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Old 12-04-2021, 06:59 PM   #1
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Solar; Series, Parallel or both?

Just got a 2022 Wolf Pup 17jgbl. (well August)
Currently upgrading the solar system as running the generator twice a day is a bit much to keep the fridge alive!
Two questions,
1: I just placed the solar panels on the roof, two on the right side, two on the left. Since the roof of the RV has a slight bow to it, the panels are tilted slightly away from each other. I would say a 5-6 degree difference.
I am just starting to get into the electrical science behind all this, but it seems the panels are really only as good as the weakest panel when wired in series (at least with shading issues). Is that true with angles as well?
Should I wire all four in series?
Should wire them all in Parallel?
Should I wire each side in series, then parallel the sides together? I have the ability to do any configuration with my equipment.
2: What should I do with the stock 50W panel and controller? I was planning to just leave as is, but I also upgraded to Lithium. Since the controller is not able to change selections wont the old controller just be worthlessly charging to only 13.6 volts? Can I wire that panel into my new controller? Should I upgrade that controller?
Thanks for all the help!
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Old 12-04-2021, 07:30 PM   #2
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Welcome to the forum its a great place to get your questions answered. We have some real experts on the forum when it comes to solar (I'm not one of them) I"m sure someone will chime in soon. Myself I went with a solar suit case so I could park my rig in the shade and put the solar in the sun. good luck
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Old 12-04-2021, 07:40 PM   #3
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Quote:
Originally Posted by Carbon View Post
Just got a 2022 Wolf Pup 17jgbl. (well August)
Currently upgrading the solar system as running the generator twice a day is a bit much to keep the fridge alive!
Two questions,
1: I just placed the solar panels on the roof, two on the right side, two on the left. Since the roof of the RV has a slight bow to it, the panels are tilted slightly away from each other. I would say a 5-6 degree difference.
I am just starting to get into the electrical science behind all this, but it seems the panels are really only as good as the weakest panel when wired in series (at least with shading issues). Is that true with angles as well?
Should I wire all four in series?
Should wire them all in Parallel?
Should I wire each side in series, then parallel the sides together? I have the ability to do any configuration with my equipment.
2: What should I do with the stock 50W panel and controller? I was planning to just leave as is, but I also upgraded to Lithium. Since the controller is not able to change selections wont the old controller just be worthlessly charging to only 13.6 volts? Can I wire that panel into my new controller? Should I upgrade that controller?
Thanks for all the help!
You should wire each side in series, then parallel the two sides. Then get a Victron BMV-712 & Victron MPPT charge controller. Put your old panel & controller on Craigslist.

You did not say what size the new panels are. If the are 100w, you can use a 30a MPPT. (400w / 14v = 28.6a)
If they are 170w panels, You should get a 50a MPPT. (680w (170w x 4) / 14v = 48.6a)
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Old 12-04-2021, 09:49 PM   #4
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If 100watt panels I'd wire 2s2p and install a 100/30 MPPT controller and 200ah lithium battery bank. Under good conditions, let's say in Arizona, you would be able to recharge about 125ah per day on average. Of course more in summer than winter and if you can tilt the panels it would help. For solar calculator go to https://pvwatts.nrel.gov/pvwatts.php
I'd also recommend picking up a portable system for parking in the shade.
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Old 12-04-2021, 10:13 PM   #5
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Thanks!
That is a ton of help,
Ill do the two sets of 200w sections
They are 100W panels.

Sounds like that stock solar system is destined for another life.
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Old 12-05-2021, 12:21 PM   #6
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Quote:
Originally Posted by rk06382 View Post
You should wire each side in series, then parallel the two sides. Then get a Victron BMV-712 & Victron MPPT charge controller. Put your old panel & controller on Craigslist.

You did not say what size the new panels are. If the are 100w, you can use a 30a MPPT. (400w / 14v = 28.6a)
If they are 170w panels, You should get a 50a MPPT. (680w (170w x 4) / 14v = 48.6a)
If possible I'd recommend going with a larger MPPT controller than one that closely matches whatever solar array you install.

Reason?

Eventual upgrades. Sooner or later most will want to add more panels so unless your "roof real estate" is totally covered it's highly possible that adding a couple panels will be very tempting in the future.

The added expense of a larger controller now is in the end a lot less expensive than having to replace it later.

Just a suggestion.
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Old 12-06-2021, 12:49 PM   #7
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Your instincts are correct about shading issues and series wiring.

What matters most is the output of the panels (combined) and the gauge of the wire connecting the roof gland to the charge controller and the charge controller to the battery bank.

I have 4 x 100 watt panels, and the rig was pre-wired with #10 AWG wire good for 30 Amps DC...as in the wire comfortably handles 30 Amps with very limited loss. I wired all panels in parallel to allow for shading, because there is no pressing need to wire any in series.

As for the 50 watt panel, you could use it with a charge controller suited to LiFePo4 batteries to connect through your "solar on the side" connection, but it hardly seems worth it. I agree that selling it makes the most sense.
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