12kw Growatt panel questions

[Bravo4]

Hello all! New to posting but have been here several times to view threads. My question is about my options for panels as I was told by SS that the controllers have to have even paneling or result in clipping. My current set up is below. I am welcoming ideas to get better results with what I have as buying 4 more 355w panels is not easy, places want min orders. What I am seeing now is just before the peak the of the day the wattage is equalizing between them; from 2100w and 1750w to each giving 1350+/-. This will continue the rest of the day going up or down slightly until PV1 is shadded. Ideas are welcome. Thank you.

12kw Growatt 12000T dvm / this is the 150Voc per mppt
5 lifepower 51.2v batteries in parallel rack with 4/0 from bus to the inverter
PV1 - 12 Canadian Solar 300W Poly 72 Cell - 44.6 VOC - 8.87 Amp - 3 in serries 4 parallel = 133.8v x 33.2a x 3600w
PV2 - 6 REC 355W 144 Half Cell - 46.9 VOC - 9.09Amp - 2 in serries 3 parallel = 94v x 27.27a x 2130w

 

[Zwy]

If the mismatch is a problem and it is clipping PV input on the larger string, you do have the option of just adding another SCC and running one string thru it instead.

 

[sunshine_eggo]

PV1: 3600W
PV2: 2130W

I have no data to indicate whether what SS is saying is true or not. I would be surprised if it is, and it would be another tick mark in a box for why I don't like MPP Solar/Growatt units.

That said, the battery being in absorption/float mode puts an upper limit on the current (power) it will accept. When the current is limited, multiple charging sources may behave somewhat erratically as they respond to each other's influence on battery voltage.

In other words, array power is limited by what the battery will accept + loads.

I recommend that at peak solar, you deliberately engage a load/loads greater than 6000W total. Observe how the array's behave.

Note that 3S configuration with 72 cell panels on 150V MPPT leaves very little margin for cold temperature voltage increase and is rarely recommended. Anything below about 7°C runs the risk of your Voc exceeding 150V and damaging the MPPTs. You have a little more margin than that with the Canadian panels.

 

[Bravo4]

PV1: 3600W
PV2: 2130W

I have no data to indicate whether what SS is saying is true or not. I would be surprised if it is, and it would be another tick mark in a box for why I don't like MPP Solar/Growatt units.

That said, the battery being in absorption/float mode puts an upper limit on the current (power) it will accept. When the current is limited, multiple charging sources may behave somewhat erratically as they respond to each other's influence on battery voltage.

In other words, array power is limited by what the battery will accept + loads.

I recommend that at peak solar, you deliberately engage a load/loads greater than 6000W total. Observe how the array's behave.

Note that 3S configuration with 72 cell panels on 150V MPPT leaves very little margin for cold temperature voltage increase and is rarely recommended. Anything below about 7°C runs the risk of your Voc exceeding 150V and damaging the MPPTs. You have a little more margin than that with the Canadian panels.

Thanks for the reply. I was curious if that may have an effect on the input. I will load it up when we get sun again and let you know what I find.

Regarding your note. I did use the voltage calculator located here: https://gold-coast-solar-power-solutions.com.au/posts/solar-panel-maximum-voltage-calculator/. I got a total of 144v at expected lows in my area. Thats why I ran the Canadian Solars 3s and the REC 2s.

 

[sunshine_eggo]

Thanks for the reply. I was curious if that may have an effect on the input. I will load it up when we get sun again and let you know what I find.

Please do. This is a common issue when the battery can't accept the full power of the array when in absorption mode. A 6kW load will guarantee both MPPT need to put out their max output, and you'll see if one MPPT is limiting the other in some way.

Regarding your note. I did use the voltage calculator located here: https://gold-coast-solar-power-solutions.com.au/posts/solar-panel-maximum-voltage-calculator/. I got a total of 144v at expected lows in my area. Thats why I ran the Canadian Solars 3s and the REC 2s.

Good deal. I missed the 2S detail in the original post.

 

[Bravo4]

Update.
The charge controllers limit input according to SOC of the battery bank. Starting at 90% it limits input from arrays then again at 96% it halves the input again. At these points the input equalizes between the 2 PV inputs. When the SOC drops below 90% you then get full input again from the separate arrays. I do not see that the smaller array is clipping the larger array.

Thank you for your help.

 

[timselectric]

It's not an issue with 2 PV inputs.
They are independent of each other.

 

[Bravo4]

It's not an issue with 2 PV inputs.
They are independent of each other.

I thought that was the case but was told by SS that they are on the same BUS/Board one would clip the other.

 

[timselectric]

Is it 2 inputs for a single MPPT?
If so, then yes.

