One MPPT 3 strings mixed panels

[Bendesa1962]

Hi all,

My question is as follows.

Inverter 30 kWp

2 x MPPT
6 x DC connections for Strings 3 per MPPT

At the moment the situation is as follows:

MPPT 1 3 strings of 20 pieces of 265 Wp Panels Total 15,900 Watt

MPPT 2 1 string of 20 pieces of 265 Wp Panels Total 5,300 Watt

The connected panels above are all same brand same type
I want to connect to the remaining 2 DC String connections

2 Strings of 16 panels each. Each panel 260 Watt

So one MPPT will operate with different strings. But each string exist out of the same panels.

Is that smart to do?

Curious to your answers

Kind regards

[Mike90250]

All the strings connected to a single MPPT input ( one or 3 connections, does not matter). If the strings are not matched equally, the MPPT will track the average of the lowest string,

[SupraLance]

What's the Vmp, Imp, Voc, Isc of the panels?
The way you propose to do it, the voltage of your single string of 265w pv will be pulled down to the Vmp of your 260w pv, lowering the output of that string.
What is the rated capacity of MPPT1? Any chance of moving your other 20 265w panels to it so each MPPT has only the 1 size of pv?
If not, what you propose is probably within the 5% tolerance, and depending how many watts you are losing, may be the most cost effective option.

[Bendesa1962]

Ok thanks for the answer Mike. I'm a bit confused. What exactly does that mean in this example? does it mean the MPPT will track on the lowest string in this case the 16 x 260 Watt. And it will loose the power of the extra watts in the string of 20 x 265 Watt? By the way I also asked GoodWe support about this question and they said it would not give any problems .....

[Bendesa1962]

Ok one more time the question with some more aditional info



They also have a GoodWe GW25K-DT installed with only 21,200 Watt connected

The GW25K-DT has 2 MPPT each MPPT can be connected to 3 strings

At the moment the GW25K-DT is connected to

4 strings of 20 panels each.

3 strings connected to MPPT 1
1 String connected to MPPT 2

Each panel is 265 Watt same brand

Voc 37,7V
Isc 9,29A
Vmp 30,7V
Imp 8,64A

MPPT 2 still has two DC string connections available.

Can I connect two extra strings to MPPT 2 with the following specs all same panels same brand

String 1 16 panels of 260 Watt each
String 2 16 panels of 260 Watt each

Voc 37,98V
Isc 9,04A
Vmp 30,63V
Imp 8,49A

All panels will be facing the same orientation and also have the same tilt.

[littleharbor]

I would take the total of 52 panels subtract one, and create 3 strings of 17 panels. You will lose a small amount of potential output due to the small panel mismatch but your voltage between strings will be much closer.

[Mike90250]

The string with the lowest voltage, limits the entire group on a single MPPT channel.
It won't cause a problem for the inverter, it don't care.
It will reduce your harvest by the amount of the mismatch. Your task is to shuffle things around to minimize the mismatch