Mixed Solar Panels

[Lagotto]

I would like to fit a fixed Solar Panel to my motorhome roof but have limited space, hence a max of 200w with a MTTP controller charging twin leisure batteries only (have battery master fitted). I also have a portable folding 100w panel fitted with a PWM controller (Photonic Universe) which I can quick connect direct to batteries. If I have the fixed panel connected and running, would I have a problem if I then connected the portable to the batteries at the same time?

 

[tonyidle]

No. Although you will gain more by connecting your portable panel to the input of your MPPT regulator in parallel with the existing panel. (miss out the portable regulator altogether)

 

[Lagotto]

No. Although you will gain more by connecting your portable panel to the input of your MPPT regulator in parallel with the existing panel. (miss out the portable regulator altogether)

Ok, so disconnect the portable panel output wires from the solar controller input, then remove the output wires from the solar controller, join each of the two pairs together so I now have a long cable coupled direct. Then where this cable connects to the mating cable in the motorhome, I disconnect this from the two batteries (+ on battery 1 and - on battery 2) and instead connect to the same input as the roof panel. Thus the MTTP controller will be seeing combined voltage from both?

 

[tonyidle]

Ok, so disconnect the portable panel output wires from the solar controller input, then remove the output wires from the solar controller, join each of the two pairs together so I now have a long cable coupled direct. Then where this cable connects to the mating cable in the motorhome, I disconnect this from the two batteries (+ on battery 1 and - on battery 2) and instead connect to the same input as the roof panel. Thus the MTTP controller will be seeing combined voltage from both?

Correct. Its the same as combining different size panels on the roof and retains the advantages of the MPPT controller.

 

[Hoovie]

1. You have not told us what the rating of the MPPT Controller is. You may be exceeding the rating if you add another 100W on top of the 200W on the roof.

2. You cannot automatically assume you can mix solar panels and get the full rating of all the panels together.

To give a considered answer, need to know the following...

What is the rating of the MPPT controller? Max Current, Max Voltage, Max Power​

What are the specs of the Solar Panels on the Roof - Max Voltage, Max Current (note - not the Voc or Isc, but the MAX numbers)​

What are the specs of the Solar Panels in the Photonic Kit - same info. These are probably a pair of 50W panels connected in parallel. Info will be on the back of the panels.​

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[Lagotto]

1. You have not told us what the rating of the MPPT Controller is. You may be exceeding the rating if you add another 100W on top of the 200W on the roof.

2. You cannot automatically assume you can mix solar panels and get the full rating of all the panels together.

To give a considered answer, need to know the following...

What is the rating of the MPPT controller? Max Current, Max Voltage, Max Power​

What are the specs of the Solar Panels on the Roof - Max Voltage, Max Current (note - not the Voc or Isc, but the MAX numbers)​

What are the specs of the Solar Panels in the Photonic Kit - same info. These are probably a pair of 50W panels connected in parallel. Info will be on the back of the panels.​

Thanks for the replies guys, good info. I have not purchased the roof panel yet, or the controller, as I first wanted to get a good idea on the feasibility. Now I know the method and wiring I can spec the roof panel (size to fit my space available) and the controller (spec to meet the combined panels). I have the necessary info on my current Photonic panel, quite right, a pair of 50w so can spec everything else to suit. Initially I would have liked to have more solar on the roof, but as that is not possible, the next best alternative is to use what I already have combined with a new panel. I understand that it wont be the the ultimate solution, but will give me a pretty decent set-up, albeit not the max as rated.