Growatt SPH10000TL-HU-US question

[diWhy]

Fired up mine a couple of weeks ago and while support is helpful, they do not provide technical information that goes beyond normal usage.
Sometimes, they are simply not sure so this is not a complaint about them, just asking since there are folks here that have learned beyond the manual shall we say.

I notice something that may or may not be odd. I have two strings of 21 panels each. These should generate up to just under 10KW once I'm connected to the grid. Right now, I'm using it off-grid until all the permits/approvals etc are completed. This means I've got it connected to grid but set in self consumption mode only.

Most of the load is handled by one MPPT only, the other is always much lower in wattage usage. Is this normal?
Does the inverter try to balance the PV usage of does it simply use the first string and a little of the second string and as needed, pulls more from the PV.

Thanks.

 

[gbaig]

Great product, but their technical teams lack knowledge. I was struggling to get configuration for "time of use". failed to get any support. So much so, I have written to Growatt Australia, UK, South Africa, and US but Zero support. I was able to get the desired results from other manufacturers of solar inverters, as TOU is a standard feature.

 

[1201]

Great product, but their technical teams lack knowledge. I was struggling to get configuration for "time of use". failed to get any support. So much so, I have written to Growatt Australia, UK, South Africa, and US but Zero support. I was able to get the desired results from other manufacturers of solar inverters, as TOU is a standard feature.

Do you mind sharing a screenshot of how yours is setup, with a small writeup, to help others in the future.

Thanks!

 

[mciholas]

I have two strings of 21 panels each.

Spec sheet on the SPH 10000TL-HU-US says this:

Max DC voltage 525V

MPPT voltage range 150-450V

Your highest panel Voc would have to be under 25 volts and your highest panel Vmp would have to be under 21.4 volts to meet the above limits with 21 panels in series. Those are low voltages for typical panels used in such a system. 21 panels in a string seems like an usually large number to me.

Are you sure you haven't exceeded the maximum voltage levels of the system? Maybe one MPPT is busted and that's why you get all the power from the other.

The inverter has a PV over volt warning code, W83 or F40, are you not getting one of those?

What panels are you using, exactly?

Mike C.

 

[gbaig]

Do you mind sharing a screenshot of how yours is setup, with a small writeup, to help others in the future.

Thanks!

1. Settings —> Operating Modes—> Select consumption—> check PV sell in case you have net metering—>go down and check Time of use.—> select the time you want to switch from grid to battery—> End time—> you must select battery % so that inverter keep discharging it till your desired percentage before cutting it off.—> I have left rest at 100% as I don’t want to switch grid to the battery. Since I have battery first, next day battery is recharged to 100% first before moving solar to load and grid export.

 

[diWhy]

Spec sheet on the SPH 10000TL-HU-US says this:
Max DC voltage 525V
MPPT voltage range 150-450V
Your highest panel Voc would have to be under 25 volts and your highest panel Vmp would have to be under 21.4 volts to meet the above limits with 21 panels in series. Those are low voltages for typical panels used in such a system. 21 panels in a string seems like an usually large number to me.
Are you sure you haven't exceeded the maximum voltage levels of the system? Maybe one MPPT is busted and that's why you get all the power from the other.
The inverter has a PV over volt warning code, W83 or F40, are you not getting one of those?
What panels are you using, exactly?

I'll add more context and the notes I've kept.
Growatt SPH10000TL-HU-US
Panels are older Mage / Powetec Plus, 250 / 6 PL US AC.
I don't see any warnings. I was in touch with self2solar techs with my config before wiring it up and they said it would be fine.
However, the electrician that's drawing up the diagram for the city thinks I should re-wire the panels into three inputs.

