourced from the panel is exactly the same at the current going to the battery. So, there's no advantage in placing the controller near the batteries in this situation.

A similar situation exists when GoPower/Renology sells you a portable solar kit. In these kits the PWM controllers are mounted on the back of the panels. The kits include a 15' extension and they typically offer an additional 30' connection. They get away with these configurations because there's nothing to gain by placing the controller near the battery.
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Old 03-11-2017, 10:38 PM   #9
Rivet Master
 
2015 30' Classic
Pleasanton , California
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Quote:
Originally Posted by UnklJoe View Post
I'm convinced I should use the factory wires and mount the charge controller below the lounge. And I want to put a two-pole disconnect in the input to the controller, but I can't find one of the nice red rotary switches with two poles that's not a 1-or-2-or-BOTH-or-OFF. Can you recommend a two-pole disconnect switch? (I don't want to use a two-pole breaker.)
Something like this would work fine. You only need a SPST (single-pole, single-throw) switch to break one of the legs.
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