I have a novice (perhaps stupid) question regarding use of overflow (not sure whether that is the correct therm) to heat water.
I have a Cerbo GX + 3x Multiplus II 48V/3000 + pylontech batteries. The system is ESS.
I also have a water tank and electric heater (2 kW) in it.
How should I manage the electricity when the battery is full and the overflow is going back to grid, so in that case the electric heater will turn on and store the energy to the water instead of going to grid?
I guess that I can use the relay 1 (or 2) on the Cerbo GX to turn the heater on/off or something like that. Is that correct? Or am I wrong?