Inverter Specifications (Growatt SPH 10000TL-HU-US)
Specification Value
Maximum AC Output Power 10,000W
MPPT Inputs 3 MPPTs
MPPT Inputs in Use 2 MPPTs
Maximum DC Input Power 15,000W
Maximum Input per MPPT 10,000W
MPPT Input Voltage Range 150V - 1000V
Startup Voltage 150V
MPPT Maximum Current 22A per MPPT

Each canopy consists of 21 panels, totaling 42 panels in the system.
Panel Specification Value
Nominal Voltage (Vmp) 32V
Nominal Current (Imp) 7A
Maximum Power Output (Pmp) 238W per panel
Open Circuit Voltage (Voc) 42V (varies with temperature)
Short Circuit Current (Isc) 8A (max observed under ideal conditions)

String Configuration per Canopy
Each MPPT receives 3 strings of 7 panels in series
Each string consists of:
Voltage (Vmp per string): 32V×7=224V32V×7=224V
Current (Imp per string): 7A7A
Each MPPT receives:
Total Voltage: 224V (nominal)
Total Current: 3×7A=21A3×7A=21A
Total Power: 224V×21A=4,704W224V×21A=4,704W

MPPT Inputs & Power Distribution
MPPT Strings Connected Voltage (Vmp) Current (Imp) Power (Wmp)
MPPT 1 3 Strings (7 panels each) 224V 21A 4,704W
MPPT 2 3 Strings (7 panels each) 224V 21A 4,704W

Total Power Input to the Inverter: 9,408W
Total Current per MPPT: 21A (staying within the 22A max limit)

Open Circuit Voltage (Voc) Considerations
Observed
Some strings show up to ~300V open circuit voltage
Other strings show around 225V open circuit voltage

Expected Voc Calculation
Voc per panel: 42V
Voc per 7-panel string: 42V×7=294V42V×7=294V
Real-world variation: Can fluctuate depending on temperature and panel conditions.

Impact of Voc on System Performance
Under full sun, operating voltage should settle around ~224V per string.
Open circuit testing shows higher values (near 300V), which is normal.
Lower observed values (225V) indicate potential panel issues, shading, or wiring losses.
System must stay above 150V startup voltage to function correctly.

System is Well Within MPPT and Inverter Limits
Max Current per MPPT: 21A (Safe, below 22A max)
Max Voltage per MPPT: 224V operating, ~300V Voc (Safe, below 1000V max)

 

[mciholas]

However, the electrician that's drawing up the diagram for the city thinks I should re-wire the panels into three inputs.

It will perform better if the PV inputs are around 360 volts.

Inverter Specifications (Growatt SPH 10000TL-HU-US)
...
MPPT Input Voltage Range 150V - 1000V

The data sheet I see says 525 volts.

https://us.growatt.com/upload/file/SPH_10000TL-HU-US_Datasheet_EN_202406.pdf

1000 volts looks well over the max (525 volts) and over the MPPT range (150 to 450 volts).

A string of 21 panels could be almost 900 volts, WAY over the MPPT limits.

MPPT Inputs & Power Distribution
MPPT Strings Connected Voltage (Vmp) Current (Imp) Power (Wmp)
MPPT 1 3 Strings (7 panels each) 224V 21A 4,704W
MPPT 2 3 Strings (7 panels each) 224V 21A 4,704W

So do you have strings of 21 or strings of 7?

If 7 strings, that's entirely different.

If you have 21 panels, you would be better off with 2 strings of 10 and 11 (on different MPPTs) to get closer to 360 volts than 7.

Mike C.

 

[diWhy]

Two canopies, each with 21 panels. Each canopy is 3 strings of 7 panels.
1000 is a typo.

>If you have 21 panels, you would be better off with 2 strings of 10 and 11 (on different MPPTs) to get closer to 360 volts than 7.
I'm being told by the person doing the diagram that I should lower the number of panels to get to three MPPT inputs instead of two.

 

[kscessnadriver]

I'm not sure that 2 versus 3 MPPTs makes much of a difference. I doubt you're over-powering the MPPT's as it is. If you've got voltage differences on otherwise similarly oriented strings, with the same panels, I'd be looking at wiring issues or panels that are busted.

