Are these panels compatible in parallel?

[Millerbread]

I've got a Renogy 100W 12v monocrystalline solar panel and a flexible 50W panel. Should I even bother putting these two things together for a roof mount on an overlander? I guess my specific question is how much of a delta between voltages is too much?

 

[Fred S]

In series you'll get a MAX of 18+18=36v and 2.8a => 100 watts (operating watts).
In parallel you'll get a MAX of 18v and 2.8+5.7=8.5a => 153 watts.
Parallel is also preferred when the panels happen to have the same operating voltage, like these do. So it looks like in this case, two is better than one.

 

[Millerbread]

In series you'll get a MAX of 18+18=36v and 2.8a => 100 watts (operating watts).
In parallel you'll get a MAX of 18v and 2.8+5.7=8.5a => 153 watts.
Parallel is also preferred when the panels happen to have the same operating voltage, like these do. So it looks like in this case, two is better than one.

So what you're alluding at is, despite the delta or differences here in operating voltage it's still OK to run these together? I'm not taking a significant loss or anything by it?

 

[grizzzman]

In parallel around 1 volt, simply put your fine.

 

[Hedges]

One says Vmp = 17.6, the other Vmp = 17.9; very close.

If you can locate data sheets with curve of current vs. voltage or power vs. voltage you'll probably find that even operating a couple volts off MPP results in little loss.
To the extent the cells are of different technology, and the panels have different lamination materials, their curves may respond differently to varying temperature and angle at which sunlight hits them.

Cool is better, so allowing airflow underneath could help.
Flat on the roof doesn't present as much area to the sun, so if your mount allows you to tilt them toward the sun while parked you'll get more power. Much bigger difference than having different panels of the same voltage paralleled, especially in winter when the sun is low.

Oh, and what kind of charge controller? If PWM I think the differences between panels is moot because both are clamped to the battery voltage. Only MPPT makes a difference because then the panels will be at 17.6V not 12 ~ 14V. That would increase power output as much as 10% based on the curves for a 12V panel I have.