Adding to my Solar Array - Keep 1 controller or go to 2?

Jun 5, 2012
144
Catalina 30 mkI Victoria, British Columbia
Hi all,
I have been given a couple of extra panels that I'd like to add to my existing setup. They weren't what I would have chosen if I was buying... but free is free! My question is how best to set up the new additions. Here's the details:
Current Setup
  • 2 - 60W panels, wired in Parallel to provide (a theoretical) 18.0Vmp, 3.43Imp
  • Connected to Genasun GV-10
  • Monitoring of my 210Ah Golf Cart battery (12V) system is done with a Victron BMV. I also have an 'emergency only' starter battery that is kept topped up with an SI-ACR.
New gear
  • 2 - 50W panels, with the following specs 15.9Vmp, 3.15Imp
I know that if I add these to my current parallel setup I now limit the system voltage to 15.9V. The GV-10 should still be OK with the total Imp, (the 'volume' of available energy from the panels), but I've lost some significant 'pressure' pushing it in from the Voltage drop.
So... Should I accept this loss in voltage for the gain in amps, or will the fact that I have lost it make the final charging stages of my batteries more difficult because they will resist 15.9 much more easily than 18.0
I also have an older Sunsaver 6 PWM that I could throw into the mix if it would help.....
Thanks for your thoughts

Mike
 
Nov 14, 2013
200
Catalina 50 Seattle
Assuming you don't have big shading issues, I'd put one new panel in series with one old panel and get a second GV10 so you'll have one controller for each pair. Unfortunately, your GV10 maxes out at 140W so you can't parallel the two series pairs into the existing GV10.
 
Last edited:
Jun 5, 2012
144
Catalina 30 mkI Victoria, British Columbia
your GV10 maxes out at 140W so you can't parallel the two series pairs into the existing GV10.
Ah ha! Good point, I had been doing my math based on rated current, and didn't check on the maximum allowable panel wattage...
Thx for that.
 
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Feb 6, 1998
11,667
Canadian Sailcraft 36T Casco Bay, ME
I would suggest keeping the two pairs separate and invest in a new controller for the free panels...
 
Nov 14, 2013
200
Catalina 50 Seattle
I would suggest keeping the two pairs separate and invest in a new controller for the free panels...
Just curious what you see as the advantage of this configuration over two pairs of one old and one new.
 
Feb 6, 1998
11,667
Canadian Sailcraft 36T Casco Bay, ME
Just curious what you see as the advantage of this configuration over two pairs of one old and one new.
#1 His GV-10 can only handle a maximum of 140W
#2 The GV-10 can only handle 34V so series is out on the 18V panels.
#3 His panels are differing voltages which is less than optimal for MPPT performance when paired in parallel.
#4 The Genasun GV-10 controller was specifically designed to maximize a one controller per panel install or matched pairs below 140W / 34V..

My recommendation would be adding a second GV series for the lower voltage panels. MPPT performance won't be great with a 15.9V panel but better than PWM. A cheap PWM will work, just not as well as a GV series.
 
Nov 14, 2013
200
Catalina 50 Seattle
Agreed on all counts but what I was suggesting was series pairing one 18V/60W panel with one 15.9V/50W panel, thereby staying below the 140W/34V limit of the GV-10 while maximizing the available MPPT charging voltage. With a second GV-10, he'd have two well-matched parallel solar charging sources.
 
Feb 6, 1998
11,667
Canadian Sailcraft 36T Casco Bay, ME
Agreed on all counts but what I was suggesting was series pairing one 18V/60W panel with one 15.9V/50W panel, thereby staying below the 140W/34V limit of the GV-10 while maximizing the available MPPT charging voltage. With a second GV-10, he'd have two well-matched parallel solar charging sources.
You don't want to series pair two mismatched panels. Heck you don't really want to parallel two mismatched panels either.
 
Nov 14, 2013
200
Catalina 50 Seattle
Okay, thanks for the response. I can understand not paralleling a higher voltage panel with a lower voltage one but I've never seen an issue putting them in series.