Growatt 12kw 250, Over Paneling and Uneven Sting Count

[MrM1]

Planning to buy a Growatt SPF 48vdc 12kw 250. Already talked to Watts247 asked about over paneling. Said you can over panel the spf 12kw inverter / SCC.

Real Estate does not matter. The array is going in a 10 acre pasture field

The Growatt Manual says 7000w array and a max of 250vdc. Watts247 noted that I can use a larger array but the Growatt will only use 7000 watts and produce no more than 120a charge current at 48vdc system.

1st question. The Growatt spf 12kw 250 has 2 PV inputs for the solar charge controller (SCC) . Does That mean that each input takes 250vdc each... OR... does each input only take 125vdc each for a total of 250vdc

2nd question...
So our plan was to get 24 440w panels. VOC 193 / ISC each string 11. 5a x 6 = 69 amps. Growatt spf 12kw has 2 PV inputs so 34.5 amps each input.

Yeah, way over paneled, but does it matter? I'm planning for clouds and extra morning/afternoon generation. And planned to orient 2 of the 6 stings in different directions. 4 stings S, 1 SE and 1SW. If I'm wasting too much power from the array and we need it, I'd buy a second SCC.

BUT...

Can't find any 440w panels now. But found a deal on 370w panels.

28 panels gets me back up to the array size of the 440w panels. The ISC and VOC of the 370w panels are similar to (less than) the 440w panels so no problem there.

Problem is... Now I would have 7 stings and not 6 stings. 4 stings and 44amps on 1 pv input, and 3 stings 33 amps on the other pv input of the Growatt. Everything would still be under 200 vdc. 194vdc on pc1 and 194 vdc on pv 2.

Will this be a problem? Or should I add 4 more panels, 1 more sting to the smaller side to balance them out?

That would make the array 32 panels, 8 4s stings and a total of 11,840 watts 6 stings S, 1 string SE, 1 string SW.

Thoughts?

Thanks @tweekzilla @kromc5
@Hedges

 

[DThames]

Available power on two different PV inputs shouldn't matter. I would say that if you have some strings facing a different direction and on the same charger input, that you will see lower peak amps than when they all face the same way. That is a given. But here is something to ponder....in the event you wonder, is this string preforming as expected, you will not be able to look at the charger and determine much, with different facing strings. You would be able to measure the amps on a given string and see if the amps on that string were up to par. But if the entire array was swamping the one PV charger input with power, the charger would be maxed out and you couldn't measure one string, unless you removed some of the other strings to get the power below max. Just a thought.

Also, while the charger should be designed to handle its rated load, if I had one that I planned to max out for more than a couple hours a day (like you might with different facing strings and major over paneling) I would be sure to look at improving the airflow over the charger. Maybe an extra fan to help carry away some heat. Make sure nothing could hamper the airflow around the unit, etc.

 

[RobertGreen]

as for your 1st question: each PV input can be 250v max (it's not 125v each)
Be careful; the manual and specifications listed on the watts247 is not for the correct model. Here's a link to the manufacturer:

Growatt

 

[MrM1]

But if the entire array was swamping the one PV charger input with power, the charger would be maxed out and you couldn't measure one string, unless you removed some of the other strings to get the power below max. Just a thought

@DThames So I wouldn't be able to tell if the array was actually preforming at its rated power? Not a problem if it's keeping up.

And great idea on the fan. I will do that. But I have a midnite solar classic 150 over paneled in a different location. Midnite solar tech support told me the classic just wouldn't use the extra power and wouldn't dissipate it as heat. Hopefully the Growatt scc of the spf 12kw will do the same.

 

[RobertGreen]

I can't determine this from the growatt documentation, but I strongly suspect that each PV input will be limited at half the total charging current. In other words, with separately facing arrays, you won't get more than 3500w charging power from a given input at a time no matter how it's overpaneled.

 

[MrM1]

as for your 1st question: each PV input can be 250v max (it's not 125v each)
Be careful; the manual and specifications listed on the watts247 is not for the correct model. Here's a link to the manufacturer:

Growatt

Are you saying the specs listed on the watts247.com site for the Growatt 250V Dual PV Input – 48V 12000T MPV 12kW are not correct?

I did actually write them about the inverter and they responded to back it was OK to Overpanel. Just don't know how much.

Why would Overpaneling matter if I stay at 200 vdc input? Wouldn't any extra just go unused?