 

[kromc5]

Hello all! New to posting but have been here several times to view threads. My question is about my options for panels as I was told by SS that the controllers have to have even paneling or result in clipping. My current set up is below. I am welcoming ideas to get better results with what I have as buying 4 more 355w panels is not easy, places want min orders. What I am seeing now is just before the peak the of the day the wattage is equalizing between them; from 2100w and 1750w to each giving 1350+/-. This will continue the rest of the day going up or down slightly until PV1 is shadded. Ideas are welcome. Thank you.

12kw Growatt 12000T dvm / this is the 150Voc per mppt
5 lifepower 51.2v batteries in parallel rack with 4/0 from bus to the inverter
PV1 - 12 Canadian Solar 300W Poly 72 Cell - 44.6 VOC - 8.87 Amp - 3 in serries 4 parallel = 133.8v x 33.2a x 3600w
PV2 - 6 REC 355W 144 Half Cell - 46.9 VOC - 9.09Amp - 2 in serries 3 parallel = 94v x 27.27a x 2130w

I'm not sure of how your panels will behave in cold but you can calculate it. If you do have some really cold days with sun you can get up the limit quickly. I went through so many issues my two 150v 12kw growatts inverters. I had to stop using the pv inputs and switch over to all sccs. I was told to wire the 2s but the 150v will not run on those but 3s with cold put me too high. I would really monitor them as the 12kw 150v will not warn you if it gets high. If you do not want to buy more panels you could by a growatt 250v scc, move pv1 over to make sure your inverter stays safe.

 

[Bravo4]

Is it 2 inputs for a single MPPT?
If so, then yes.

There are 2 separate mppts.

I'm not sure of how your panels will behave in cold but you can calculate it. If you do have some really cold days with sun you can get up the limit quickly. I went through so many issues my two 150v 12kw growatts inverters. I had to stop using the pv inputs and switch over to all sccs. I was told to wire the 2s but the 150v will not run on those but 3s with cold put me too high. I would really monitor them as the 12kw 150v will not warn you if it gets high. If you do not want to buy more panels you could by a growatt 250v scc, move pv1 over to make sure your inverter stays safe.

Thanks. I did calculate for -10f. We have had some sunny days in the teens and not come close since the install so I am continuing to monitor. I was looking at the 250v Growatt originally but they sold out the day I was making the purchase.

 

[timselectric]

There are 2 separate mppts.

Then, there's no issue.
They are independent of each other.
And of course they output to a common DC bus.
All SCC's in a system do.
It's called a "battery".

 

[Zwy]

Then, there's no issue.
They are independent of each other.
And of course they output to a common DC bus.
All SCC's in a system do.
It's called a "battery".

Sounds like Sig Solar likes creating myths?

Can't be. LOL

 

[kromc5]

There are 2 separate mppts.

Thanks. I did calculate for -10f. We have had some sunny days in the teens and not come close since the install so I am continuing to monitor. I was looking at the 250v Growatt originally but they sold out the day I was making the purchase.

Maybe about a month after I bought the second 150v they came out with the 250v. It would of saved me a small fortune on wiring if and sccs if I could have gone with those first.

 

[timselectric]

Yup
High voltage MPPT, was a big selling point for my selection.

 

[Zwy]

Maybe about a month after I bought the second 150v they came out with the 250v. It would of saved me a small fortune on wiring if and sccs if I could have gone with those first.

Are you running with 2 parallel PV strings Y'ed together at array, then splitting it to each SCC?

 

[kromc5]

Are you running with 2 parallel PV strings Y'ed together at array, then splitting it to each SCC?

I have 6 sccs up and running with two more on the way. I have a mix of 18/15 panels arrays that paralleled and then y'ed into both inputs on each scc.

 

[timselectric]

Not going through this, again.
I'm out. lol

 

[Zwy]

Not going through this, again.
I'm out. lol

I hadn't heard of an update since he started using the Y'ed SCC inputs. kromc5 hasn't been on lately, I'm curious how it is working out. Too many naysayers, yet he has been running this setup.

I have 6 sccs up and running with two more on the way. I have a mix of 18/15 panels arrays that paralleled and then y'ed into both inputs on each scc.

Do the MPPT's split the amps? Have you seen any problems with this as many claim the 2 MPPT's would constantly be looking for the maximum power point and fight each other to achieve it?

 

[timselectric]

I hadn't heard of an update since he started using the Y'ed SCC inputs. kromc5 hasn't been on lately, I'm curious how it is working out. Too many naysayers, yet he has been running this setup.

I can only assume that the only reason that it's working is because the MPPT's aren't fully separated, internally. Which would also explain Signature Solar's response to the OP, in this situation.