How does it work

[fatjay]

I'm a jump first, look later type of guy, but I'm not sure about this.

I have a 3kw growatt, a 15kwh battery, and 4.2kw array. I set my inverter to stop discharging the battery at 20% capacity remaining. The sun sets, the battery is at 100%, the panels go dark, and I'm using 1500w of power. I start at 15kwh capacity, going down each hour 1500w until 8 hours later when my battery hits 20%.

At this point, my inverter switches from batteries to grid. Which of the following happens now?
1. My inverter charges teh batteries while continueing to power the 1500w load. The batteries reach 100%, then the grid shuts off and powers the 1500w load until they reach 20%, or the panels start producing, whichever comes first.
2. My inverter charges the battery while continueing to power hte 1500w load. The batteries reach 100%, but the system remains remains on grid until solar is detected then switches to battery/solar.
3. My inverter leaves the battery at 20% but powers from the grid the 1500w load. Once solar comes up, the inverter prioritizes the load, then when there is spare, it charges the battery.
4. It all catches fire and explodes.

Obviously i haven't hooked everything up yet, I'm still in the process. But I'm working on building everything out.

 

[sunshine_eggo]

5. Your inverter passes through the grid power to your loads and uses grid power to charge the battery. Your grid power must be sufficient to supply loads AND charge. Charging stops and starts according to the model and settings you select.

Inverter/chargers can only do one or the other - never both at the same time. The same circuitry for inverting DC to AC is used in reverse to convert AC to DC.

 

[Mattb4]

Hopefully you received a manual with your inverter that lists the operating choices. If not it would be a good idea to find it online or ask for it from the place you bought the Growatt. Often difficult to read and understand at first the more you go back through it and get experience from trying the various choices the clearer it will become. These choices will select the preferred power source and when transfer will happen.

For one thing your battery capacity as a form of preferred power source transfer may only be available with battery communication whereas voltage amounts would be the method for use with a Standard (dumb) battery. Which also should come into play for battery types other than lithium.

And keep in mind #5 that S_E listed above.

 

[fatjay]

Yes, I have a manual, both in print and pdf. I've read it a few times, but it's a bit vague. I know about SUB and SBU modes, it just doesn't really go into detail about what happens after the battery is charged in SBU, which is the route i'm going.

 

[Mattb4]

Not sure what you unit does since some will shutoff all charging once full and only recommence when a recovery setting point is reached. Others will float and continue to use PV to supply loads.

 

[sunshine_eggo]

Review settings 12 and 13.