Adding solar this simple?

[Tom48]

Originally Posted by corn18

Just from a wiring perspective, it seems adding solar is fairly simple. Am I missing anything?

Current:



Add 2x200W panels and 40A MPPT charge controller:

I usually put the solar charger + lead, on the Battery side of the Master cut off switch so batteries always charge. Not good to shut off battery with solar PV circuit still live. We had one lady we installed about 4 years ago fry the display in her PWM 30 amp controller and all we can figure is she (her alleged mechanic) pulled the batteries off to "clean the terminals" and left PV running. We put a DC circuit breaker on the PV leg so we can disconnect that first if working on the batteries, although in past installs and in my factory GoPower install, the solar just ran straight to the batteries 24/7 and they cam from the factory with no lead on the battery until I picked it up and installed the two GC2's I brought to the PDI.





BUT YES IT IS SIMPLE AS HELL TO ADD A LITTLE SOLAR TO ANY RIG

[Tom48]

Originally Posted by corn18

The run from the panels to the controller will be 14 ft. one way. The kit comes with 10ga wire. Seems that combo would work better with series panels to keep the amperage lower.

for just two panels 10ga will be fine series or parallel. Series will start to charge at the crack of day while parallel will come up a bit later, but in series one panel shaded by a vent or AC and the whole thing is pretty much dead

[Hclarkx]

Originally Posted by Barry Allen

- downside of series: Think of a water hose with 2 taps. If either tap is closed you get no water. IE if one panel is in the shade and the other is in full sun, you output is limited by the one in the shade. In the places we tend to camp, it is almost guaranteed that one side of our trailer is always in the shade.

The ideal layout for an RV (in my opinion) is 4 panels. 2 in series on each side of the roof then the pairs connected in parallel.

My experience is with panels made for RV use. They invariably have bypass diodes that let the current from the sun laden panels bypass the shaded panel(s). Hence with four series panels, one shaded (even partially) and three in the sun, the output should be near 75% of what would result with full sun on all panels. Diodes do insert a bit of voltage drop, so the result is usually closer to 70%. But, that's still quite effective. The OP's Rich panels do have bypass diodes.

[TitanMike]

Originally Posted by Hclarkx

My experience is with panels made for RV use. They invariably have bypass diodes that let the current from the sun laden panels bypass the shaded panel(s). Hence with four series panels, one shaded (even partially) and three in the sun, the output should be near 75% of what would result with full sun on all panels. Diodes do insert a bit of voltage drop, so the result is usually closer to 70%. But, that's still quite effective. The OP's Rich panels do have bypass diodes.

If using Schottky diodes, as most solar panels have, the voltage drop across the diode ranges from .15 to .45 volts compared to regular PnP diodes voltage drop of .6 to 1.7 volt drop.

Voltage drop is negligible overall.

[bbells]

Yep. It is simple. You don't even need to screw the panels on the roof. Roofing tape holds flat panels forever.

[TitanMike]

Originally Posted by bbells

Yep. It is simple. You don't even need to screw the panels on the roof. Roofing tape holds flat panels forever.

Might be an oversimplified statement.

On a solid roof of fiberglass or aluminum tape MIGHT hold the panels.

On a "membrane" roof of EPDM, TPO, or PVC, that's going to depend on how well the membrane itself is attached to the substrate.

Some roofs will billow up like Superman's cape as they go down the road.

How do you tape solar panels to a roof like that??????

[bbells]

Originally Posted by TitanMike

Might be an oversimplified statement.

On a solid roof of fiberglass or aluminum tape MIGHT hold the panels.

On a "membrane" roof of EPDM, TPO, or PVC, that's going to depend on how well the membrane itself is attached to the substrate.

Some roofs will billow up like Superman's cape as they go down the road.

How do you tape solar panels to a roof like that??????

Of the dozens we have taped on roofs we have never found one that good roofing tape does not hold permanently.

[corn18]

I know I am not going to just tape it to my roof. It's rubber and there are spots where it is clearly not securely attached to whatever is under it. It doesn't flop around but I ain't gonna tape a 30 lbs solar sail to it. So I'm going with the included Z brackets and screws. I'll put tape on the Z brackets as well, but I don't trust my roof covering to hold the panels on.

[bbells]

Originally Posted by corn18

I know I am not going to just tape it to my roof. It's rubber and there are spots where it is clearly not securely attached to whatever is under it. It doesn't flop around but I ain't gonna tape a 30 lbs solar sail to it. So I'm going with the included Z brackets and screws. I'll put tape on the Z brackets as well, but I don't trust my roof covering to hold the panels on.

