Zamp port and panel wattage

[Adrian Farmer]

I believe that the Zamp port on my 2020 21NE is wired into the charge controller, presumably in parallel with my two 190 W roof mounted panels. Therefore, if I wanted to acquire a portable panel, I assume I would be looking to get a panel that is >=190 W, else a smaller wattage might constrain the output of the roof panels. In practice, however, the use of a smaller wattage portable panel, might not always be a system constraint, because in situations where/when it might be needed, the roof panels might be shaded and not putting out full power.

I refer not to re-connect the Zamp port directly to the batteries and deal with two different controllers (but I could be convinced of the errors in my thinking here). I know there are a lot of comments on this issue on the forum, but I don't see much consistency.

Hence, I would appreciate different views on the best way to proceed.

[rainyescape]

I’ve heard in other places similar concerns about sizing portable panels, and I’ve also heard from people who seem to know what they are saying that it shouldn’t matter or isn’t worth worrying about. Just get the panels you like. I have the same setup as you, and we just tested two Jackery panels (each are 100 W) that don’t have controllers, and they were delivering about 10A as registered on the GoPower solar controller with our 190W roof panel covered, and about 13A with it uncovered. The jackery panels were angled right to the evening sun, and the roof panel was flat and at a bad angle. So that seemed like pretty great performance to me.

I only use the controller-less Jackery panels because they were my father in law’s and unused otherwise with their jackery. I think they were pretty expensive and you’d be fine with any other panel that comes without a controller, especially ones that can handle some rain and are sturdy (sometimes labeled as briefcase panels). I’ve heard good and bad things about the Renogy panels. Recently people were mentioning how great the Harbor Freight panels were since they are so affordable. I think it’s these ones, and 2 of them might be perfect for your set up. Maybe they’ll go on sale again.

https://www.harborfreight.com/100-wa...ase-57991.html

(Edit: I mistakenly said I had 2x 200 W panels, I actually have 2x 100 W panels for a total of 200 W)

[rainyescape]

Oh, and Dustin at ETI says the controller can handle up to 600 W total, so an additional 410 W to your 190 W roof panel.

[Adrian Farmer]

Thanks rainyescape, that the kind of feedback I was hoping for. Nothing like practical experience!

[rainyescape]

I mistakenly said I had 2x 200 W panels, I actually have 2x 100 W panels for a total of 200 W. With the roof panel, a grand total of 390 W. Sorry about that!

[Vermilye]

You do not need to match the wattage of the rooftop panels you are going to parallel them with a portable panel. Ideally, the working voltage of the portable & the rooftop panels should match, but if the panels are off by less than a couple of volts, it won't make a difference, even if both are in full sun.

[alanmalk]

I have sitting around somewhere in the workshop, a 24 volt panel and in the garage, a 18 volt panel, of significantly different wattages. When I somehow manage to get some free time I plan to hook them together and charge a battery. And while doing so, measure the output of each while playing with the connections. My goal is to disprove this notion that it is a "bad thing" to hook 2 different panels together. But until then...

[richm]

Originally Posted by alanmalk

I have sitting around somewhere in the workshop, a 24 volt panel and in the garage, a 18 volt panel, of significantly different wattages. When I somehow manage to get some free time I plan to hook them together and charge a battery. And while doing so, measure the output of each while playing with the connections. My goal is to disprove this notion that it is a "bad thing" to hook 2 different panels together. But until then...

You may already be aware, but for those interested in how it may work... Panels of differing voltages in parallel will produce power, although slightly less than if they each had a separate MPPT controller. The 18V and 24V panels will each have a maximum power point, indicated by the blue dot:


from: https://electricalacademia.com/renew...ing-principle/

An MPPT controller will adjust the panel voltage to the maximum power point of the panel. Using two controllers would allow each panel to operate at its individual maximum power point.

Regardless, putting them in parallel should provide power.

[SRS]

I’m a little confused by the solar wiring in my 2022 17A. Specifically, how a panel connected to the Zamp port interacts with the solar controller. The wiring diagram provided to me by Escape, indicates that both the Zamp port and the roof solar should be connected to the + & - PV side of the controller and this makes sense. However, after tracing the wires from the Zamp port to the controller it appears that they are connected to the WAGO connectors that are spliced to the Battery + & - side of the controller which I find confusing. Mainly I’m wondering how the controller would see a PV on the Zamp port if it’s not going into the PV side of the controller. There is probably something I’m missing so hopefully someone can enlighten me. I have emailed Escape asking the same question.

[Brian B-P]

I agree that the external (Zamp) port should be wired to the PV side of the controller, and must be for the external panel to share the controller with the built-in panels. If the external panel is wired to the battery side of the controller (as it appears to be, physically), the controller doesn't see and cannot control the external panel - the external panel is just another source of voltage, like a shore power converter, which confuses the solar charge controller's idea of the state of charge of the battery.

[SRS]

Originally Posted by Brian B-P

I agree that the external (Zamp) port should be wired to the PV side of the controller, and must be for the external panel to share the controller with the built-in panels. If the external panel is wired to the battery side of the controller (as it appears to be, physically), the controller doesn't see and cannot control the external panel - the external panel is just another source of voltage, like a shore power converter, which confuses the solar charge controller's idea of the state of charge of the battery.

Thanks for the reply. That's exactly what I was wondering and also that without going through the controller it could potentially damage the battery through overcharging. I'll be interested to see what Escape says.

[Brian B-P]

Originally Posted by SRS

... and also that without going through the controller it could potentially damage the battery through overcharging.

Yes, without a controller external to the trailer, the external panel would be unregulated and could eventually over-charge the battery.

[SRS]

Originally Posted by Brian B-P

Yes, without a controller external to the trailer, the external panel would be unregulated and could eventually over-charge the battery.

This might explain why I don't see any change in out on the Victron app when I connect the suitcase.


It would appear I may have to do some rewiring or add another controller. Had I known this, I would have gotten a solar suitcase with a controller. Maybe I could add one to the to the suitcase.

[Perry Butler]

Originally Posted by SRS

It would appear I may have to do some rewiring or add another controller. Had I known this, I would have gotten a solar suitcase with a controller. Maybe I could add one to the to the suitcase.

You'll lose power buy adding one to the suitcase and then through the Zamp port. You want as high a voltage going to the Zamp port as possible and want the controller as close to the battery as possible.

We hook our rooftop to a Victron 100/30 and our Renogy suitcase to a Victron 100/20 controller. Both controllers are hooked separatly to the battery. You could put your second controller right next to the first, or somewhere else close to the battery.

Enjoy,

Perry