sparrowhawk
Christian Prepper
There appears to be some voltage settings to control the dry contact switch, so if I can figure out how to utilize it I will use it to turn the water heater on via a relay. Probably once the charger hits float mode. And then off if voltage drops below whatever voltage I set. All of which I still need to determine. I would also like to avoid rapid on/off relay switching if possible."Dry contact" may be the simple way to do it.
I think Outback and/or Midnight has that, programmable for something like voltage or SoC.
Considering the curves of lithium, if Growatt can switch a relay on and off part way up the voltage curve, it could cycle up and down a few percent near fully charged, diverting power to the heater without curtailing PV production.
Analog control could be most ideal. If the waveform didn't cause issues, a dimmer (uses SCR to cut in part way through sine wave) with servo circuit could hover at some battery voltage without charge/discharge cycling.
(AC not DC circuits feeding water heater, of course. Unless you buy the heating elements with DC thermostat built in. Would still need DC relays for timing or dump load functions in that case.)
If I can't figure out how to do that then my fall back is the timer.