I'm sure this has probably been discussed before but cannot find a definitive answer...
I have a 650W off grid solar PV system with a Victron MPPT 100/20 charger, four 95Ah Exide AGM batteries linked as 2 x 24v pairs and a Victron 800W 240v inverter. I'm powering my computer servers, as they run 24/7, via a UPS that allows me to manually transfer the power connection from grid mains to PV power and back manually without interrruption. The computers are drawing ~250-300 Watts at present.
I'm building an automatic switch to handle the switching between grid mains and PV power, PV power having priority when available, else grid mains being connected. This has to be self contained due to its physical location.
I have an Arduino SBC monitoring the PV and battery voltages and currents, the plan being to use the Arduino to control the inverter remote on-off with a relay, hence causing the (remote) automatic power switch to connect the PV power to my computers when it's on and grid mains when it's off. I also have a Raspberry Pi running the Victron Venus OS.
I've been running the system for a couple of months, manually switching the power between grid mains and PV power based on the weather and data from the Arduino monitor and Venus OS.
I've trawled through endless notes and discussions and come to the conclusion that I should disable the Victron inverter when the battery voltage drops to ~24v on load, which seems to indicate ~50% battery discharge. I should re-enable the inverter when the battery voltage reaches ~26.0v on charge but off load. This appears to give me a sensible cycle between grid and solar power whilst attempting to maximise the life of the AGM batteries.
I'd appreciate any comments on this scheme from those much more knowledgable than me on this. I'm aware I can probably achieve this set up using standard Victron equipment but there's no fun in 'leggo electronics' :-)
Regards
PaulM