Adding portable solar to roof mounted panel

[LarryandLiz]

Adding portable solar to roof mounted panel

I have a roof mounted 160 Go-power solar panel and recently purchased a Portable 130 Watt Go-power solar panel The roof mounted panel has its’ ETI installed inside the trailer controller while the Portable 130 Go_power panel has its' controller. Does that give me a total of 290 to feed my two deep cycle 6 volt batteries?

I’ve always assumed I’d be using 290 when estimating my daily amp draw.

The reason I ask is that I was told by a RV tech person that since the panels weren’t matched (in size 160 / 130) that I will be somehow limited (because of the controllers?). The tech person say's their company always adds the same size of portable panel to the mounted panel.

Does that make sense ?

[Effie]

Excuse my French but what this “tech” told you is BS. There is no need for these two panels each with its own charge controller to be identical. You will have 290w of solar panels when using them both, keep in mind that in real life you will very rarely get anything above 80% of the 290w because conditions are never optimal. I do suggest configuring both controllers with the same charging parameters.

[LarryandLiz]

Thanks Effie. I’ll look into controllers and parameters

[LarryandLiz]

I found this helpful “solar calculator” on GoPower’s website for calculating amp draw

https://gpelectric.com/calculator/

[TTMartin]

Originally Posted by Effie

Excuse my French but what this “tech” told you is BS. There is no need for these two panels each with its own charge controller to be identical. You will have 290w of solar panels when using them both, keep in mind that in real life you will very rarely get anything above 80% of the 290w because conditions are never optimal. I do suggest configuring both controllers with the same charging parameters.

I agree, if the two panels were both using the same charge controller what the tech said would be correct. Since each panel has it's own charge controller each panel is outputting independent of the other panel and they have no relation to each other.

[Brian B-P]

Originally Posted by LarryandLiz

I have a roof mounted 160 Go-power solar panel and recently purchased a Portable 130 Watt Go-power solar panel The roof mounted panel has its’ ETI installed inside the trailer controller while the Portable 130 Go_power panel has its' controller. Does that give me a total of 290 to feed my two deep cycle 6 volt batteries?

Yes.

Originally Posted by LarryandLiz

The reason I ask is that I was told by a RV tech person that since the panels weren’t matched (in size 160 / 130) that I will be somehow limited (because of the controllers?). The tech person say's their company always adds the same size of portable panel to the mounted panel.

Does that make sense ?

No, it doesn't make sense. If the two panels (160 W and 130 W ratings) have the same characteristic voltages (e.g. voltage at maximum power), and they are in the same sun exposure conditions, the larger one will just contribute about 23% more current than the smaller one.

Originally Posted by Effie

Excuse my French but what this “tech” told you is BS. There is no need for these two panels each with its own charge controller to be identical. You will have 290w of solar panels when using them both, keep in mind that in real life you will very rarely get anything above 80% of the 290w because conditions are never optimal. I do suggest configuring both controllers with the same charging parameters.

True!

Originally Posted by TTMartin

I agree, if the two panels were both using the same charge controller what the tech said would be correct.

No, even when connected in parallel to the same controller there is no need for the panels to be identical or even close in power rating - they only need to match in characteristic voltage.

Originally Posted by TTMartin

Since each panel has it's own charge controller each panel is outputting independent of the other panel and they have no relation to each other.

That's true, although as Effie noted the controllers should agree on their behaviour for optimal operation.

[IanC]

Does anyone know what the "characteristic voltage" is for the ETI installed solar panels? I've read numerous times that characteristic voltage needs to match on both rooftop and portable solar panels, but don't know how to establish that. I have a GoPower suitcase panel which I believe is advertised as 12-volt. Not sure if that is the actual output, or just that it means is suitable for a 12 volt system. As I understand it, a charging device needs to run at a higher voltage to properly charge battery.

[rubicon327]

Originally Posted by IanC

Does anyone know what the "characteristic voltage" is for the ETI installed solar panels? I've read numerous times that characteristic voltage needs to match on both rooftop and portable solar panels, but don't know how to establish that. I have a GoPower suitcase panel which I believe is advertised as 12-volt. Not sure if that is the actual output, or just that it means is suitable for a 12 volt system. As I understand it, a charging device needs to run at a higher voltage to properly charge battery.

Might want to double check with ETI but the Overlander 190W panel should be what is installed when opting for solar. Specs are here:
https://s3-us-west-2.amazonaws.com/c...ER-RETREAT.pdf

[Brian B-P]

Originally Posted by IanC

I have a GoPower suitcase panel which I believe is advertised as 12-volt. Not sure if that is the actual output, or just that it means is suitable for a 12 volt system. As I understand it, a charging device needs to run at a higher voltage to properly charge battery.

It means suitable for a nominally 12 volt system. The voltage at peak power in full sun will be very roughly 18 volts. 18 volts would be too high for a "12 volt" battery, but the actual voltage will depend on operating conditions, and the controller will regulate the voltage actually applied to the battery.

[IanC]

Originally Posted by rubicon327

Might want to double check with ETI but the Overlander 190W panel should be what is installed when opting for solar. Specs are here:
https://s3-us-west-2.amazonaws.com/c...ER-RETREAT.pdf

Thanks for that link rubicon327. It appears the output voltage of the rooftop panel and my portable panel both match at about 19 volts. Perfect.

