What I know about resting voltage on a battery.
12.73V in static unhooked stage at around 80F is good for my T-1275. Same temp, 12.1V is about 50%
So 12.73 to 12.1V, at 70 to 80F, where I camp, is the full length of my runway. With batteries, as with emergency landings, I like the whole runway in front of me. 12.4V, half the runway is behind me. 12.1V, I am out of runway.
Always keep some runway in front of you for emergencies. The closer to 100% state of charge you keep things, the longer your runway for those emergencies.
