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Author Topic: Series or parallel?  (Read 753 times)


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Series or parallel?
« on: October 30, 2017, 05:48:50 PM »

I pretty much have my solar set up ironed out.

Iím using the following components:

4 GC2 batteries for 440 ah capacity
4 100 watt flexible solar panels
Victron Energy 150volt 35 amp MPPT charge controller

My dilemma is to how to wire the panels, all 4 in series for a voltage of around 72, or do two pairs in series then wired in parallel for a 36 volt output?  He controller can obviously easily handle either.

Iím thinking the higher voltage would be desired as 10 gauge wire would be plenty, most charts Iíve found are 12 gauge would be sufficient for 10 meters.

Any experience or opinions?

2006 GMC 1500 4x4 Crew Cab 5.3L
2018 Rockwood 2509S


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  • Posts: 3663
Re: Series or parallel?
« Reply #1 on: October 30, 2017, 06:17:28 PM »
You have stated the wattage,, but what is the VOLTAGE of each panel??>>>Dan
Vary rare American Tradition 38TT/330 turbo Cummins
Last year Jeep liberty 4 down
72 VW Baja 4 down
Cedar City, Utah
USAF vet. 59-63
FMCA F312919
The difference between intelligence & stupidity is: intelligence has it's limits
      Albert Einstein.

PJ Stough

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  • Posts: 1722
Re: Series or parallel?
« Reply #2 on: October 30, 2017, 06:23:19 PM »
The biggest issue with solar panels is shading.  If no shading, then look at the specs of the controller to find the optimum voltage to decide if parallel or series is better.  Also, look at a voltage loss chart to see if 36 volts will be adequate for the wire being used.
PJ Stough   Iowa
2005 Winnebago Voyage 38J


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  • Posts: 69
Re: Series or parallel?
« Reply #3 on: October 30, 2017, 08:34:30 PM »
Thanks, I've read through the manual again for the charge controller and it doesn't list an optimum voltage.  I think I'm going to wire each pair in series, then parellel the pairs to hopefully reduce the effects of shading.  The only spec that the manual gives for voltage is the PV voltage must be at least 5 volts higher than battery volts to start the charging sequence, and that 150 short circuit volts is the max the controller can handle.  I think we'll run with the 36ish volt set up.  Shading isn't too much of an issue with my roof set up, but there are usually trees around when I'm camping that depending on the time of the day could shade a poriton of the roof.

Dan, the panels are 20 volts short circuit and 17.8 volts max power volts.  Sorry I wasn't clear on that, I figured listing the volt specs at roughly 72 in series or 36 in series-parellel would have given away the panel voltage.

2006 GMC 1500 4x4 Crew Cab 5.3L
2018 Rockwood 2509S


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  • Posts: 1665
Re: Series or parallel?
« Reply #4 on: October 30, 2017, 09:23:48 PM »
I think that using the series/parallel combination is a good way to do it.  If they were all in series than a shadow could seriously reduce the output of the panels.

I have about 1500 watts in 10 panels distributed between two roofs, (the DP and the Stacker.

They charge three separate battery banks thru four charge controllers.

One system has 750 watts of panels, (the DP). It is effectively a series /parallel system by having three panels, (450 watts), in series into one Charge controller and the other two panels, (300 watts). in series again with a separate charge controller feeding the common battery bank.  If one set is effected by shade it does not reduce the other charging system.  It is kind of like pouring water into a barrel from two hoses.  This system uses Blue Sky controllers in a networked system with one as the Master and the other controller as a slave remote.  It also has the Blue Sky version of the Trimetric Monitor.

The Stacker has a similar system except that it feeds into two separate battery banks again three panels on one and two panels on the other with separate charge controllers and two monitors.

One of the battery banks handles the normal lights, a electric pump for the hydraulic car lift, and a small chest freezer.
The other bank provides power for any tools in my workshop and it also keeps my electric golf cart always topped off. Both of these systems in the Stacker have 1,000 watt invertors.

The total number of batteries is 14 T105s and 2 Optima Blue Tops.  Six of the T105s are in the golf cart all the time.
« Last Edit: October 30, 2017, 10:15:04 PM by HueyPilotVN »
Bill Waugh
40' Country Coach DP
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