Community Forums

Jerry Burks · 04-23-2021, 04:33 PM

My new 5th wheel came with one 190W Go-Power panel installed.
I replaced already the simple PWM controller with a 40 amp Renogy Rover MPPT controller. Now I want to install a second solar panel. I opted for another identical Go-Power to avoid potential balance issues.

Normally I would configure them in series go get better output in low light conditions and reduce voltage drop in the cable. But the Go-Power manual specifically warns to install multiple panels in parallel (quote "Failure to follow this connection procedure will cause the system to produce large currents which the protection device, DC fuse is not designed the handle" end quote).

Now I thought that all modern solar panels have proper parallel and serial diodes to prevent damage to the panel but then, maybe this one not? Does not make sense because the panel is already more expensive than the typical panels on Amazon.

Any opinion? Maybe not take a risk and just do what the doctor said?

Thanks, JB

iluvuk · 04-25-2021, 08:51 PM

i'm not sure I understand your post clearly or the instructions you quoted. Wiring the panels in parallel will double the current and keep the voltage the same so if there is a worry about overcurrent, parallel should be avoided.

As you apparently know, there are valid reasons to avoid series wiring because shading one panel will bring down the entire series string to a lower output. Parallel helps reduce this problem a bit but will double the current so you need to have the charge controller and wire gauge to handle the extra current.

Jerry Burks · 04-26-2021, 12:21 PM

Quote:

Originally Posted by iluvuk

i'm not sure I understand your post clearly....

Well, that is the point. I quoted the warning in the Go-Power manual and I don't understand it, either.

I have the additional panel installed now and to be sure connected both in parallel. I estimate about 0.9 V voltage drop at 18 amps in 50 feet total of 10 gage wire. That would be 5% loss of the panel voltage vs. 2.5% when in series. Part of that difference should be compensated for by about 1% better efficiency of the Renogy Rover MPPT controller running at 20V compared to 40V.

So I guess I can live with that...

Jerry Burks · 04-26-2021, 09:24 PM

Oh well. After I did the install I got feedback from Go-Power tech support:

"Thank you for your inquiry.

We usually use pwm controllers with our 190 watt panels. so this is why we suggest wiring in parallel. (the limitation on the controller) With a MPPT controller it should be able to handle a higher voltage and be able to be wired in series . I would check the max voltage and current input on the controller to verify this."

So the warning was not about the panels but rather the PWM controller....

Anyway, I will just leave it wired parallel for now. Small difference.

radar · 04-26-2021, 09:32 PM

Quote:

Originally Posted by Jerry Burks

Oh well. After I did the install I got feedback from Go-Power tech support:

"Thank you for your inquiry.

We usually use pwm controllers with our 190 watt panels. so this is why we suggest wiring in parallel. (the limitation on the controller) With a MPPT controller it should be able to handle a higher voltage and be able to be wired in series . I would check the max voltage and current input on the controller to verify this."

So the warning was not about the panels but rather the PWM controller....

Anyway, I will just leave it wired parallel for now. Small difference.

Actually I think you know this stuff better than many of us. Sounds like it turned out well.

SJ-Chris · 04-29-2021, 03:27 PM

Quote:

Originally Posted by Jerry Burks

Well, that is the point. I quoted the warning in the Go-Power manual and I don't understand it, either.

I have the additional panel installed now and to be sure connected both in parallel. I estimate about 0.9 V voltage drop at 18 amps in 50 feet total of 10 gage wire. That would be 5% loss of the panel voltage vs. 2.5% when in series. Part of that difference should be compensated for by about 1% better efficiency of the Renogy Rover MPPT controller running at 20V compared to 40V.

So I guess I can live with that...

Extra 2.5% (PEAK) drop on your 380w system translates to just 9.5w loss. Drink a beer and enjoy your solar!

treeoflib · 04-30-2021, 09:23 AM

It's a little moot at this point, but you need a certain amount of voltage to charge the batteries and wiring in series gives the MPPT controller more to work with in marginal conditions, like first and last light or cloudy conditions. I noticed the difference when I rewired my four panels from parallel to series/parallel, doubling the voltage.

iluvuk · 04-30-2021, 10:22 AM

Quote:

Originally Posted by treeoflib

It's a little moot at this point, but you need a certain amount of voltage to charge the batteries and wiring in series gives the MPPT controller more to work with in marginal conditions, like first and last light or cloudy conditions. I noticed the difference when I rewired my four panels from parallel to series/parallel, doubling the voltage.

Excellent point!

twinboat · 04-30-2021, 10:47 AM

More amps cause more voltage drop in same size wire.
2 panels and a MPPT controller, run them in series.

iluvuk · 04-30-2021, 12:47 PM

Twinboat is correct. I have noted however that if you have panels in series, even with mppt, and one portion of one panel is shaded, it takes down the output of the entire series string of panels. Tests on youtube seem to confirm this. Have you found a way around this with new technology or other suggestions? Only thing I have found is avoid shade on all panels which is not practical, wire in parallel with bigger wire, or put each panel on its own charge controller. Interested in the experience of others.