Solar Panel Wiring

[Passin__Through]

Is regular automotive primary wire suitable for use between a solar panel and the charge controller? I am installing two, 100-watt poly panels on the roof of my 5er, running the wires down a holding tank vent pipe, then to the controller. My plan is to wire the panels in parallel, then utilize the 10AWG automotive primary wire after the Y-connector.

My thinking is that automotive primary wire would be easier to work with as it is more flexible than the wire coming from the solar panels. It is also much less expensive than solar panel extension wire. I am aware I will need male and female MC4 connectors for the primary wire.

I have never done this before, so thank you in advance for your sage advice.

[westend]

Passin' Through wrote:

MEXICOWANDERER wrote:
Remember to use only black cable ties and black plastic clamps. They withstand sunlight and heat a lot better.

Thanks for the tip.

I happen to have a roll of Eternabond on the way. What do you think of using some of it to secure the wires to the roof between the panels and the vent I will use to route them to the basement? The run to the vent is about 3 feet.

You need to secure the wire so wind/ travel speed doesn't interfere with it's positioning. Eternabond will probably hold MC4 down to an EPDM sheet, especially a short run of 3'. There are wire clamps,holders that could be fastened to hold the wires but I understand the fear of putting even a small hole through the membrane. I would have no problem with that since there are such good sealers available and aren't the brackets for the panels fastened through the membrane? That's just rhetorical.

[Passin__Through]

MEXICOWANDERER wrote:
Remember to use only black cable ties and black plastic clamps. They withstand sunlight and heat a lot better.

Thanks for the tip.

I happen to have a roll of Eternabond on the way. What do you think of using some of it to secure the wires to the roof between the panels and the vent I will use to route them to the basement? The run to the vent is about 3 feet.

[MEXICOWANDERER]

Remember to use only black cable ties and black plastic clamps. They withstand sunlight and heat a lot better.

[Searching_Ut]

I have 5 of the Grape solar panels on the roof of my fiver, and 6th to install if/when I ever get the rig back out of the shop. mine are flat mounted on the roof. I installed them earlier this year, and haven't used them in any cold temps yet, but the average mid day output has been pretty consistently right around 5 amps per panel. They generally maintain that output for 2 to 3 hours, with slow drop offs on either side of mid day. Shade, clouds etc of course result in less, sometime considerably less.

[westend]

Having solar take care of your batteries while in storage is one of the best aspects of solar charging.
I have a Morningstar controller and am impressed with it's reliability and function. It is the MPPT-15.

[BFL13]

Ha! My cranial density is more than yours, so take that! 🙂

[Passin__Through]

BFL13 wrote:
With PWM you get the Isc of the panels. So your two together can do 12.26 amps aimed at a high sun. You should allow some margin for panels when they are cold doing more than their rated amps, rated at 25C/77F

Flat panels don't get as much light as aimed panels, so do less than rated amps. A 15 amp controller should give you enough margin, but a 20 would be better for more margin.

From panels to controller should be #8 as stated above. However since you hardly ever do any off-grid, it is not worth the extra money if that is a consideration over #10.

In fact for that much off-grid you just need an extra battery for that trip, and no solar at all.

My panels are mounted flat and are not able to be tilted. I will just have to live with the power loss because of it.

If Morningstar made a 20-amp ProStar controller, that would probably be perfect for my setup due to the extra capacity. I've read lots of positive comments about Morningstar controllers so that is why I plan to use one. I know there are lots of 20-amp units for sale but don't know enough about them to take a chance. Something about "magic blue smoke" that others have experienced from time to time that just does not excite me.

Even though I rarely go off-grid there have been times when solar would have eased my mind about power. Thus my adding it now.

Another plus of course will be no longer having an extension cord between the trailer and the house to keep the batteries charged.:)

Thanks for your information. I am trying to learn something from all the comments that have been posted in the various threads about solar power. It is kind of tough sometimes, due to cranial density.:)

[Passin__Through]

mike-s wrote:
I got a PS-30M, not because I expect more than 15A of panels, but because it allowed me to wire the trailer loads through the controller without exceeding its capacity.