[Perry Butler]

Originally Posted by IanC

Thanks for that link rubicon327. It appears the output voltage of the rooftop panel and my portable panel both match at about 19 volts. Perfect.

Contrary to what some sites say, they don't have to match up perfectly. We have the 170 watt ETI supplied GoPower panel that came with our 2018 5.0. The voltage (VMP) is 19.3 and the current (IMP) is 8.8. Looks like I'll be adding two 100 watt Renogy Eclipse panels to the front of our 5.0 that have voltage (VMP at 17.7) and current (IMP) at 5.7. In theory we'll have 170 +100 +100 watts or 270 total.

We'll be connecting them in parallel to avoid shading in heavy cover in Minnesota State Parks. In parallel the panels run at the lowest voltage of the three or 17.7 with our 5.0. That trio of panels will yield from 354-358 watts depending on whose math and loss you gather the data from. That 354 is about a 4% loss, but rather meaningless in the total scope of things.

Those of us who don't want to put an identical 170 watt panel on the front will have trouble finding a panel to match the voltage just for perfection. I'll be more than happy to have 354 watts on the roof that can have a couple of panels shaded.

Mowgli Adventures has a neat table near the bottom of the page to enter your data and give you your expected output. Or you can do the math given by Nate Yarbrough - Explorist Life.

youtube.com/watch?v=jejro4zkl8I&t=2s&ab_channel=EXPLORISTlife-DIYCampers

Again, you don't need to be perfect.

Since purchasing our 5.0, because of shading, in some parks we had nearly zero output from our 170 watt panel and had to take the portable out to get enough to recharge our batteries. In many parks all we needed was to have a panel up front where there was no shading, but didn't, so out came the portable. While I don't regret getting the 100 watt portable, I find a portable a PITA, but when you need one it's worth the effort. There will be times all three of our panels will be shaded and a portable needed.

Enjoy,

Perry

[Perry Butler]

Originally Posted by Perryb67

Contrary to what some sites say, they don't have to match up perfectly. We have the 170 watt ETI supplied GoPower panel that came with our 2018 5.0. The voltage (VMP) is 19.3 and the current (IMP) is 8.8. Looks like I'll be adding two 100 watt Renogy Eclipse panels to the front of our 5.0 that have voltage (VMP at 17.7) and current (IMP) at 5.7. In theory we'll have 170 +100 +100 watts or 270 total.

Sorry about the math!

It should have been written, "In theory we'll have 170 +100 +100 watts or 370 total," not 270 total.

Enjoy,

Perry

[Melusine]

I have two rooftop panels which, I've been assuming, will be sufficient for our needs. However, the idea of having a portable panel as supplement occasionally is appealing. We do have the Zamp panel connection, so here's the question: is there a "plug and play" portable panel which will be totally compatible with the installed system?
Thanks!
Jen & Jon in AZ

[Vermilye]

Most portable panels come with a controller, however they can be ordered without one. An example is this Renogy 100 watt portable. Unfortunately, it comes with MC4 connectors, so you would need an adapter that goes from MC4 to SAE (the type connector Escape installs for portable panels).

One last point - check the polarity of both the panel SAE connector & the Trailer's SAE connector to be sure the polarity is the same. The solar industry has not decided on a standard. A reversing adapter is available if you don't want to switch Escape's wiring (if necessary).

[Perry Butler]

Originally Posted by Vermilye

Most portable panels come with a controller, however they can be ordered without one. An example is this Renogy 100 watt portable. Unfortunately, it comes with MC4 connectors, so you would need an adapter that goes from MC4 to SAE (the type connector Escape installs for portable panels).

When we ordered our Renogy 100 watt panel we also ordered the panel with SAE connectors. Rather than needing to remember to always use a SAE polarity adapter we simply reversed the wires to the camper's controller. Of course I still checked the polarity with a multimeter before hooking up.

Enjoy,

Perry

[MBA80]

Originally Posted by LarryandLiz

Adding portable solar to roof mounted panel

I have a roof mounted 160 Go-power solar panel and recently purchased a Portable 130 Watt Go-power solar panel The roof mounted panel has its’ ETI installed inside the trailer controller while the Portable 130 Go_power panel has its' controller. Does that give me a total of 290 to feed my two deep cycle 6 volt batteries?

I’ve always assumed I’d be using 290 when estimating my daily amp draw.

The reason I ask is that I was told by a RV tech person that since the panels weren’t matched (in size 160 / 130) that I will be somehow limited (because of the controllers?). The tech person say's their company always adds the same size of portable panel to the mounted panel.

Does that make sense ?

No it doesn’t make sense. Two charge controllers trying to do the same job will cause conflicts. Yes, you add the wattage and the panels can be different wattages.

[Perry Butler]

Originally Posted by MBA80

No it doesn’t make sense. Two charge controllers trying to do the same job will cause conflicts. Yes, you add the wattage and the panels can be different wattages.

Yes, it does make sense. You have have two charge controllers feeding the same battery bank. It's done all the time.

You can't have one controller feeding another controller, but that's just bad electrical knowledge. Again, you can have two controllers feeding the same battery bank.

Enjoy,

Perry

[Small but Sweet]

Originally Posted by Perryb67

Sorry about the math!

It should have been written, "In theory we'll have 170 +100 +100 watts or 370 total," not 270 total.

Enjoy,

Perry

There I was thinking this was some funny electrical way of wattage adding up differently. Like two parallel things in series with the third thing, haha.