A fully charged good condition battery should read 12.6-7 after setting at least 24 hrs. If it reads higher than that, you are still seeing a surface charge. If it is lower than that, like 12.2-4 it is not fully charged, or the battery is older and not in such good condition anymore, and is on borrowed time,....... but may still be usable for quite a long time.

For myself, if any battery of mine is going to set for more than a month, it is connected to a maintainer float charger continuosly which will hold the voltage at 13.2-4 volts, and no worry of the battery freezing then either. But w/o charging, the voltage should be held at 12.5-6 on a good battery, and whatever max voltage you can attain on a weak battery.

A 1-2 amp float charger can maintain several batteries at the same time if they were fully charged to begin with.

If interested....................
Remember, any battery that is less than full charged, is sulfating inside. And lead acid batteries will loose at minimum 10% of their charge per month.

C&P'd from the experts
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Voltage State of Charge
12.6+ 100%
12.5  90%
12.42 80%
12.32 70%
12.20 60%
12.06 50%
11.9  40%
11.75 30%
11.58 20%
11.31 10%
10.5  0%