I have a Smart shunt monitoring 4x 105Ah batteries as my house bank on a boat. The shunt is connected to a Cerbo GX for remote viewing on VRM. I have a 100W and a 240W solar panel connected via a 75/15 and 30/100 MPPT charger. I keep a wifi router and some small items like a gas alarm, barometer and a voltage sensing relay that charges a bow thruster battery permanently powered over winter. My quiescent load is around 900mA. The solar usually keeps things topped up daily but over winter when teh sun went on holiday I watched as the SOC dropped to around 82% whilst the battery voltage was reported as low as 12.2V.
I got nervous and asked someone to hop on board and turn the shore power charger on (something I can now do remotely using a Cerbo Relay) and I could sleep again.
My question is, with the Smart Shunt/Cerbo reporting 82% SOC and 12.2v was I premature in engaging the charger would such a low power drain cause such disparity between the reported SOC and that which the Voltage to SOC charts would have you believe should be the case at 12.2v - which is about 50%.
What matters most for the longevity of the battery, the SOC or the lightly loaded voltage?
If I was to set an alarm for discharge state should I go by voltage, or SOC?
Using Relay1 for charger power control I could use the built in generator start function to turn the charger on instead...
