Extend single Growatt solar system question

[MikeMynis]

Hi guys, I have 1 Growatt SPF5000ES with 9 450 Watt solar panels and a lead acid battery bank. It works okay, but we need more power.

So I bought 8 extra panels each 550 Watt plus an extra Growatt SPF 5000 ES.

According to the Growatt documentation, I can parallel both Growatts, extending it to a 10kW output system.

For this to do I need to parallel the grid AC input to both Growatts. I also need to parallel the outputs to the loads, and set both Growatts in parallel mode via the menu, after connecting the communication cables between them.

Then I also need to parallel the battery to both Growatts.

This is the preferred setup according to the docs.

But I don't want to parallel the battery bank to both Growatts.

I want a separate new battery bank (LiFePO4) to Growatt #2.
(and keep the Lead Acid battery bank connected to Growatt #1)


So each Growatt has their own solar array and battery bank connected.
The grid inputs are paralleled and so are the load outputs.

Is this okay to do? Anyone having experience setting this up?

Thanks,
Mike

 

[timselectric]

To be paralleled, they must be connected to the same battery bank. And the battery cables need to be the same round trip length.

 

[timselectric]

This is the preferred setup according to the docs.

It's a requirement, not a preference.

 

[MikeMynis]

Hmmm, okay. That means replacing the lead acid bank with the Lithiums... And then paralleling them.
Thank you for clearing that up

 

[peak.watt]

To extend on what timselectric has said; the cable length being equal rule is so that the batteries "see" the same voltage from each inverter, or put an other way each inverter sees the same voltage from the battery.

So for example if you have 2 inverters going to a single breaker, then on to a bank of batteries, you can have a negative lead that is twice as long as the positive between the breaker and the battery bank - in fact this is a common occurrence because you want one lead going to one end of your bank of batteries (or top if its a rack) and the other lead going to the other end, so usually one will end up being longer.

You *cant* (or shouldn't) have the leads on the inverter side of the breaker having different lengths - say inverter1 has positive and negative leads of length X, and inverter2 has positive and negative leads of 2 times X. This will result in inverter2 "seeing" a lower voltage when drawing from the battery, and depending on the inverter, warnings or faults will be thrown, or funky things might happen.