On a MH roof you have some large spaces and some smaller spaces or spaces with possible shading issues that you would want to avoid. Can you mix panels of different physical sizes / wattages, but of the same Mfg, voltages, etc?Bill

Yes you can parallel eg, a "12v" 160w panel with a 12v 100w panel for an array of 260w. BUT you cannot mix voltages such as add a 12v 100w panel to a "24v" 255w panel.Better not to mix mono and poly either--they act a little differently in low light. Can be done though.You can have a 24v set of panels with its own MPPT controller and another set of 12v panels with its own PWM controller, set both controllers to the same high set point voltage 14.8v eg, put both controllers on the same battery bank, and they will add their amps.

What controller do you plan to use?Generally in parallel you need to match Vmp as best you can while in series you want to match Imp.

Yes try to match Vmp in parallel for mppt, or more generally just match the # of cells (36, 60, 72).

time2roll wrote:What controller do you plan to use?Generally in parallel you need to match Vmp as best you can while in series you want to match Imp.I don't know which controller yet, have just been up on the roof measuring the open spaces a couple of times to see what I might fit in. I would like to be around 1,000W so I don't have to redo anything later. That could be overkill, but I know it will take care of me.Bill

1000W will not be an overkill. Some places are warm but cloudy and/or rainy, and then 1000W works like 200W. With 1000W it is often easier to use MPPT controller and series connections, or series-parallel, for higher voltage and lower amps. Ex, one string 4*120W series, and the second same string in parallel to this.In such a string you can replace 2*12V panels 120W each with one 24V panel @240W-250W, with some loss of efficiency.1000W array is (potentially) 70-75A output post-controller. In this range it will be likely MPPT, not PWM. I recall Midnite Solar have some 90A units. You might also get away with Morningstar TS MPPT 60, from what I hear it's a better value than Midnite. Input voltage of array MUST not exceed the controller limit. In Wa you won't need more than 60A controller.Make cardboard templates the size of 100 or 120W panels, - won't be easy because they are often different shape, some long and some square. In 24V panels there is more order, 240-280W panels are mostly 65" by 40". Go on the roof and play with those pieces.One thing to be careful with, if you like high elevations in winter (I don't). High voltage in series could spike dangerously high when it's cold and sunny.

Mixing solar panel sizes | Good Sam Community

brulaz
Explorer
Mar 14, 2018
BFL13 wrote:

...
BUT you cannot mix voltages such as add a 12v 100w panel to a "24v" 255w panel.
...

But you can put two 12V 36 cell panels in series, and if their combined Vmp is close to that of a 24V 72 cell panel, you can parallel the series pair with the 24V 72 cell panel.

Haven't done it actually, but it makes sense, I think. The two 36 cell panels are just a 72 cell panel split in half.
Almot
Explorer III
Mar 14, 2018
Portables are a lot more trouble. They become inconvenient in sizes bigger than 200W, and storing them in a bus is more inconvenient than in a truck. One benefit I can see is that you can (sometimes) get a portable out of the shaded spot where your rig is parked.
MDKMDK
Explorer
Mar 14, 2018
A portable can more easily wander off, if not properly secured or watched. Another minor drawback.

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