Growatt SPF 3000TL HVM-24 Off-Grid Inverter with seperate MPPT to charge the battery.

[Dieter]

Hello everyone,
My first Post here

After a bit more then a year of measuring the performance of a 360Wp solar pannel with microconverter and measering our usage of grit power, i am finaly trying to design a solar system.

3f+N 400V 32A grit connection
8x 370Wp solar panels (just under 3kWp)
8x LIFEPO4 280Ah cells for a 24V - 6.7kWh battery
1x Growatt SPF 3000TL HVM-24 Off-Grid Inverter

The growatt suits our needs of max power, works with the 24V battery, but only accepts 1.5kW of solar power.
The next models all work with a 48V battery, this would increase the cost a lot with only a small extra savings in the power bill.
I don't think this model can be installed in a double configuration to split the solar power.
(-> or is it possible to connect them with a different phase without connecting them with each other, like microconverters do ?)
So i was thinking to use a MPPT to load the battery and use the inverter only to unload it to 230V.

Good idea, bad idea ?
Any other options ?

Thank You for the help.
Best regards, Dieter.

 

[Ampster]

So i was thinking to use a MPPT to load the battery and use the inverter only to unload it to 230V.

As long as you do not exceed 140 Amps you could connect 4 panels to the Growatt and 4 to an MPPT charge controller. What are the solar voltage and Amp limits of the Growatt?

 

[Dieter]

Max 102VDC and 50A.
Also just noticed that the battery type for this inverter is lead-acid.
The 48V models also support Lithium.

 

[Ampster]

Also just noticed that the battery type for this inverter is lead-acid.

If you can adjust the voltage settings you can make the Growattt work for LFP. Otherwise just an MPPT charge controller would be better for charging if you get one that you can adjust voltage settings. Then all you have to worry about on the Growatt is the low voltage disconnect setting.

 

[Dieter]

The battery parameters are settable 'user defined'
Bulk charging 24~29.2V
Floating charge 24~29.2V
Low DC cutoff 20~24V

Any suggestions of MPPT brand ?

 

[Ampster]

I charge my LF280s to 3.45 per cell which would be Bulk of 27.6 Volts. I would disable Float or set it to 3.3 volts per cell if you have regular loads attached. My Low DC cuttoff is 3.0 volts or 24 volts.
I have never purchased a charge controller. I have an All In One inverter by Outback. I know they make high quality charge controllers. There are others in that class.

 

[Dieter]

Would it realy be an issue to use 2 inverters in a 3f network, each on another fase offcourse.
I can't think of anything why they should be 'talking' to each other.
In a grit-tied system off course.

 

[Ampster]

Would it realy be an issue to use 2 inverters

It would be a cost issue if you do not need the extra capacity of the extra inverter. I do not know the details of connecting them in parallel. Adding a charge controller would be what I would try first since it would be a lot less complicated.
However I do not think it would be an issue to exceed the solar Watt limit of the Growatt (also called over paneling} as long as you do not exceed the Amperage and Voltage limits. There are a number of threads discussing over paneling Growatt invertrers and you should read them or confirm with your supplier to be sure. My All In One can exceed the Wattage of the inverter as long as I do not exceed the Amperage and Voltage limits of the solar input.

 

[Dieter]

The growatt inverter is actualy realy cheap comparing with a victron mppt ?.

With the 102V and 50A max on the inverter.
And 40,9Voc and 11.52Isc from the pannel, should allow a 2s4p configuration.
Right?

 

[DThames]

I have a pair of Growatt 3000w, 24v set up in split phase with 1500w PV going to one, 1800w PV going to the second one, and an EPEver-AN 40amp with 1200w PV all charging the same battery bank. Yes, you can do that.