9 replies to this topic

[Oakleyrossi]

Looking for some feedback on the best way to utilize a Renogy fixed 100w panel on the roof and have the ability to add a Renogy 100w portable panel as needed off the rear. Charge controller is a Victron MMPT 100/30. What is the best way to set up the connection at the charge controller? Series or parallel?
Thanks. I have gotten so much amazing info here and it’s all appreciated.

[billharr]

Parallel is plug and play if hooked to the Victron controller. Be sure you do not have a controller on the portable panel, remove if you do. Series will take some switching to use. 

 

Edit, if you want to use the portable panel's controller wire it to the battery. 

Edited by billharr, 04 April 2019 - 04:46 AM.

[Oakleyrossi]

Thank you. That’s kind of what I thought but wanted to double check first. No controller is n the portable so all good.

Appreciated.

[smlobx]

Parallel is plug and play if hooked to the Victron controller. Be sure you do not have a controller on the portable panel, remove if you do. Series will take some switching to use. 
 
Edit, if you want to use the portable panel's controller wire it to the battery.

Pardon my stupidity in all things electric but I’m trying to do the same thing.

My portable panel does not have a controller
https://overlandsola...g-solar-charger
So does that mean + to + and - to - into the back of the of the existing controller?

[donks2]

Question on this, too! If both panels are 12v, but different watts, can they still be wired in parallel tot he controller? We'll be using 175w Newpowa on the roof, and not sure on size of portable. TIA!

[Vic Harder]

It depends... it always depends!  

 

This article is pretty good - and has nice visuals.

https://solarpanelsv...g-solar-panels/

 

It isn't the watts that are critical, but the current/voltage output of the differing panels.

 

The wiring is easiest if you want to hook two different panels/arrays  up in parallel.  Let's say a single roof mounted panel is one array, and wired in parallel.  Simple, as the negative from the solar panel goes to the negative on the controller, same with other terminals, positive to positive.  

 

The portable would then plug into the exterior plug on the camper, and those wires would also be going neg to neg, pos to pos.  Thus, both panels would be in parallel.  As the above linked article says, do this if the voltage outputs of the panels are close ... or at least more similar than the current outputs, since the current outputs of each panel don't matter if they are in parallel.  If the current outputs are vastly different, then serial is likely the better option.

 

To do a serial hookup, the initial wiring is more complicated, as the wires from the rooftop panel need to go "through" the external port on their way to the controller.  And you will either need a switch somewhere close to the external port that connects the two sides together when the external is not plugged in... and needs to be flipped before plugging in the external panel or sparks may fly.

 

I'd use a small dongle to plug into the external when the portable isn't plugged in to be the "switch".  That way, when you want/need the extra oomph from the portable, you would remove the dongle and plug in the external.  Voila, serial connection made.

 

Make sense?  Pictures/diagrams would be helpful...  I think. I might whip something up shortly, but no longer have any nice software on my PC to do that with.... 

[Oakleyrossi]

Thanks Vic.....makes sense and super helpful.

[billharr]

It depends... it always depends!  

 

 

 

I'd use a small dongle to plug into the external when the portable isn't plugged in to be the "switch".  That way, when you want/need the extra oomph from the portable, you would remove the dongle and plug in the external.  Voila, serial connection made.

 

 

I like "It depends... it always depends."   I think as long as your panels were sold as the same voltage (say 12v) you are ok to use together. If you have a 12v and a 24v then "it depends."

 

The dongle is so simple I may have to do some rewiring. I have 100w and 150w 12v panels on the roof wired in series. Have not used my 120w solar in a bag because I did not want to mess with wiring in switches. Going to try the dongle way. 

Edited by billharr, 05 April 2019 - 03:26 PM.

[donks2]

Thanks for this link, very helpful. Slowly these concepts are coming together! I did the math on series vs parallel with the 175w fixed and 100w panel portable and the loss much less in parallel (260w total in parallel vs 205w in series) plus easier wiring.

 

Boy, does it 'always depend'!

 

 

It depends... it always depends!  

 

This article is pretty good - and has nice visuals.

https://solarpanelsv...g-solar-panels/

 

It isn't the watts that are critical, but the current/voltage output of the differing panels.

 

 

[buckland]

Thanks Vic... If I don't read a thread like this every few months I forget! That means my foundation knowledge in electric is on shaky ground. Probably always will be at my age. But this is real clear and will save it to reread to reassure when I add that second panel!