The voltage/charge curve of a lead acid battery is: %chg Voltage S/G 100 12.7 1.265 75 12.4 1.
225 50 12.2 1.190 25 12.0 1.155 0 11.9 1.120 A bit of web searching will prove that. I stand beside my statement that seeing 11.89v across the battery as being implausible on a car that you've started and is running.