diy solar

diy solar

Series or Parallel? -- that is the question.

dpdoug

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Oct 3, 2019
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I guess everyone has seen this question: Should I wire my panels in series or parallel? I have 2 12V 100W panels and a 12V 200Ah LiFePo4 battery. The Solar charge controller is a 40 amp MPPT. What is the best way to hook them up?
 
That combination of hardware can have only one answer, series. MPPT controllers need a bit of space to work in so you need the higher voltage. I'll assume you have a controller that can handle the panel's VoC in series. It'd be hard to find one that won't handle 2 x 12v in series, but I'm sure they are out there.
 
Those panels are technically 80 watt panels. In my tests.

And yes, they have bypass diodes, and considering only 2x, gnubie is right, series is the way to go.
 
Hello very new to this but am liking it, Would the same suggestion above apply for 4 x 100 watt panels going to 50a charge controller with a max of 80v?
 
It all depends on the panel specs. Can you post a link to your panel's specs, or a picture of the label on the back where some of the specs are listed?
 
Started to gather these last couple of years before i knew i wanted to get into this :)

2 x 100 Watt Rich Solar
Specifications
  • Maximum Power(Pmax): 100W
  • Maximum Power Voltage(Vmp): 18.2V
  • Maximum Power Current(Imp): 5.49A
  • Open Circuit Voltage(Voc): 22.1V
  • Short Circuit Current(Isc): 5.86A
  • Maximum System Voltage(Vmax): 600V DC
1 x 100 Watt Windy Nation:
https://www.amazon.com/WindyNation-...126&sprefix=windy+nation+solar,aps,314&sr=8-3

1 x 100 Watt Renogy:
 
If you have those 4 panels and have to work with no more than 80v, connect two panels in series and then parallel those sets. That'll give you approx 44Voc and a peak of approx 22 amps.

If you want to, post a link to the charge controller and I'll check the voltage ratings of it.
 
OK, 80v so I'm guessing you have a 12v battery so that 2 x 2 panel configuration will work for you.

If you have shading issues you could put the panels in parallel but the MakeSkyBlue may never go into MPPT mode because of the PV and battery voltage being fairly close.
 
While I have you here im looking to switch to a 24v system I was either going to change my inverter to the Giandel 2000/24 or going for an all in one like the MPP solar one. would you mind sharing your thoughts?
Thanks
 
The MSB will handle stepping up to 24v and then your maximum PV Voc will go up to 105 so you can reconfigure the array for series if you wanted to. That would make wiring more convenient but the maximum current from your array will fall to 5.29 amps as the current rating of the lowest panel sets the pace in series operation.

I have a V117 MSB charger and the firmware has problems such as getting stuck in mode 7 at sun up. The MSB also has no external current sense so if the load is on the battery it (v117 at least) never exits absorption charging since it doesn't see current fall of to what ever it's internal check value is and that's not good for battery life.

I don't have a MPP but they seem reasonably well regarded here but buy from a local distributor rather than price hunting on ebay. Buying direct from overseas usually means you have to live with no warranty. The PV MPPT input rating of the smaller MPP units is 105 I think so you are OK there with what ever you decide to do with the panels, all series or 2 x 2.

I have a Giandel 2000/24 and it hasn't blown up yet and will run my 2kW kettle to boil a mug of water. They have changed their lineup lately I think so not sure about the quality now.
 
Awesome Gnubie you have put me back on a straight path i was lost for a moment there, now i see why ive been stuck in mode 7 as well and i went to check my MSB only to find that im running (v113) :( now that makes it a must for upgrading so the question is new charger + inverter or MPP 2400 grrrrr i hate being on the spot like this, I wast ready LOL but than i dont want my batteries damaged. MSB has the new (v119 wifi) not sure if they fixed the quirks on that or just switch to the EPEVER MPPT.
 
Those v119 units are way over priced IMO considering the performance of the previous versions, and it still can't make use of an external current shunt to monitor charge current.
 
So how do you deal with the stuck in mode 7 issue as to not cause damages to your batteries?
 
I have an arduino board monitoring it. If it sees it stuck it pulls the reset line down momentarily. It doesn't fix absorption charging never ending though. This is a spare controller, I use Victron for the stuff that matters.
 
I’m upgrading my small system and based on the comparison test that Will did on the 4 most popular solar panels on Amazon I purchased an 100w HQST panel to connect with my existing Renogy 100w panel (Less than 2 years old). Is it ok to connect these in series.
 
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