​

 

[MrM1]

I can't determine this from the growatt documentation, but I strongly suspect that each PV input will be limited at half the total charging current. In other words, with separately facing arrays, you won't get more than 3500w charging power from a given input at a time no matter how it's overpaneled.

Yes That is what I think each input only puts out 60 amp charging.

 

[RobertGreen]

Are you saying the specs listed on the watts247.com site for the Growatt 250V Dual PV Input – 48V 12000T MPV 12kW are not correct?

Yes, that's what I am saying. If you're looking at this link: https://watts247.com/product/new-gr...se-120v-240v-output-100a-at-120v-50a-at-240v/

The specifications shown on that page, and the manual.pdf file listed are for the wrong model: the 12000T DVM series rather than MPV series.
Here's a link to the manual for the 12000T MPV series: https://www.growatt-america.com/upload/file/contents/2021/03/60618dc3c474c.pdf

 

[MrM1]

@stienman I have seen on other threads here u have talked some about this

 

[DThames]

@DThames So I wouldn't be able to tell if the array was actually preforming at its rated power? Not a problem if it's keeping up.

And great idea on the fan. I will do that. But I have a midnite solar classic 150 over paneled in a different location. Midnite solar tech support told me the classic just wouldn't use the extra power and wouldn't dissipate it as heat. Hopefully the Growatt scc of the spf 12kw will do the same.

"Midnite solar tech support told me the classic just wouldn't use the extra power and wouldn't dissipate it as heat." ......that should be 100% true for every charger on the market. The charger will only charge at the rated amps. There is no other "power" there unless you create a load for it, like a second charger. What is done with potential power is not what I am talking about.

If any power device runs at 100% rating, you would expect it to make more heat than if it was running at 70% of its rating. Even slightly over paneled, an array facing one direction will get full power only about 2 hours a day. So the charger would be at 100% rated for only a couple of hours....hopefully for any number of hours. But if it was designed "on the edge" and would tolerate 100% for only about 2 hours and be over the edge after 2.5 hours then that would be okay for most setups (even still). But as you described, you might be maxed out for 5 or 6 hours. Still a proper designed unit should be just fine if nothing is wrong, if the room is not warmer than normal, mud wasps haven't built nests in the cooling fins, etc. Extra cooling might give a fee;omg of "I have done what I can to ensure it has good air".

I work in the industrial electric motor business. Most motors running at full rated load are so hot you can't keep your bare hand on them. This heat will (after years) degrade the internal insulation. If you put that motor in a warm environment, or restrict the airflow so the temp goes up even a little, the damage is accelerated. We produce "damage curves" so customers can see what harm they do to the motor life if they let it get warmer than what the design is based for. In some cases that damage is just the cost of running an oven or something else hot and can't be avoided. But if you can help control the heat, your electronics might last a bit longer.

 

[MrM1]

@DThames great answer

In the classic I can limit max amps. On my classic I also have a 4" fan on it thru the day on a timer and it's on a 1" heat sink.

I have no idea if the growatt has a max charge current limiter. But fans I can do

 

[stienman]

tl;dr:
1) The Growatt SPF 12000T DVM-MPV has two 250V max VOC charge controllers. Your target of 200VOC is perfect.
2) Each string can be different, you don't need to match them, just don't go over 250VOC on either one.
3) The charge controller does not use "excess" energy. Once it hits the maximum charge current it simply doesn't convert/consume more. The solar panels will raise their voltage until the current and voltage match the consumption.
4) The maximum charge current is 60A, which means that you'll likely only pull 3.2kw unless your battery operates around 58v
5) The Growatt can limit charge current from the solar array.
6) It has fans. Loud, high CFM fans. You really don't need additional cooling unless its environment is above 40C (104F).


The growatt SPF 12000T DVM-MPV has two separate charge controllers, and you can think of them as completely independent of each other and the rest of the unit. Each one is rated for 250 max VOC input and will not convert more than 3,500W from the array - however they will also not convert more than 60A per charge controller to the battery bank, meaning that you'll typically only get 3kw from each one unless your battery bank goes up to 59v. I'll continue to refer to the maximum 3.5kw, though. You can add millions of panels to each one and as long as they never go over 250V the charge controllers will take as much as they can - up to 3.5kw - and push it into the batteries, while also following the battery settings.

Over paneling is no problem.

The reason there are two chargers is so you can optimize your arrays and get the most energy from them that is available at any given time. This will only matter if your arrays are producing under 3.5kw each - in that case the charge controller will adjust its draw to maximize the power coming from the array. If your arrays are pointing different directions, or consist of different panels, or different number of strings, then there will be times when maximizing one means a higher voltage, while the other will have maximum power at a lower voltage. Putting them all on one input, in those cases, would be less efficient, but never dangerous or damaging.

