mm wrote:
A fully charged battery is about 12.6 volts. Of course yours is not
fully charged, but you could charge it. Voltage stays near 12 volts
even while a battery is 80% discharged. I forget the math, but it
makes sense.

Yeah, voltage is not a good way to measure state of charge. Use a
Hydrometer.

State of charge/voltage (at 80F):


100% = 12.65
75% = 12.45
50% = 12.24
25% = 12.06
0% = 11.89