Multiple solar panel types: how to isolate them?

[stevemaller]

On my Sprinter right now I have one fixed 400W solar panel which is confirmed to output 400+ watts under ideal conditions. This panel is wired into a Victron MPPT 100/50 and feeding a bank of 3x100A 12V LiFePo4 batteries. I'd like to add solar capability because I've installed a Velit 12V air conditioner, and given the limited roof space, I'm considering going with a folding panel, specifically a big one like the 600W AllPowers one (https://a.co/d/au6kCUZ) that I could drape over the windshield and hood withe the van pointing towards the sun.

I know the panels are going to have very different outputs because of their characteristics and orientation. Does it make sense to simply wire the additional panel into an additional MPPT Solar Controller so I don't have to worry about the string voltage issues and one of the panels crippling the other? It seems like that's the simplest way of isolating the panels from each other.

Or am I missing something? Here's a photo of my rooftop right now...thank you!

 

[Hedges]

You can use multiple MPPT, of course.

If you have multiple panels (or strings of panels) of similar Vmp, it is OK to connect them in parallel even if their orientation is different. The ones without direct sun won't pull the ones in direct sun down. Voc of a shaded panel is similar to Vmp of a panel in direct sun. (if in a pitch black room, they would somewhat)

(in series, all should be same orientation.)

If more than 2 panels (or strings of panels) in parallel, they should each have a fuse.

 

[stevemaller]

You can use multiple MPPT, of course.

If you have multiple panels (or strings of panels) of similar Vmp, it is OK to connect them in parallel even if their orientation is different. The ones without direct sun won't pull the ones in direct sun down. Voc of a shaded panel is similar to Vmp of a panel in direct sun. (if in a pitch black room, they would somewhat)

(in series, all should be same orientation.)

If more than 2 panels (or strings of panels) in parallel, they should each have a fuse.

Thank you. If I parallel them and both panels are producing near optimally, I think I may be over the current of the MPPT 100/50, right? 1000W at 12V is 83 amps, right? Series would be a better fit for that box, but it sounds like that's not a good idea with different panel types and orientations.

Sounds like I should go with another MPPT for the foldable panel.

 

[Hedges]

Series or parallel into an MPPT is the same watts, and the limit on output current would be the same.
If series, watch Voc, with adjustment for cold weather. Make sure you never exceed the 100V absolute max.

How about parallel, but quite different orientation?
Then they won't both be peak current at the same time, could fit better within MPPT limits.
And how often do you get full direct sun? Flat on roof of an RV is off-angle most seasons.


Portable is good so you can park in the shade and put panels in the sun.
An extra MPPT is good to have, but if same voltage as existing system, might get away with sharing same one.

 

[stevemaller]

Series or parallel into an MPPT is the same watts, and the limit on output current would be the same.
If series, watch Voc, with adjustment for cold weather. Make sure you never exceed the 100V absolute max.

How about parallel, but quite different orientation?
Then they won't both be peak current at the same time, could fit better within MPPT limits.
And how often do you get full direct sun? Flat on roof of an RV is off-angle most seasons.


Portable is good so you can park in the shade and put panels in the sun.
An extra MPPT is good to have, but if same voltage as existing system, might get away with sharing same one.

Such excellent information. Sounds like I should play with some different scenarios. My goal is to be able to go net positive solar while running the A/C in the heat of the day so I have enough battery to get through the night running lower A/C. The numbers look good if I can keep batteries topped off during the day.

You sound like a true professional. I appreciate your expertise.

 

[Hedges]

Thank you,

A number of people on the forum with experience using PV, a variety of brands, and some for your RV application.
Including pure DIY, engineers, contractors, etc.

 

[pollenface]

I isolate my different panel groups by having them on their own SCC with their own breakers, etc.

1.52kw/93v on Victron 100/20
1.43kw/93v on Victron 100/20
1.56kw/124v on Victron 150/35