Dumb Solar Questions

[BeerBrewer]

We own a 2023 Imagine 2670MK with the factory solar package. We've got a 165W Furrion solar panel on the roof and 25A Furrion MPPT controller. Frankly this seems like a very odd set up. Why did GD put together this arrangement? Since the controller can only handle 25 amps and 300 watts, I'm wondering why they didn't go with a 100 or 150 watt panel and instead went with a crazy expensive 165 watt panel and we can't add a second. Had they gone with 100, 150 or 200 watt panel (which are a lot cheaper) we would have been able to easily upgrade it without exceeding the capacity of the controller. Just seems odd, but I'm no expert.

After reading the controller manual it seems like I can only add another panel in series only. Is that the case? Adding another 165 watt Furrion panel seems out of the question due to it high cost and it exceeds the capacity of the controller by 30 watts (165 x 2 = 330 - 300 = 30). Can I add a random 150 watt panel to it? If so, how would that work? I'd like to beef up the solar capacity if possible.

Am I better off just ripping out the Furrion 25 amp controller and replacing it with another larger one, possibly another brand? Is the 165 watt solar panel worth keeping or should I remove it too and sell it on Ebay?

Thanks!

[Country Campers]

You could add another panel of really any size, the smaller panel will set the tone for power supplied. Adding a 200 watt panel the system will only provide 165 watts, the size of the smaller panel. If you think you could sell the 165 panel then I would do that, being as you want to upsize the system. If you want to just add another panel find one with the closest to the same numbers as the 165 panel, specs for that panel should be on the underside, this will get you the most out of both panels. Depending on how much solar you want would determine the route you should take, including upping the solar controller size.

As far as "why GD would put this size panel on this camper?", your guess is as good as any. My opinion is they size the panel to the size of the 12 v dc fridge, up to 10 cu ft gets this size panel, up to 20 cu ft gets another size, just a guess though.

This is not a "dumb" question, GD's use of solar is quite questionable.

Brian

[TucsonJim]

You don't need to dump your current configuration. I you can get another line from the roof, you could add another string of what ever size you want and then size the controller for the new string. The 165 watt panel and its controller would play nicely with a new panel(s) and another controller.

Jim

[BeerBrewer]

So if I understand this correctly, if I add a second 200 watt panel and connect it in series with the existing 165 watt, that I'll have 365 watts of panels, but the controller will limit to power to only 300 watts. When in full sun, what happens to the power that the extra 65 watts of panel generate? Also can I assume that the 65 watts of extra panel space would help out on cloudy days or when partially shaded? This would fully utilize the exting solar equipment. Then I could do as TucsonJim suggested and just install another separate solar system.

[TedS]

Series or parallel watts are watts. Voltage and current will be different.

[BeerBrewer]

Series or parallel watts are watts. Voltage and current will be different.

I only stated "in series" because I thought I read that an additional panel had to be connected in series in the manual for the solar controller. So I can add any panel to the existing? I read somewhere someone discussing using panels that "match".

[acoleman43]

I only stated "in series" because I thought I read that an additional panel had to be connected in series in the manual for the solar controller. So I can add any panel to the existing? I read somewhere someone discussing using panels that "match".

If you connect panels in series, the voltage of each panel will be combined but the current will be the lowest of the connected panels.

If you connect panels in parallel, the voltage will be the lowest voltage of the connected panels and the current of each panel will be combined.

Either way you will not get full performance from the "larger" panel. But you will get more performance than just one panel.

[Cate&Rob]

The advice to connect panels in series is probably intended as a way to use the existing wiring. As noted earlier, with panels in series the voltage increases but the current will remain more-or-less the same. Connecting panels in parallel will increase the current, likely requiring more or larger gauge wiring from the roof to the controller(s).

Rob

[TucsonJim]

This video from Nate at Explorist Life is the best I've seen on how installing mismatched panels affects charging. BTW, his YouTube channel is one of the best solar resources out there.

https://youtu.be/jejro4zkl8I?si=uVrz402U7Hpd78bt

Jim

[BeerBrewer]

If you connect panels in series, the voltage of each panel will be combined but the current will be the lowest of the connected panels.

If you connect panels in parallel, the voltage will be the lowest voltage of the connected panels and the current of each panel will be combined.

Either way you will not get full performance from the "larger" panel. But you will get more performance than just one panel.

Lets see if I understand you correctly. Lets say I add a Rich Solar 200 Watt solar panel to my existing Furrion 165 solar panel.

Below are the specs for each.

	Furrion 165	Rich Solar 200W
Maximum power (Pmax)	165W	200W
Max Power Voltage (Vmp)	19.4V	20.4V
Max Power Current (Imp)	8.5A	9.8A
Open Circuit Voltage (Voc)	23.83V	24.3
Maximum PV open circuit voltage (Voc)	23.83	24.3V

So lets say I connect them in series. I'd add the voltage two together for the two panels (19.4 + 20.4 = 39.8 Volts) and the amperage would be limited to 8.5A (from the Furrion) and the power would be 39.8v x 8.5A = 338.3W. Which would exceed the max 300W wattage of the controller, so 38.3 wats would be lost. Is that correct?

