Can Growatt SPF 5000ES handle AC coupling?

[Offgrid Aussi]

Hello Guys,

My off-grid setup consists of only one 3kW solar array, a Growatt hybrid inverter (SPF 5000ES) and a 13kW battery.
To use the full potential of the SPF5000, I want to add a second solar array, but that inverter can only handle one.

A Growatt 5500MTL-S that can handle two arrays rests in the shed and could be utilised, but that is a grid-tie inverter and will only work with a stable 220V connection. So I would have to connect it to the AC output port of the SPF5000.



I heard that the Victron MultiPlus can handle AC input on its output port, so you can add grid-tie inverters to your off-grid system and push AC currents "backwards" through the Multiplus to charge the batteries, but can you do that with the Growatt SPF 5000ES as well? I tried to get a response from them, but had no luck so far.

Has anyone here been there and done that?
I rather consult with you guys than take my chances and watch everything go up in smoke.
So any thoughts are greatly appreciated.

Kind Regards
Offgrid Aussie

 

[sunshine_eggo]

No. AC coupling requires the off-grid inverter be able to shift the output frequency and force the GT inverter to disconnect.

GT inverters don't regulate their output. They expect an infinite grid in which to dump their output. An inverter capable of AC coupling can use the surplus AC provided by the GT inverter and charge the batteries; however, once the batteries are full, there is nowhere for the power to go, so the inverter shifts the frequency up or down 2-3Hz or so, and forces the GT inverter to disconnect.

Victron inverter/chargers and most Tier-1 inverter (Magnum, Schneider, Outback, midnite, SMA, etc.) have this function. Some "hybrid" inverters that are capable of optionally backfeeding to grid can do this.

 

[Offgrid Aussi]

once the batteries are full, ... the inverter shifts the frequency up or down 2-3Hz or so, and forces the GT inverter to disconnect.

Thank you very much, I didn't know that. What a great way to tell the GT to shut down. I always wondered how they do that.

So this setup would work with a MultiPlus, or if the SPF 5000ES could do frequency shifts, which you say it can't right?.
I was kind of hoping that the Growatts could communicate on their CAN bus to make sure they don't fry themselves.

Anyway, I might find a way to extend the existing array with similar sized solar panels to get a little more than the installed 3kW.
Thanks again for your insight and have a sunny day!

 

[sunshine_eggo]

Thank you very much, I didn't know that. What a great way to tell the GT to shut down. I always wondered how they do that.

Something I just learned is that UL1741SA rated GT inverters - they can use the frequency shift as a throttle, e.g., if 50Hz is max and 53Hz is disconnect, it will throttle itself in that range, e.g., at 51.5Hz, it will throttle the GT inverter to 50%.

So this setup would work with a MultiPlus,

Yes

or if the SPF 5000ES could do frequency shifts, which you say it can't right?.

Correct.

I was kind of hoping that the Growatts could communicate on their CAN bus to make sure they don't fry themselves.

Anyway, I might find a way to extend the existing array with similar sized solar panels to get a little more than the installed 3kW.
Thanks again for your insight and have a sunny day!

You can always add another MPPT. Growatt has some that are inexpensive and supposedly communicate with their inverters.

 

[Offgrid Aussi]

I'll look into that. Thanks again.

 

[flintofgullies]

No. AC coupling requires the off-grid inverter be able to shift the output frequency and force the GT inverter to disconnect.

GT inverters don't regulate their output. They expect an infinite grid in which to dump their output. An inverter capable of AC coupling can use the surplus AC provided by the GT inverter and charge the batteries; however, once the batteries are full, there is nowhere for the power to go, so the inverter shifts the frequency up or down 2-3Hz or so, and forces the GT inverter to disconnect.

Victron inverter/chargers and most Tier-1 inverter (Magnum, Schneider, Outback, midnite, SMA, etc.) have this function. Some "hybrid" inverters that are capable of optionally backfeeding to grid can do this.

Hi, will a "hybrid" inverter set to zero export work on the AC output of three Growatt SPF 5000ES set as three phase?

Thanks in advance.