2 x Growatt SPF5000ES Parallel mode: weird situation

Hi guys,

I have 2 Growatts SPF5000ES in single phase, parallel mode.

• Everything is connected in parallel, as the documentation explains.
• One single battery bank is connected to both Growatts, same cable length, etc.
• Growatt 1 has solar panels directed South
• Growatt 2 has solar panels directed East

So in the morning Growatt 2 is the first one that starts generating power.
A few hours later Growatt 1 starts generating power.
Around noon they are both generating approximately the same amount of energy.
Later in the afternoon, Growatt 1 generates more than Growatt 2.

But the strange thing is that in the morning, Growatt 2 reports that it's CHARGING the battery bank (which is good), while Growatt 1 reports DISCHARGING the battery bank.

Please see the screen video I made:

Can anyone explain to me what's going on here?

MikeMynis said:

But the strange thing is that in the morning, Growatt 2 reports that it's CHARGING the battery bank (which is good), while Growatt 1 reports DISCHARGING the battery bank.

Click to expand...

Not at all. Makes total sense.

MikeMynis said:

So in the morning Growatt 2 is the first one that starts generating power.

Click to expand...

^ This is why

You have loads. They are sharing them; however, #1 is consuming more than it's generating, so it's drawing from the battery. A net draw from the battery is a discharge.

it's reporting:

288W loads
150W PV charging
-166W battery discharge
Difference is inefficiencies.

288W / (150W + 166W) = 91% net efficiency.

Loads are bigger than charging, so the inverter is discharging the battery to power loads.

sunshine_eggo said:

Loads are bigger than charging, so the inverter is discharging the battery to power loads.

Click to expand...

Hi, thank you very much for explaining this.

For Growatt #1 I can understand this. It's getting only ~150W from solar. But Growatt 2 is getting ~1584W from solar.

The total load is just ~505W.

In total there is more solar power than the load. In my logic, Growatt #2 is charging 1262W to the battery, while Growatt #1 is "discharging" (= taking power from) 177W from the battery. In total this would be 1262-177 = 1085W into the battery.

So effectively the battery IS charged and the loads are powered.

Still, I don't get this strange Growatt logic.

Why would - in a parallel configuration, where both inverters communicate with each other, the one inverter that lacks solar energy, start taking from the battery, when the other inverter has enough solar power for charging the battery and the load...

MikeMynis said:

Why would - in a parallel configuration, where both inverters communicate with each other, the one inverter that lacks solar energy, start taking from the battery, when the other inverter has enough solar power for charging the battery and the load...

Click to expand...

They don't "communicate" everything with each other. The master just sets timing for the AC signal. Each inverter reports its own individual parameters.

You are being inconsistent in your interpretation of data.

You are willing to accept that each inverter is reporting:

1) it's individual PV production
2) it's individual load

But you expect the inverters to report an aggregate battery load?

Growatt #2 is producing more than it's using, so it's charging.
Growatt #1 is producing less than it's using, so it's discharging.

If you're willing to accept that #1 and #2 are individual values, you must accept that the charge/discharge indicator is also an individual value.

Remember these are "budget" inverters.

B-Mod said:

Remember these are "budget" inverters.

Click to expand...

Tier one units in parallel react the same way, to unbalanced solar input. There's no way around it.

MikeMynis said:

I don't get this strange Growatt logic.

Click to expand...

I would be more worried about you if you did get it, growatts don't necessarily make a lot of software sense ?

Hello,
I also want to connect two inverters in parallel.
I have a question: inverters must have the same firmware?

yare said:

I have a question: inverters must have the same firmware?

Click to expand...

Yes

timselectric said:

Yes

Click to expand...

And that's probably gonna be a problem. I have a Growatt 5000 since 2023. Now if I buy another one, it will definitely have different firmware and also different hardware.

yare said:

And that's probably gonna be a problem. I have a Growatt 5000 since 2023. Now if I buy another one, it will definitely have different firmware and also different hardware.

Click to expand...

It's a high possibility.