So having the two arrays with different string counts isn't going to hurt anything. Worst case you'll know that at a certain time of day the array with more panels will be producing over 3.5kw, some of it wasted, and the other array less than 3.5kw, with some of the charge controller capacity wasted. Since you're overpaneling on purpose, I doubt this really matters much to you.

The charge controller on the Growatt is a little odd. You have only two current limiting settings: Maximum charge current (regardless of source) and AC charge current (only from the AC/generator input). If you have no AC input, then the first is effectively the solar charge current limiter. If you have AC input then maximum solar charge current will depend on other settings, such as source prioritization, battery status, etc.

In your case it shouldn't matter - you're overpaneling, so just set it to the maximum current your battery bank can handle and call it a day, and if needed set the AC current so it doesn't draw more than the AC input circuit is capable of.

 

[MrM1]

tl;dr:
1) The Growatt SPF 12000T DVM-MPV has two 250V max VOC charge controllers. Your target of 200VOC is perfect.
2) Each string can be different, you don't need to match them, just don't go over 250VOC on either one.
3) The charge controller does not use "excess" energy. Once it hits the maximum charge current it simply doesn't convert/consume more. The solar panels will raise their voltage until the current and voltage match the consumption.
4) The maximum charge current is 60A, which means that you'll likely only pull 3.2kw unless your battery operates around 58v
5) The Growatt can limit charge current from the solar array.
6) It has fans. Loud, high CFM fans. You really don't need additional cooling unless its environment is above 40C (104F).


The growatt SPF 12000T DVM-MPV has two separate charge controllers, and you can think of them as completely independent of each other and the rest of the unit. Each one is rated for 250 max VOC input and will not convert more than 3,500W from the array - however they will also not convert more than 60A per charge controller to the battery bank, meaning that you'll typically only get 3kw from each one unless your battery bank goes up to 59v. I'll continue to refer to the maximum 3.5kw, though. You can add millions of panels to each one and as long as they never go over 250V the charge controllers will take as much as they can - up to 3.5kw - and push it into the batteries, while also following the battery settings.

Over paneling is no problem.

The reason there are two chargers is so you can optimize your arrays and get the most energy from them that is available at any given time. This will only matter if your arrays are producing under 3.5kw each - in that case the charge controller will adjust its draw to maximize the power coming from the array. If your arrays are pointing different directions, or consist of different panels, or different number of strings, then there will be times when maximizing one means a higher voltage, while the other will have maximum power at a lower voltage. Putting them all on one input, in those cases, would be less efficient, but never dangerous or damaging.

So having the two arrays with different string counts isn't going to hurt anything. Worst case you'll know that at a certain time of day the array with more panels will be producing over 3.5kw, some of it wasted, and the other array less than 3.5kw, with some of the charge controller capacity wasted. Since you're overpaneling on purpose, I doubt this really matters much to you.

The charge controller on the Growatt is a little odd. You have only two current limiting settings: Maximum charge current (regardless of source) and AC charge current (only from the AC/generator input). If you have no AC input, then the first is effectively the solar charge current limiter. If you have AC input then maximum solar charge current will depend on other settings, such as source prioritization, battery status, etc.

In your case it shouldn't matter - you're overpaneling, so just set it to the maximum current your battery bank can handle and call it a day, and if needed set the AC current so it doesn't draw more than the AC input circuit is capable of.

Thanks for taking the time to respond. Confirmed my suspensions. Very helpful.

Sounds like we can proceed as planned

 

[kromc5]

My observations are that after 15 panels, 500w bificials I did not see a noticeable increase for the next 3. I tested slowly bringing 3 strings one at a time. I was curious to observe how much it string would provide. I stopped at 18 panels on the first inverter and charge controller after testing. The plan was to do 18 for each one but I started adding more charge controllers with 12/15 panels each and they are are very close in output. These are all wired on on pv input, I read some where that the 7000k is split via the mppt, if true I wonder if there is any benefit to splitting the panels. I will need to verify this if true I can test by splitting the 18, have 9 on pv1/2. But even now I on inverter 1, 18 panels it has never gone over 38 amps. The charge controllers do better, it will hit 50 amps and the panels are beside inverter 1 and identical. Signature said to say at or under 20 panels on the charge controller 250v model.

