Add Portable Solar to Existing Solar

[Peterk56]

We have a Jayco 212qrb baha rocky mountain edition TT that came equipped with 270 Watts of solar panels on the roof. I want to add 100-200 watt portable (suitcase) solar panel(s) to our system for times when we're parked in partial shade, or cloudy days.

Do I need a controller with the suitcase panels, or can I plug them directly into our existing onboard controller?

[Skibane]

Depends on how much unused power-handling capacity your present controller has.

If it's rated for 800 watts - and you're adding 200 watts of portable panels to your existing 270 watts of panels, that's 470 watts - which is well below the rated capacity of your controller.

OTOH, if your controller is only rated for 300 watts, you're pretty much tapped out on it already - even before you add any portable panels.

One other consideration is that different brands and models of solar panels don't always produce their full output when connected in parallel with each other. Putting them on separate charge controllers tends to avoid this.

[Marine359]

If your roof mount is wired directly to the battery thru a controller, you can’t wire up a portable to that controller without a combiner box. It’s much easier if the portable panel connects to its own controller. You can buy a panel with built-in pwm controller. This will severely limit the distance you can place it away from the battery due to voltage drop. Or, you can mount a mppt controller near the battery. This way gives you the ability to place the panel 30 ft away, using 10awg cable with virtually no voltage drop. The cable should connect to a sidewall SAE port, and from there should be in-line fused to the controller.

I’m using a 120w soft folding panel thru a SAE sidewall port to 75/15 controller, then to fuse block, then to battery. The controller mounted 3 ft from battery. It’s worked greAt at getting the maximum charge amperage from panel to battery.

[vsheetz]

PV arrays with differing configuration, specs, or physical orientation should be on a separate controller.

[pvcampbell]

Originally Posted by vsheetz

PV arrays with differing configuration, specs, or physical orientation should be on a separate controller.

This is the best advice. The voltage outputs and other specs from the two solar arrays will be different, so your solar controllers must be separate. I used the same dual-array arrangement for a while on my old coach, so I had a Victron controller for the main roof-top panels, then added a cheaper used (eBay purchase) controller sized for my portable panels. I made short pigtails with solar cable pugs connected to the controller for the portable panels and extended them outside when in use, then made 50' extension cables to run to the portable panels. In the attached, you can see the two controllers. Separate solar inputs, but the outputs are combined.

I would avoid the portable setups that have the controller(s) mounted to the back of the solar panels. Those are fine if the panels are within a few feet of your bateries, but for a longer run to find sun away from your RV, you are better off running the higher solar panel voltage (usually around 19V) through the longer cable run, and have the controller closer to the batteries.

[Mark_K5LXP]

Originally Posted by Marine359

you can mount a mppt controller near the battery. This way gives you the ability to place the panel 30 ft away, using 10awg cable with virtually no voltage drop.

You still get voltage drop and lost power, albeit a bit less at panel voltage. The big difference is keeping the voltage to the batteries within regulation.

Mark B.
Albuquerque, NM

[Marine359]

Originally Posted by Mark_K5LXP

You still get voltage drop and lost power, albeit a bit less at panel voltage. The big difference is keeping the voltage to the batteries within regulation.

Mark B.
Albuquerque, NM

I’ve measured VOC at the panel and at the end of my 30ft 10awg cable and voltage drop was about 1/2 a volt. I consider that negligible. Of course it’s very important you have an efficient mppt controller to max out the charge current. You can’t do that with a big voltage drop, and you can’t do it with PWM. If you put a panel with pwm 30ft away, you’ll be sending higher amperage. The trick is to send voltage down the wire as high as possible, as voltage drop is far less at lower amperage.

[Peterk56]

Originally Posted by Marine359

If your roof mount is wired directly to the battery thru a controller, you can’t wire up a portable to that controller without a combiner box. It’s much easier if the portable panel connects to its own controller. You can buy a panel with built-in pwm controller. This will severely limit the distance you can place it away from the battery due to voltage drop. Or, you can mount a mppt controller near the battery. This way gives you the ability to place the panel 30 ft away, using 10awg cable with virtually no voltage drop. The cable should connect to a sidewall SAE port, and from there should be in-line fused to the controller.

I’m using a 120w soft folding panel thru a SAE sidewall port to 75/15 controller, then to fuse block, then to battery. The controller mounted 3 ft from battery. It’s worked greAt at getting the maximum charge amperage from panel to battery.

Thanks so much, it sounds like this is the way to go: How do I find out how to buy/install a separate SAE port? Or might my trailer already have one? I have seen portable panels that offer separate controllers: it sounds like i want a mppt, as i want to be able to have the panels in the sun when the rv is not. I'm not sure what you mean by "in line fuse it to the controller". Is there YouTube channel that shows people how to do this? Or a specific vendor that will explain it? I'm pretty handy, but need some guidance.

