simplysolar avatar image
simplysolar asked

New RV Roof New CIGS panels New Smart Solar 250/85 MC4 ?'s

Hey folks,

I have a 2018 Keystone Raptor with 17 total Renogy flexible panels.

With an additional 6 panel array mounted cantilever on frame off of the rear toyhauler ramp frame.

I have 3 smart solar charge controllers 150/60, 150/85 & 150/60.

now the roof needs a tear off and new decking and a new skin.

So obviously now's the time to make changes if any time there ever was.

The renogy panels did not last. Down below warranty specs drastically.

So I've been researching the NEW CIGS panels from miasole. They have excellent performance, weight, flexibility, shade tolerance (24 bypassing diodes), excellent output, damage resistance (can actually walk on them really) and ABILITY TO SUSTAIN DAMAGE (I'VE SEEN THEM HIT FULL FORCE WITH A BASEBALL BAT AND SHOT WITH A PISTOL AND STILL OUTPUT GREAT POWER). They been installed commercially on TPO and metal roofing and automotive / trucking fleets. Utilizing the Heliobond adhesive they stay where you put them and no through the roof mounting is necessary.

So I'm sold on these panels

Now the problem.

They have much MUCH HIGHER Vmp 67.2 and Voc 85.6. ALL at 265w & tolerance +10/-0w

6 total panels of 19.5 feet by 1.2 feet on the roof.

So the only way I can series connect any of them is with a NEW 250/85 smart solar mppt. Only two can be series and only 2 arrays of 2 panels to this mppt total possible pwr 1060-1100w (I'm on 12v batt and staying there, no changes there, I have my reasons..) else overpower limiting by the 250/85 if I connected another string I'd be severely wasting power and creating heat dissipation from too much applied power.

(in series 2, two series arrays in parallel at the MC4's)

I can use my 150/60 for the remaining two panels on the roof. (parallel to MC4)

I also have two additional 500w CIGS panels coming, Vmp 62.4 Voc 77.2

and they total up to 8.5x8.5 feet and I'll mount on my portable cantilever array system when we are fixed and not mobile like currently/now. I'll use the 150/100 and they'll have to be paralleled but out close to the panels.

Now the question...

I've always series connected my arrays and carefully adhered to total Voc being below 150.

NOW I'm going to have to be paralleled a lot....

most of these connections due to higher Voc's of these panels.

All installed panels will be matched in specs in the series/parrallel connected controllers.

All panels connected to individual controllers will be located close to each other on the RV roof. 4 on Left top side to the 250/85 and two on other side of roof to the 150/60 or 150/85.

Am I going to see a lot of losses due to parallel connections on the MPPT's?


WE3RV amatuer radio will be my new callsign late Feb 2024.

currently I'm W0TKO


installationsmart solar charging behaviour
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3 Answers
JohnC avatar image
JohnC answered ·

Hi @simplysolar

Parallel them all. Each panel is only ~4A at Vmp and should show no losses. MC4 connectors are rated to 30A (Not suggesting you go that high though).

Just because you always seriesed them before doesn't mean you have to keep doing it. The replaced panels were likely only low Vmp panels and were easier to wire that way. The new ones are already internally series cells.

The existing mppts will be fine.

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Paul B avatar image
Paul B answered ·

you should not see any losses caused by the mppt units by using parallel and in fact due shading from time to time it maybe better . the only reason to go series is it reduces the amps down the PV cable. thus less losses in the cable or you can run smaller cables

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simplysolar avatar image
simplysolar answered ·


thanks for the quick answer, seems like a waste to ADD a 250/85.

I'll parallel y branch them on the roof and even save on wire.

I'll be in specs using the 150/60 and 150/85 for the roof mounted panels 3ea 265w to each controller.

I'll use the 150/100 for the 2ea 500w portable array.

thanks again.

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