That lets you monitor your current load using the controller's meter. With everything on (fans, lights, fridge, furnace, etc.), my total load could potentially go over 15 A. Some people wire them in with just the panel and battery connections, which is fine, too - you just lose the ability to monitor the load.

The PS meter show battery voltage, solar current, and load current. If you know both currents, it's just a matter of subtraction to know how much current is going into the battery, which I find useful. The battery current is not included in the displayed load current.

Plus, the 30 A one is only about $20 more than the 15 A one when I was shopping. I'm not aware of any advantage for the 15 A one, other than price.

edit: definitely plan on using the remote voltage/temperature capabilities of the controller. Your battery will appreciate it.

Thanks mike-s. I understand the "bigger is better" concept with solar and components but for my purposes the 15-amp controller should do all I need it to. The extra bit of loss in 10AWG vs. 8AWG wire doesn't bother me too much so I will be buying the cable you previously recommended.

I do plan to use the remote voltage capability, and a remote temp sensor is definitely on the horizon.

Again, thanks for everyone's assistance in this modest endeavor.

[BFL13]

With PWM you get the Isc of the panels. So your two together can do 12.26 amps aimed at a high sun. You should allow some margin for panels when they are cold doing more than their rated amps, rated at 25C/77F

Flat panels don't get as much light as aimed panels, so do less than rated amps. A 15 amp controller should give you enough margin, but a 20 would be better for more margin.

From panels to controller should be #8 as stated above. However since you hardly ever do any off-grid, it is not worth the extra money if that is a consideration over #10.

In fact for that much off-grid you just need an extra battery for that trip, and no solar at all.

[mike-s]

I got a PS-30M, not because I expect more than 15A of panels, but because it allowed me to wire the trailer loads through the controller without exceeding its capacity.

That lets you monitor your current load using the controller's meter. With everything on (fans, lights, fridge, furnace, etc.), my total load could potentially go over 15 A. Some people wire them in with just the panel and battery connections, which is fine, too - you just lose the ability to monitor the load.

The PS meter show battery voltage, solar current, and load current. If you know both currents, it's just a matter of subtraction to know how much current is going into the battery, which I find useful. The battery current is not included in the displayed load current.

Plus, the 30 A one is only about $20 more than the 15 A one when I was shopping. I'm not aware of any advantage for the 15 A one, other than price.

edit: definitely plan on using the remote voltage/temperature capabilities of the controller. Your battery will appreciate it.

[Passin__Through]

Thanks for the replies and suggestions.

The cable in the link provided by mike-s would suit my needs best, I believe.

Just for some background, my panels are Grape Solar GS-100 watt that I ordered through Home Depot.

Here are the specs from the Grape Solar website:

Max System Voltage (IEC/UL) 1000V
Maximum Power Pmax 100 W
Listed PTC Power 100 W
Voltage at Maximum Power Point Vmpp 18.0 V
Current at Maximum Power Point Impp 5.56 A
Open Circuit Voltage Voc 21.9 V Short Circuit Current Isc 6.13 A
Module Efficiency 14.63


I plan on using a Morningstar ProStar PS-15M PWM controller to feed my two GC2 batteries.

Two-hundred watts of solar is all I anticipate needing since the vast majority of our "camping" is in sites with at least electrical hookups. Once a year I boondock by myself for 5 or 6 nights. The main electrical draw is for the fridge, and use of the LED lights is minimal as is furnace use.

Due to very judicious electrical use I have not yet run out of battery power when boondocking, and the solar power will help insure I don't. It will also keep the batteries topped-up when in storage at home, without the need of stringing a extension cord.

Does anyone see any potential difficulties with the use of only a 15-amp controller for 200 watts of solar, given my rather simple needs?

[time2roll]

+1 for using MC4 cable that is made to resist the elements.
Yes it is a little more $$ and not exactly fine strand. Once pulled into place it will be best in the long run.
As said get an extension cable of twice the length you need and cut in half. Connectors to the panel, cut end on the controller.

[YC_1]

Heavy duty landscape wire will handle the current and weather. It is designed for plenty of current and the wire covering is excellent.

[2oldman]

You can cover indoor wire with something like Heng's rubber roof coating, or eternabond tape to protect it.