In your case, with a single SPH, and 42 panels, I'd probably set it up with 4 strings of 10. Forget 42, just use 40. Bring each string of 10 into the inverter on its own wire, and you can parallel 2 strings that have the same orientation when you connect them to the inverter (each MPPT has 2 inputs on this inverter. Or if you've already got the wires, parallel 2 at the array, and just run 3 circuits to the inverter.

 

[diWhy]

I'll have to do that again when it warms up. I don't recall anything obvious when checking all of the strings but something is not right.

 

[kscessnadriver]

I've been running mine off grid, with minimal loads on them at this time. I'm just about done with the full grid tie install, so then I'll really be able to see how well these work.

 

[diWhy]

Me too, IF I ever get past the red tape. I bought a couple of RUiXU batteries as well which I'd like to try at some point.

 

[kscessnadriver]

Me too, IF I ever get past the red tape. I bought a couple of RUiXU batteries as well which I'd like to try at some point.

I've got 6 Ruixu server rack batteries running for now. Once the install is complete, I've got a bunch of batteries to add later, I've got 100+ kWh of Sunvault batteries sitting, that I'm planning on installing.

 

[mciholas]

Two canopies, each with 21 panels. Each canopy is 3 strings of 7 panels.

Makes more sense now, at max power, this is 224 volts. I was responding to your statement earlier "I have two strings of 21 panels each." which left me concerned.

I'm being told by the person doing the diagram that I should lower the number of panels to get to three MPPT inputs instead of two.

The MPPTs have to boost to about 360 volts to make AC output. The closer you get to that voltage, the more efficient it will operate.

10 panels is 320 volts, 11 is 352 volts. That will work better than 3 strings of 7 boosting from 224 volts to 360 volts. The performance gain could be about 3-4% with the change.

The 10 + 11 plan has to use different MPPTs for each string due to the different voltage.

Mike C.

 

[diWhy]

My bad for not having the lingo down quite yet .
It was mentioned that going with 10/11 panels might be better but that would make 4 outputs total and the inverter only has three at 21A max.
I know each MPPT is dual but not really sure what that means.

Guess I have to start calculating again then.

 

[mciholas]

It was mentioned that going with 10/11 panels might be better but that would make 4 outputs total and the inverter only has three at 21A max.

Okay, I see now.

You presently have two MPPTs, each serving three strings in parallel of 7 panels each per canopy, and one MPPT left over. Is that right?

From your MPPT point of view, that's 224 volts and 21 amps per MPPT, based on Imp being 7 A and Vmp being 32 volts per panel.

Given that, I suspect you have the best layout you can do that doesn't require adding panels or massive rewiring of the array.

If you could add a panel to each canopy, 22 panels, and arrange them in 2 parallel strings of 11 each, that would make things better, and it still uses two MPPTs. I suspect you can't do that, so this won't work.

As to rewire with 3 inputs, if you made 3 MPPTs each take a string of 14 panels (you have to split wire 7 from one canopy and 7 form another), then you get a total Vmp of 448 volts, which is too much, so that doesn't work.

One option is to rewire the canopies to be 2 parallel strings of 10 panels, leaving one panel unused (future backup). This reduces your active array to 40 panels from 42, a loss of 5%, which is likely worse than what you have now.

Given what I infer are the constraints, using two MPPTs, one for each canopy, serving 3 parallel strings of 7 panels is about as good as you are going to do.

Maybe you can find a place to throw up a few more panels on the MPPT you have left over.

As to your original question about uneven power, are the panels in full sun when this unevenness is noticed?

One thing to do would be to swap which is MPPT 1 and MPPT 2 at the inverter and see if the low power follows the MPPT or the array. If it is the MPPT, then maybe it is faulty, or maybe the inverter is programmed not to use more power than what one MPPT can provide.

If it follows the array, then you have a wiring problem to solve.

Mike C.

 

[diWhy]

I ended up re-configuring the setup because the amps were too high, not enough wiggle room.
I went with this. Much safer.