[Peterk56]

Originally Posted by pvcampbell

This is the best advice. The voltage outputs and other specs from the two solar arrays will be different, so your solar controllers must be separate. I used the same dual-array arrangement for a while on my old coach, so I had a Victron controller for the main roof-top panels, then added a cheaper used (eBay purchase) controller sized for my portable panels. I made short pigtails with solar cable pugs connected to the controller for the portable panels and extended them outside when in use, then made 50' extension cables to run to the portable panels. In the attached, you can see the two controllers. Separate solar inputs, but the outputs are combined.

I would avoid the portable setups that have the controller(s) mounted to the back of the solar panels. Those are fine if the panels are within a few feet of your bateries, but for a longer run to find sun away from your RV, you are better off running the higher solar panel voltage (usually around 19V) through the longer cable run, and have the controller closer to the batteries.

Hey, Thanks for that description and the picture. My installed solar controller is on the wall, so I'll have to figure out how it's connected to the batteries or where the output wires are. And how to combine the output wires? Just splice together the output wires? I'll take a look at your pic later on a large monitor to see if i can figure it out.

[Marine359]

Originally Posted by Peterk56

Thanks so much, it sounds like this is the way to go: How do I find out how to buy/install a separate SAE port? Or might my trailer already have one? I have seen portable panels that offer separate controllers: it sounds like i want a mppt, as i want to be able to have the panels in the sun when the rv is not. I'm not sure what you mean by "in line fuse it to the controller". Is there YouTube channel that shows people how to do this? Or a specific vendor that will explain it? I'm pretty handy, but need some guidance.

SAE sidewall port on Amazon for less than $20. It does not have very long wires on the inside, so if you don’t connect to your charge controller within 2ft on the inside, you’ll have to splice a longer set of wires. To install drill a hole in the sidewall out of the way of the pass thru door, but high enough to route the wires across the ceiling of the pass thru. I routed my wires from the charge controller to a fuse block to protect the wire from controller to battery. If you’re using 10awg wire from the SAE port to the controller, it’s really not necessary to fuse that part of the wiring IMHO.

The first picture is how the charge controller looks inside the pass thru. Second picture shows the SAE port on the outside.

[pvcampbell]

The 12v outputs from the solar controllers need to end up at the battery bank to charge the batteries. Whether they are connected together closer to the controllers and then one cable goes to the batteries, or each controller is wired directly to the battery bank doesn't matter - all the power is going to the same place. You just want the controller for the portable panels to be as close to the battery bank as possible to minimize the size of cabling required. Most smaller controllers will only accept 8 gauge or smaller cable.

For connecting the cables, I made custom sizes as needed using readily available solar connectors like these. If you go to Amazon and search on "solar cable connectors", you will find a multitude of options, including pre-made cables in any length. As I said above, I didn't need any through-wall connection, as I just ran a short cable length from the controller to the outside, where I plugged in my extension cables to the panels when in use. My basement compartment door closed over the cables without a problem, but then, I'm in a motorhome.

[Peterk56]

Originally Posted by Marine359

SAE sidewall port on Amazon for less than $20. It does not have very long wires on the inside, so if you don’t connect to your charge controller within 2ft on the inside, you’ll have to splice a longer set of wires. To install drill a hole in the sidewall out of the way of the pass thru door, but high enough to route the wires across the ceiling of the pass thru. I routed my wires from the charge controller to a fuse block to protect the wire from controller to battery. If you’re using 10awg wire from the SAE port to the controller, it’s really not necessary to fuse that part of the wiring IMHO.

The first picture is how the charge controller looks inside the pass thru. Second picture shows the SAE port on the outside.

@pvcampbell @Marine359 Thanks to both of you: Now this is starting to make sense. SAE port looks doable. I can get the new controller in the pass-thru, which of course is close to the batteries (2X Lead Acid cheapos up front on the tongue).

But, the OEM installed controller is in the wall and I can't see any of the wiring. See attached Photo: these the only exposed wires I see. They're right at the front of the rig between the front wall and the batteries. Not sure why there are three junction points here.

Do I just patch the new controller output wires into the left and right junction points outside? And how to get them through the front wall: maybe I can find where the other wires are coming through the wall and squeeze the two new wires through?

[Peterk56]

Thanks everyone for your replies and advice and pictures! I just ordered a 100W Renogy portable suitcase, and Rich 20Amp MPPT controller, and 30 and 20 ft cables to allow for up to 50ft reach. For now, I don't expect to use it much, so I won't permanently mount the controller or patch in the wires to the battery. I'll just connect wires from the controller directly to the battery terminals on the occasions I need it. If that turns out to be more than I think, I'll pay someone to figure out/find the hidden wiring on my TT and patch the wires in. I can see the hot wire feeding the battery, but the negative wire coming from the TT seems to be buried inside the front wall or underneath. I just don't feel comfortable taking it apart on my own.