The panels that are taped on are semi flexible flat panels as stated. I don't put hard framed panels on rvs anymore. The screws and plates end up being weak points and vibration sometimes cracks the roofing around the anchor points.

[DavidWJ]

That diagram is wrong, unless there is a charge controller that will work with many different voltages.

Connect the panels in parallel using waterproof "solar" cables and run their output to the charge controller.
Connect the charge controller outputs to the batteries, so they will be charged.
Connect the batteries to the inverter if you have one.

[corn18]

Originally Posted by DavidWJ

That diagram is wrong, unless there is a charge controller that will work with many different voltages.

Connect the panels in parallel using waterproof "solar" cables and run their output to the charge controller.
Connect the charge controller outputs to the batteries, so they will be charged.
Connect the batteries to the inverter if you have one.

Yes there is a charge controller that works with many different voltages. Most of them do. The one I have from Rich solar can do up to 100V on the input side and 32V on the output side. So I could do 4 panels in series feeding the controller. Although I would do a 2S/2P configuration with 4 panels. 2 in series on each side of the roof and then parallel them sets.

[Hclarkx]

Originally Posted by corn18

I know I am not going to just tape it to my roof. It's rubber and there are spots where it is clearly not securely attached to whatever is under it. It doesn't flop around but I ain't gonna tape a 30 lbs solar sail to it. So I'm going with the included Z brackets and screws. I'll put tape on the Z brackets as well, but I don't trust my roof covering to hold the panels on.

I've used self-leveling caulk, eternabond (as a gasket), and butyl rubber in this order in my four solar upgrades. By far the butyl rubber worked the best and was easiest to work with. My roof is not flat so I shaped the lower wing of each z bracket (in a vise) so it was completely flat against the roof. My roof is only 1/4" luan over foam so I was very careful to drill pilot holes and use SS screws to not tear up the luan. I used shorter screws than came with the brackets. I drilled a third hole in each bracket. I used extra brackets on the leading panels that might "catch air".

[Hclarkx]

Originally Posted by corn18

Yes there is a charge controller that works with many different voltages. Most of them do. The one I have from Rich solar can do up to 100V on the input side and 32V on the output side. So I could do 4 panels in series feeding the controller. Although I would do a 2S/2P configuration with 4 panels. 2 in series on each side of the roof and then parallel them sets.

This is a good plan IMHO. Operating voltage will be around 40-44 volts and lower when the MPPT controller pulls voltage down to eke out some extra power. Giving the MPPT controller about 20 volts to work with works well. Also, the MPPT controller will be slightly (about 1%) more efficient with this voltage than with higher voltage (say three panels in series).

If your layout allows a third panel in each of the series strings when upgrade time comes, you will likely get enough extra energy via MPPT action to cover the higher controller losses, but just barely (I'm assuming a controller that can handle the power would be used). My solar controllers are "overpaneled" about 20% to get full use of the controller.

[eric1514]

My roof is fiberglass over plywood. I used 1/4-20 well-nuts. They seal by design but I put a blob of Dicor on each one before I put them in their holes. They hold very tight.

[faithie999]

How far does the body of the well protrude into the roof? I have a 2021 surveyor which has an EPDM membrane over what I assume is plywood.

I'm probably unnecessarily worried about nicking a wire inside the roof while drilling for the well fitting.

Thanks

Ken

[eric1514]

Originally Posted by faithie999

How far does the body of the well protrude into the roof? I have a 2021 surveyor which has an EPDM membrane over what I assume is plywood.

I'm probably unnecessarily worried about nicking a wire inside the roof while drilling for the well fitting.

Thanks

Ken

You can get them in various lengths. I bought mine at Lowes. Here's a link

Lowes Well Nuts


They are 3/4" long to start with. The roofing material and the plywood use up about 3/16" of that so about 9/16" will protrude into the ceiling before you tighten them. I have ducted A/C so I knew I had 3"-4" to play with.

I had to drill 1/2" holes for them and I used a small hole saw, not a twist bit. I used a total of 8. You can see one of them (covered in Dicor) holding down the piece of UniStrut the panels are mounted to.

[faithie999]

Thanks for the quick reply.

I don't have ducted AC so only would need to find out if there are wires below the plywood that I need to be aware of. I will contact a tech at my dealer to see what he says.

Ken