Is my inverter undersized?

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SolarLover

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My setup is:

- 17 x Q Cells Peak Duo Black ML-G9 380w Panels (6.46 kWh array)

- 4 x Growatt PowerAmp ML33RTA 3.3 kWh batteries (13.2 kWh) total

- 1 x Growatt SPH3000 6.6 kWh Inverter

I’ve noticed that once the batteries are fully charged that :

1. The inverter starts to whistle

2. The Shine Phone growatt app flatlines the PPV to 3kw

Should I have the SPH6000?

See attached pics & video
 

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Here are some full example of how the inverter is not letting me maximise kWh generated

I estimate I’ll loose out on 1,440 to 2,400 kWh a year due to inverter bandwidth as undersized for array
 

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that would definetly appear to be undersized for the size of your array. Whilst the inverter can cope with your array, the fact it is only 3kw is choking the system. In winter that will make little difference, but for around 2/3rds of the year it's not the best set-up.

It was standard practice to undersize inverters 10 years ago down to 80% of the array size, but inverters are vastly more efficient than they were back then, and I stopped doing that around 8 years ago. If you do get the bigger inverter it will probably need restricting on the export to the grid to 16A, but it will do a much better job of charging the batteries first before having to self limit. If you are using a lot of leccy in the house, it should prioritise energy to battery / house first before limiting anything to the grid, so if you are generating say 5kW and using say 4 kW within the house, it wouldn't limit the 4kW and still allow 1kw back to the grid if the battery is fully charged, or direct 1kw into charging the battery if not fully charged - hope that makes sense.
 
that would definetly appear to be undersized for the size of your array. Whilst the inverter can cope with your array, the fact it is only 3kw is choking the system. In winter that will make little difference, but for around 2/3rds of the year it's not the best set-up.

It was standard practice to undersize inverters 10 years ago down to 80% of the array size, but inverters are vastly more efficient than they were back then, and I stopped doing that around 8 years ago. If you do get the bigger inverter it will probably need restricting on the export to the grid to 16A, but it will do a much better job of charging the batteries first before having to self limit. If you are using a lot of leccy in the house, it should prioritise energy to battery / house first before limiting anything to the grid, so if you are generating say 5kW and using say 4 kW within the house, it wouldn't limit the 4kW and still allow 1kw back to the grid if the battery is fully charged, or direct 1kw into charging the battery if not fully charged - hope that makes sense.
Thanks

Yes makes total sense 👍

Would the current inverter be at risk of damage being overloaded like this? What does it do with excess DC energy if it can’t store in battery or AC export to grid or AC use in house? Where does the DC go?
 
that would definetly appear to be undersized for the size of your array. Whilst the inverter can cope with your array, the fact it is only 3kw is choking the system. In winter that will make little difference, but for around 2/3rds of the year it's not the best set-up.

It was standard practice to undersize inverters 10 years ago down to 80% of the array size, but inverters are vastly more efficient than they were back then, and I stopped doing that around 8 years ago. If you do get the bigger inverter it will probably need restricting on the export to the grid to 16A, but it will do a much better job of charging the batteries first before having to self limit. If you are using a lot of leccy in the house, it should prioritise energy to battery / house first before limiting anything to the grid, so if you are generating say 5kW and using say 4 kW within the house, it wouldn't limit the 4kW and still allow 1kw back to the grid if the battery is fully charged, or direct 1kw into charging the battery if not fully charged - hope that makes sense.
Also my installer is claiming that under Solar Together any system less than 18 panels gets SPH3000 whereas over 18 gets SPH5000

Sound like rubbish to you?
 
Thanks

Yes makes total sense 👍

Would the current inverter be at risk of damage being overloaded like this? What does it do with excess DC energy if it can’t store in battery or AC export to grid or AC use in house? Where does the DC go?
No the inverter will be fine, but working hard. It will initially make itself less efficient, and then shut down if necessary which just stalls the DC side. Inverters have all sorts of inbuilt self protection software to protect themselves. They also partially shut down if they get too hot, one of the reasons I have always preferred to mount them outdoors or in a cool, well ventilated place like a garage.
 
No the inverter will be fine, but working hard. It will initially make itself less efficient, and then shut down if necessary which just stalls the DC side. Inverters have all sorts of inbuilt self protection software to protect themselves. They also partially shut down if they get too hot, one of the reasons I have always preferred to mount them outdoors or in a cool, well ventilated place like a garage.
Ours is a cool garage but the installer just offered us the SPH5000 upgrade 👍
 
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https://solartogether.co.uk/landing
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that would definetly appear to be undersized for the size of your array. Whilst the inverter can cope with your array, the fact it is only 3kw is choking the system. In winter that will make little difference, but for around 2/3rds of the year it's not the best set-up.

It was standard practice to undersize inverters 10 years ago down to 80% of the array size, but inverters are vastly more efficient than they were back then, and I stopped doing that around 8 years ago. If you do get the bigger inverter it will probably need restricting on the export to the grid to 16A, but it will do a much better job of charging the batteries first before having to self limit. If you are using a lot of leccy in the house, it should prioritise energy to battery / house first before limiting anything to the grid, so if you are generating say 5kW and using say 4 kW within the house, it wouldn't limit the 4kW and still allow 1kw back to the grid if the battery is fully charged, or direct 1kw into charging the battery if not fully charged - hope that makes sense.
do you know of a good guide to setup the growatt SPH inverters via Shine Phone or web interface? Some parameters not obvious 😁
 

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do you know of a good guide to setup the growatt SPH inverters via Shine Phone or web interface? Some parameters not obvious 😁
No, I don't fit Growatt, but I'm sure there's a youtube video if you look. Carefull with some of the parameters, most are best left untouched, or if you do fiddle take very careful notes of the standard settings and which part of the menu they are in.
 
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