Adding more panels to our current string

[Dokasrf]

Hello,

I have an ongoing project I posted here.

We already have 4 x 400W panels in the rooftop of our warehouse that brings down up to 1600 Watts and 110V.

The inverter we are about to purchase (SUN-10K-SG02LP1-EU-AM3) has this specs for the PV string:

PV String Input Data

Max DC Input Power (W): 15000

Max DC Input Voltage (V): 500

Start-up Voltage (V): 125

MPPT Voltage Range (V): 150-425

Rated DC Input Voltage (V): 370

Max. Operating PV Input Current (A): 26+26+26

Max. Input Short-Circuit Current (A): 44+44+44

No. of MPP Trackers/No. of String Per MPP Tracker: 3/2+2+2

It says startup 125 but we only have 110V. Long story short… We are adding a few more panels.


The panel I have chosen to add to the string is a 580W panel with these specs:

Electrical parameters at standard test conditions (STC: AM=1.5, 1000W/m2, Cells Temperature 25°C):

Typical Type: 580W

Max Power (Pmax): 580W

Max Power voltage (Vmp): 42.56V

Max Power current (Imp): 13.63A

Open circuit voltage (Voc): 51.43V

Short circuit current (Isc): 14.34A

Module Efficiency: 22.44%

Max system voltage: DC 1500V (TUV, UL) / 1000V (CUL)

Maximum Series Fuse Rating: 25A


And the specs of the ecoflow panels are these (If I am not mistaking):

Rated Power 400W (±3%)

Open Circuit Voltage 37.10V (±3%)

Short Circuit Current 13.79A (±5%)

Maximum Operating Voltage 31.00V

Maximum Operating Current 12.90A

Maximum System Voltage 1500V

Maximum Fuse Current 25A



I wanted to ask if these panels can work together or if it’s going to blow up when connected in series.


PS: I am not going to install them myself. I will have a professional installer hired but I need to make the research here and have all the tools ready for him.


Thank you!

 

[jgh]

You don't say how many you want to add.

Assuming you're adding in series with the existing string, that will be fine SO LONG AS the total voltage stays below your inverter's 500V max. The currents are close enough. Voltages just add up along the string. However, be aware that a panel output voltage varies with temperature, going up when it is cold. The standard conditions are 25 deg. Celcius; the panel specs should include a coefficient for voltage vs. temperature change. Work it out for the lowest historic temperature at your location.

 

[Dokasrf]

Thanks for replying.

Sorry I forgot to mention. I will add from 1 to 6 panels. Depends on a ton of things. There is a story behind the building I live that has to do with hereditary problems so I won't go into the story.

that will be fine SO LONG AS the total voltage stays below your inverter's 500V max.

I understand that part.

Panels in yellow. (image bellow you can see my panels. There are 4.). One panel on the left of the current string and 4 or 5 above with a special extension construction on the rooftop. Either wood or steel. I am going to be talking to builder as a research and find the best solution. My biggest concern is if it's going to have some voltage / power "more than MAX" going though a panel. That "open circuit" scares me. So could they work in series? Maybe we will make them 2 string setup I don't know..

 

[Hedges]

Open circuit voltage (Voc): 51.43V x 4
+
Open Circuit Voltage 37.10V (±3%) x [1 ... 6]
=
435V or less (at +3%)

500V / 435V = 1.15, +15% above nominal for cold

You didn't provide temperature coefficient of Voc from data sheet, or your location's record coldest temperature, but I expect it to not exceed +15% so you should be OK.

 

[DougL]

Maybe a better option would be to create 2 parallel strings. Make the lower rack one string and the new upper rack the 2nd string.
Equalize your voltages by putting 2 of your current 4 on the upper rack/string. So either 2 strings of 5 panels each(2 old+3 new) or 2 strings of 4 panels each( 2 old + 2 new ) so that you keep below the 500V max string voltage limit.
You can also look in your inverter operation manual what happens if you go over the max input voltage. Some inverters can handle much higher voltage than the max and what they do is MPPT limits the string voltage down to the 'operating' max input voltage. Others say DO NOT go above max input voltage.

 

[Hedges]

"MPPT Voltage Range (V): 150-425

Rated DC Input Voltage (V): 370

Max. Operating PV Input Current (A): 26+26+26

Max. Input Short-Circuit Current (A): 44+44+44

No. of MPP Trackers/No. of String Per MPP Tracker: 3/2+2+2

It says startup 125 but we only have 110V. Long story short… We are adding a few more panels."

Could be two strings, not parallel but each on its own MPPT. 3 strings supported.

Likely 370Vmp is optimum. Your 4s + 6s = 10s (heterogenous) is 362V nominal, so I'd say do one string as you plan.

 

[Dokasrf]

We have some changes in the plan. We are thinking about

1. A new string for the DEYE Inverter that will be setup on top of the main house rooftop made of 8 panels*415W=3.320W (41.83V * 8 = 334,64V)

and

2A. Keep the old Ecoflow string just for ecoflow recharging so we won't mess with the new string
or
2B. Use a step up in the current string to go over the 150V to use it as a second MMPT.

We will see what we'll do because of the voltage limitation of the inverter to 500V.


I don't want to bother the forum with a new thread so please if you don't mind me asking here.

Something about the specs of the inverter please:

Max DC Input Voltage (V): 500 So this is the MAX Voltage from all the strings combined. Right?

Start-up Voltage (V): 125 If the string is bellow that voltage it won't register to the inverter. Right?

MPPT Voltage Range (V): 150-425 If the MAX Voltage is 500, how is this 425? If the startup is 125 why is this 150?

Rated DC Input Voltage (V): 370 Is this the "preferred by the manufacturer voltage" if we can say so?

 

[DougL]

We have some changes in the plan. We are thinking about

1. A new string for the DEYE Inverter that will be setup on top of the main house rooftop made of 8 panels*415W=3.320W (41.83V * 8 = 334,64V)

and

2A. Keep the old Ecoflow string just for ecoflow recharging so we won't mess with the new string
or
2B. Use a step up in the current string to go over the 150V to use it as a second MMPT.

We will see what we'll do because of the voltage limitation of the inverter to 500V.


I don't want to bother the forum with a new thread so please if you don't mind me asking here.

Something about the specs of the inverter please:

Max DC Input Voltage (V): 500 So this is the MAX Voltage from all the strings combined. Right?

Start-up Voltage (V): 125 If the string is bellow that voltage it won't register to the inverter. Right?

MPPT Voltage Range (V): 150-425 If the MAX Voltage is 500, how is this 425? If the startup is 125 why is this 150?

Rated DC Input Voltage (V): 370 Is this the "preferred by the manufacturer voltage" if we can say so?

It should be Max DC input voltage on each MPPT, not combined MPPT inputs as long you you have multiple MPPT circuits and not just multiple connections into one MPPT circuit.
Startup PV voltage is around when the inverter will start but it often will start around that voltage, pulll down the voltage, shut off for a bit then start again. Just not going to get much power down at that low voltage.
They pick the MPPT range as where it'll operate well and produce decent power. vague I know but it seems to be where things work well and they will pick those such that people don't think going to the high end is OK only to realize when it gets cold those voltage jump up well over the voltages when hot.
Ideal input range of 370V is just so you stay above the low operating voltage when panels are hot and below the max voltage when cold. Some areas don't get below 40 degF, some go below zero F, some don't go above 90F and others go above 120F. So they really can't provide numbers for every situation.