Series or Parallel

[mran]

Hi,

I just purchased a Grid Boss, Flex Boss21, 36 x 410W Bifacial panels, and 12 EG4 LifePower4 V2 Lithium Battery – 48V 100AH batteries. I've purchased them from different companies to get the best price.

If anyone can please help, these are my questions:

- Should the panels be wired in Series or Parallel?
- I am ground mounting, wiring wise, does it matter how many panels are in each bank? e.g.: 6 rows of 6 vs 3 rows or 12.
- I had to save for 2 years to purchase this system, I cannot believe the ground mounts are almost as expensive as the panels. I was thinking of using these ground mounts. They would be much easier to mow/weed eat around, and I can adjust the angle of 6 at once. Does anyone have any experience with them and advice?

Tamarack Solar UNI-PGRM/6P2 Economy Horizontal 6 Modules Top of Pole Mount

Tamarack Solar UNI-PGRM/6P2 Economy Horizontal Top of Pole Six 60 or 72 Cell Modules Mount Designed and Engineered to Mount One Solar Module Horizontal

www.solar-electric.com

I have an electrician coming to install the Gridboss next week so I am trying to get everything ready to install and setup the rest.

Thank you for any help you can give.

Mark

 

[hybe022]

you have datasheet of the 410W bifacials?
I am thinking 36 panels = 12S x 3 each MPPT, but i might be wrong.

i use a aluminum roof mounts for my installs in my country.
mounting is about 35% of the panel price.

 

[ricardocello]

I cannot believe the ground mounts are almost as expensive as the panels.

Actually, I find that ground mounts cost more than the panels these days.

I did my own DIY ground mounts with unistrut and aluminum penetrators, and even so, that was a lot more money than I was expecting.

 

[mran]

you have datasheet of the 410W bifacials?
I am thinking 36 panels = 12S x 3 each MPPT, but i might be wrong.

i use a aluminum roof mounts for my installs in my country.
mounting is about 35% of the panel price.

Hi,

Does 12S mean 12 in series?

I've attached the datasheet.

 

[hybe022]

i'm 99.9% certain he's gonna wire it 12S to each mppt.

12s = 12 series

 

[mran]

i'm 99.9% certain he's gonna wire it 12S to each mppt.

The electrician is only installing the Gridboss. I was hoping I would be able to take care of the rest. I've watched every installation video I can find for this, and written down the step by step instruction I could find. I am starting with the manuals today however I don't have any information on how to best wire the panels.

 

[hybe022]

wiring it 12series to each mppt is safe.
in the future, if you happen to want to add more panels, you can parallel 2 strings to MPPT1 & 2 as it can accept more current input.

 

[ricardocello]

Does 12S mean 12 in series?

Yes, when you see things like 12s3p here, that means you put 12 panels in series, and call it a string.
Then you put those three strings in parallel. Series: Add Voltage. Parallel: Add Current.

The FlexBoss21 has 3 independent MPPT trackers, so you have to determine how to divide the panels between them.
The ideal maximum voltage going in is 440 VDC according to the specification sheet.
The nominal voltage should be about 360 VDC. Never exceed or even get close to 600V or they will fail.

The Voc of your panels at 25 C is 37.67V.
If you put 12 in series, that would be 452V, which seems right to me (thanks @hybe022).
This leaves plenty of voltage headroom for extreme cold temperature.

The max short circuit current is 31A, 31A, 19A for each of the three MPPT trackers.
The Isc of your panels at 25 C is 13.11A.
Putting two of the 12-panel strings in parallel is safe. Maybe put the third string of 12 on the next MPPT tracker.
Or put each string on its own MPPT tracker.

So you can do {12s + 12s + 12s}, or {12s2p + 12s}, depending how you want to split up the 36 panels.
You cannot do 12s3p because it would exceed the allowable short circuit current.

 

[yabert]

I cannot believe the ground mounts are almost as expensive as the panels

Yeah! it's the sad reality as now the panel are so affordable.
Don't hesitate to share pictures of your set-up.

 

[mran]

Yes, when you see things like 12s3p here, that means you put 12 panels in series, and call it a string.
Then you put those three strings in parallel. Series: Add Voltage. Parallel: Add Current.

The FlexBoss21 has 3 independent MPPT trackers, so you have to determine how to divide the panels between them.
The ideal maximum voltage going in is 440 VDC according to the specification sheet.
The nominal voltage should be about 360 VDC. Never exceed or even get close to 600V or they will fail.

The Voc of your panels at 25 C is 37.67V.
If you put 12 in series, that would be 452V, which seems right to me (thanks @hybe022).
This leaves plenty of voltage headroom for extreme cold temperature.

The max short circuit current is 31A, 31A, 19A for each of the three MPPT trackers.
Putting two of the 12-panel strings in parallel is safe. Maybe put the third string of 12 on the next MPPT tracker.
Or put each string on its own MPPT tracker.

So you can do 12s + 12s + 12s, or 12s2p + 12s, depending how you want to split up the 36 panels.
You cannot do 12s3p because it would exceed the allowable short circuit current.

That is extremely helpful, thank you!

 

[MikeInKingman]

They also have a String Calculator available:

SolarPanelApp

eg4electronics.com