I did find out that growatt does not like to low and input voltage 92/98v it consider that unstable and would shutdown down pv input. Only a full restart would get it going again till I rewired 4 of the arrays. I would bet the
250v inverter would have a similiar min voltage.

 

[T-486 Ashepoo]

Couldn't you add additional charge controllers to optimize strings and not exceed any limits? Especially if you want to have strings in multiple directions.

 

[MrM1]

@kromc5 so your growatt is only hitting 50 amps of less on charge current? I'd say try it with using both pv inputs. I thought it was supposed to output 120 charge amps.

As to low voltage input.. My plan is to run 190+vdc into the MPPTs

 

[MrM1]

Couldn't you add additional charge controllers to optimize strings and not exceed any limits? Especially if you want to have strings in multiple directions.

I'd like to if I can find a reasonably priced 250v mppt

 

[Zwy]

tl;dr:
1) The Growatt SPF 12000T DVM-MPV has two 250V max VOC charge controllers. Your target of 200VOC is perfect.
2) Each string can be different, you don't need to match them, just don't go over 250VOC on either one.
3) The charge controller does not use "excess" energy. Once it hits the maximum charge current it simply doesn't convert/consume more. The solar panels will raise their voltage until the current and voltage match the consumption.
4) The maximum charge current is 60A, which means that you'll likely only pull 3.2kw unless your battery operates around 58v
5) The Growatt can limit charge current from the solar array.
6) It has fans. Loud, high CFM fans. You really don't need additional cooling unless its environment is above 40C (104F).


The growatt SPF 12000T DVM-MPV has two separate charge controllers, and you can think of them as completely independent of each other and the rest of the unit. Each one is rated for 250 max VOC input and will not convert more than 3,500W from the array - however they will also not convert more than 60A per charge controller to the battery bank, meaning that you'll typically only get 3kw from each one unless your battery bank goes up to 59v. I'll continue to refer to the maximum 3.5kw, though. You can add millions of panels to each one and as long as they never go over 250V the charge controllers will take as much as they can - up to 3.5kw - and push it into the batteries, while also following the battery settings.

Over paneling is no problem.

The reason there are two chargers is so you can optimize your arrays and get the most energy from them that is available at any given time. This will only matter if your arrays are producing under 3.5kw each - in that case the charge controller will adjust its draw to maximize the power coming from the array. If your arrays are pointing different directions, or consist of different panels, or different number of strings, then there will be times when maximizing one means a higher voltage, while the other will have maximum power at a lower voltage. Putting them all on one input, in those cases, would be less efficient, but never dangerous or damaging.

So having the two arrays with different string counts isn't going to hurt anything. Worst case you'll know that at a certain time of day the array with more panels will be producing over 3.5kw, some of it wasted, and the other array less than 3.5kw, with some of the charge controller capacity wasted. Since you're overpaneling on purpose, I doubt this really matters much to you.

The charge controller on the Growatt is a little odd. You have only two current limiting settings: Maximum charge current (regardless of source) and AC charge current (only from the AC/generator input). If you have no AC input, then the first is effectively the solar charge current limiter. If you have AC input then maximum solar charge current will depend on other settings, such as source prioritization, battery status, etc.

In your case it shouldn't matter - you're overpaneling, so just set it to the maximum current your battery bank can handle and call it a day, and if needed set the AC current so it doesn't draw more than the AC input circuit is capable of.

I have a question and you seem quite familiar with this unit. If PV output is 11Kw, will the unit use 7Kw for charging max thru the MPPT and be able to run the remaining 4Kw thru the inverter if needed?

Or does all PV output have to go thru the MPPT?

 

[Agmills]

I have a question and you seem quite familiar with this unit. If PV output is 11Kw, will the unit use 7Kw for charging max thru the MPPT and be able to run the remaining 4Kw thru the inverter if needed?

Or does all PV output have to go thru the MPPT?

This I would like to know as well

 

[MrM1]

I have a question and you seem quite familiar with this unit. If PV output is 11Kw, will the unit use 7Kw for charging max thru the MPPT and be able to run the remaining 4Kw thru the inverter if needed?

Or does all PV output have to go thru the MPPT?

My understand (and it is very limited so don't quote me) is that some of the all-in-ones like maybe the sok-ark can, but I do not think the Growatt can send the extra power to the loads. I have been told by several seller's tech support that the Growatt 12kw 250 can be over paneled, but the extra power is wasted

BUT... There is a user here on diy, @kromc5, who was told by the same sources (as understand it) that the Growatt can be over paneled, and just smoked the SCC.