Growatt 10kW SPH 10000TL String sizing

[Boisblancboy]

Hoping someone can help me with the math and string with this inverter.

So it’s has 3 MPPT’s and says 2 string per tracker. When utilizing 2 strings per tracker how do you design that? Would you have to add the VOC of each of those 2 strings together to make sure you don’t go over max voltage for that 1 mppt?

Sorry if this is a dumb question. I understand the sizing and math of small MPPT’s but not these larger units.

In my application I think I’d rather run things in series as I shouldn’t get much shading at all expect for morning and evening.

Thanks

 

[sunshine_eggo]

The three trackers are completely independent.

On each tracker, you can have up to two identical strings of panels in parallel.

The voltage of each string must be under 525Voc on your coldest day in the last 30 years.

The USABLE current on each tracker is 22A. If you have more than that, it will not be used.

The MAXIMUM Isc on the MPPT is 27A, so two strings in parallel must not exceed 27A. The concern is the MPPT could be damaged if your Isc is higher than 27A.

Example, my panels:

330W panel, 45Voc, 37Vmp, 8.9A Imp, 9.4A Isc

Provided it NEVER gets below -16°C (I approximated this), I could put a 10S2P array on each MPPT yielding:

450Voc at 25°C
370Vmp at 25°C
17.8A Imp at 25°C
18.8A Isc at 25°C

Thus I have met the following:

< 10,000W per MPPT
< 525V provided temperature is > -16°C
< 22A Imp
< 27A Isc

 

[Boisblancboy]

View attachment 271671

The three trackers are completely independent.

On each tracker, you can have up to two identical strings of panels in parallel.

The voltage of each string must be under 525Voc on your coldest day in the last 30 years.

The USABLE current on each tracker is 22A. If you have more than that, it will not be used.

The MAXIMUM Isc on the MPPT is 27A, so two strings in parallel must not exceed 27A. The concern is the MPPT could be damaged if your Isc is higher than 27A.

Example, my panels:

330W panel, 45Voc, 37Vmp, 8.9A Imp, 9.4A Isc

Provided it NEVER gets below -16°C (I approximated this), I could put a 10S2P array on each MPPT yielding:

450Voc at 25°C
370Vmp at 25°C
17.8A Imp at 25°C
18.8A Isc at 25°C

Thus I have met the following:

< 10,000W per MPPT
< 525V provided temperature is > -16°C
< 22A Imp
< 27A Isc

Great that makes perfect sense, thank you!

Now would I combine the wiring of those two strings at the PV panels, thus having 1 run to the inverter?

Any other strings would then be connected to the one or both of the other MPPT’s, with all strings or incoming wattage to the MPPT’s not exceeding 15000W’s correct?

 

[sunshine_eggo]

Great that makes perfect sense, thank you!

Now would I combine the wiring of those two strings at the PV panels, thus having 1 run to the inverter?

Yes. Simply parallel them with MC4 parallel connectors and run a single wire pair to the MPPT input.

Any other strings would then be connected to the one or both of the other MPPT’s, with all strings or incoming wattage to the MPPT’s not exceeding 15000W’s correct?

correct.

In my example, if I did 10S2P each MPPT would have 6660W on it, which exceeds the 15,000W limit. A 7S2P array would be 4620W each, and would meet the requirement.

You also do not need to use all three MPPT. Assuming the 200A charge limit can be supplied purely by PV, you're limited to about 200A * 55..2V = 11,040W, so it can't use more than this.

 

[Boisblancboy]

Yes. Simply parallel them with MC4 parallel connectors and run a single wire pair to the MPPT input.



correct.

In my example, if I did 10S2P each MPPT would have 6660W on it, which exceeds the 15,000W limit. A 7S2P array would be 4620W each, and would meet the requirement.

You also do not need to use all three MPPT. Assuming the 200A charge limit can be supplied purely by PV, you're limited to about 200A * 55..2V = 11,040W, so it can't use more than this.

Thanks again. Your explanation was easy to understand for a layman like myself, much appreciated.

 

[mciholas]

Yes. Simply parallel them with MC4 parallel connectors and run a single wire pair to the MPPT input.

Electrically, yes, but for best performance, the two strings that are parallel should have the same sun exposure. The MPPT will operate at only one point and if the two strings have different exposure (angle, azimuth, shading), then the power output will be suboptimal.

This can matter a lot for, say, a roof mount with east and west roof planes. You want all the panels on one MPPT to be on one plane. For something like a ground mount with clear view, all the panels have the same exposure so every string works with any other.

Mike C.

 

[Boisblancboy]

Electrically, yes, but for best performance, the two strings that are parallel should have the same sun exposure. The MPPT will operate at only one point and if the two string have different exposure (angle, azimuth, shading), ten the power output will be suboptimal.

This can matter a lot for, say, a roof mount with east and west roof planes. You want all the panels on one MPPT to be on one plane. For something like a ground mount with clear view, all the panels have the same exposure so every string works with any other.

Mike C.

Makes sense, in my application it would be a ground mount all facing the same way, etc.

 

[sunshine_eggo]

Electrically, yes, but for best performance, the two strings that are parallel should have the same sun exposure. The MPPT will operate at only one point and if the two string have different exposure (angle, azimuth, shading), ten the power output will be suboptimal.

This can matter a lot for, say, a roof mount with east and west roof planes. You want all the panels on one MPPT to be on one plane. For something like a ground mount with clear view, all the panels have the same exposure so every string works with any other.

Mike C.

Where are you getting this? Two parallel strings with each individual string having common facing will not perform differently than with each string on a separate controller.

 

[mciholas]

Two parallel strings with each individual string having common facing will not perform differently than with each string on a separate controller.

Is that not exactly what I wrote?

The benefit of the two MPPT, one for each string, is that it is more fault tolerant. A busted or obscured panel in the parallel wiring takes out more power than in the separate MPPT wiring. Assuming all panels are working, well matched, same exposure, and within MPPT limits, parallel to one MPPT should be the same performance as two MPPTs.

If you aren't short of MPPTs, it is always better to use separate MPPTs for each string.

Mike C.

 

[GlenB]

If you have 3 total strings, run each to a separate input. Running two identical strings in parallel to one of the
3 PV inputs, shorts them together as far as I can tell. Parallel identical strings are never identical (shading, angle,
the strange whims of nature, etc)
My older inverters either have one or at most two MPP channels...I really dislike that feature.