If I connect the two in series I'd add their amperage together for the two panels (8.5A + 9.8A = 18.3 Amps) and the max voltage would be limited to 19.4V (for the Furrion). So the power would be 19.4V x 18.3A = 355.02 Watts. Again like above I'd be wasting 55.02 watts because we exceeded the 300 watt threshold. Correct?

If I have this correct, my limiting item is my controller in both scenarios. I'm not sure which way is best, but I'd probably go with the series method, so I keep the amperage down. I am assuming that the Furrion solar controller can handle the 39.8 volts. The specs for the controller state that the Maximum PV open circuit voltage (Voc) for the panel is 70.0 Volts and the total for both cells is 48.13 Volts (23.83v + 24.3v = 48.13v).

Thoughts??

TucsonJim, that was a very interesting video! I've seen a few of his videos, but I missed that one.

Lastly I really appreciate everyone's input. I'm in the process of planning/figuring out how to do an electrical upgrade to our trailer, that includes adding two lithium batteries, relocating the the converter, adding a small inverter and finally a solar add.

Thanks!

[acoleman43]

Lets see if I understand you correctly. Lets say I add a Rich Solar 200 Watt solar panel to my existing Furrion 165 solar panel.

Below are the specs for each.

	Furrion 165	Rich Solar 200W
Maximum power (Pmax)	165W	200W
Max Power Voltage (Vmp)	19.4V	20.4V
Max Power Current (Imp)	8.5A	9.8A
Open Circuit Voltage (Voc)	23.83V	24.3
Maximum PV open circuit voltage (Voc)	23.83	24.3V

So lets say I connect them in series. I'd add the voltage two together for the two panels (19.4 + 20.4 = 39.8 Volts) and the amperage would be limited to 8.5A (from the Furrion) and the power would be 39.8v x 8.5A = 338.3W. Which would exceed the max 300W wattage of the controller, so 38.3 wats would be lost. Is that correct?

If I connect the two in series I'd add their amperage together for the two panels (8.5A + 9.8A = 18.3 Amps) and the max voltage would be limited to 19.4V (for the Furrion). So the power would be 19.4V x 18.3A = 355.02 Watts. Again like above I'd be wasting 55.02 watts because we exceeded the 300 watt threshold. Correct?

If I have this correct, my limiting item is my controller in both scenarios. I'm not sure which way is best, but I'd probably go with the series method, so I keep the amperage down. I am assuming that the Furrion solar controller can handle the 39.8 volts. The specs for the controller state that the Maximum PV open circuit voltage (Voc) for the panel is 70.0 Volts and the total for both cells is 48.13 Volts (23.83v + 24.3v = 48.13v).

Thoughts??

TucsonJim, that was a very interesting video! I've seen a few of his videos, but I missed that one.

Lastly I really appreciate everyone's input. I'm in the process of planning/figuring out how to do an electrical upgrade to our trailer, that includes adding two lithium batteries, relocating the the converter, adding a small inverter and finally a solar add.

Thanks!

Yes, I think you got it.

If you are planning to upgrade your solar charge controller, I would do it now. That would eliminate that weak spot in your system. Size for what you want your system to be i the future. I subscribe to the thought that bigger is always better. I'd rather have a solar charge controller specified for more wattage than I use than less wattage.

[TucsonJim]

BeerBrewer - It's not likely that you'll actually lose the 38.3 watts. The reason is that it's rare to achieve 100% charge efficiency. I'd certainly go with a series connection to maximize voltage loss in the 10AWG solar wire from the roof to the controller.

Jim

[BeerBrewer]

BeerBrewer - It's not likely that you'll actually lose the 38.3 watts. The reason is that it's rare to achieve 100% charge efficiency. I'd certainly go with a series connection to maximize voltage loss in the 10AWG solar wire from the roof to the controller.

Jim

I was wondering about the efficiency. Does the fact that the 2 panels totaling 365 watts together have more surface area than 300 watt of panels have anything to do with that?

I thought about upgrading the controller and going with a larger one. Its a lot simpler and cheaper now, to just add another panel to what's there. I like the idea of utilizing what I've got to the max that it can be. Then at a later date I'll buy another controller and run the two solar systems.

[howson]

I was wondering about the efficiency. Does the fact that the 2 panels totaling 365 watts together have more surface area than 300 watt of panels have anything to do with that?

I thought about upgrading the controller and going with a larger one. Its a lot simpler and cheaper now, to just add another panel to what's there. I like the idea of utilizing what I've got to the max that it can be. Then at a later date I'll buy another controller and run the two solar systems.

Maybe, but not the most significant factor. Angle of the panels in relation to the sun, temperature, shading (clouds, etc) all have an impact. The most I've seen from my 1200W setup is just over 1100W, and that's rare.

The significant number you don't want to exceed is the Furrion's 70V Max PV Open Circuit Voltage (VOC). I believe the setup outlined in this thread (with the two panels in series) will work fine to maximize the OEM equipment.