Wiring different solar panels in series?

Photomom

I have a 100 watt Goal Zero solar suitcase that I’ve adapted to plug into the Zamp port, and I just installed a Renogy 100 watt flexible panel on my roof. I have a Victron SmartSolar 75/15 controller, and I’ve wired everything with quick disconnects so I can plug EITHER of the solar panels into the controller.

I’m thinking that it might be possible to wire the panels in series by creating a wiring harness using additional quick disconnects.  See attached image. The pink part of the circuit shows the wiring harness that I’d make.

This would let me add the portable panel to the rooftop panel when we are set up at camp. 

Why wouldn’t this work?

GatorEgg

Obviously wiring in series will double your voltage.  Is your system setup for 24volts? 

Photomom

GatorEgg said:

Obviously wiring in series will double your voltage.  Is your system setup for 24volts? 

This solar controller will handle 75 volt input. It’s an MPPT controller and knows that I have a 12 volt battery. 

Photomom

Electrically it “should work”. But would it be a problem that the panels are two different brands?

SteveK

The problem is that you will be limited by the lowest current solar panel.  This means that if one panel is in shade, the maximum current you will get will be current produce by the shady panel.  When in series, the current in the two panels is identical, by definition.  You would be better off to wire the panels in parallel and get the sum of the current rather the the higher voltage.

Photomom

SteveK said:

The problem is that you will be limited by the lowest current solar panel.  This means that if one panel is in shade, the maximum current you will get will be current produce by the shady panel.  When in series, the current in the two panels is identical, by definition.  You would be better off to wire the panels in parallel and get the sum of the current rather the the higher voltage.

Thanks, the idea would be to use both if the trailer was in the shade and I could put the portable panel out in the sun. It may just be better to hook up the portable panel using the quick disconnect instead of the roof panel. 

I haven't found any explanation as to why using two different brand panels would work, or not work. Do you have any knowledge about that?

rfuss928

The system you describe will have the same wiring lengths and currents which ever option you choose so there will be no advantage to the series connection. 

IMO - Because the panels by design will generally be exposed to significantly different conditions, parallel connection would probably be prudent.

Either way will work so try both.  I expect there will be very little difference, if any.

Have fun....

Bob

Cbusguy

Probably a bad idea to wire panels from two different manufacturer in series.....   Different resistances and voltages.

Keep in mind you are limited by your weakest panel when wiring in series.

Wiring in parallel removes all of that and they can work sort of independant