12V Lead Acid Battery DOD Readings

[ForgivenCreation]

I tried looking all over and can't seem to find a definite answer.
Should I be measuring my Depth of Discharge Voltage while stuff in plugged in and running or with the inverter / electronics off and the battery sitting after a bit.
Battery sitting with no load is 12.25V range but with LED lights on drops down to 12.05V range. I am aware that below 50% hurts Flooded Lead Acid Batteries but is this number best measured disconnected completely or with stuff drawing some power or full load?

 

[sunshine_eggo]

Completely disconnected for 24 hours.

"Hurt" is not an accurate characterization. You will get reduced cycle life.

 

[OzSolar]

Voltage is generally a poor method to determine SOC (state of charge)

Are these flooded batteries? If so then a hydrometer is a great way to check SOC.

Counting AH in/out with something like a Victron Smart Shunt is another great way to do it. Not only does is count energy in/out it will help you learn all sorts of things about your system.