What should the battery voltage be when car is running?

14.6 would be high normal, 13.5v would be acceptable battery charging voltage. Check voltage across the battery terminals, leave the black ground wire at the battery post (-) move the red volt lead to the large wire post at the alternator if the voltage is different you have a voltage drop (youtube voltage drop there is a good video there). At rest engine off battery voltage should be 12.6 volts at rest if battery is charged and good.

CHARGING VOLTAGE SHOULD BE ABOVE 13.2

above 12.75

Anything below 13.5 volts with loads like lights, A/C and wipers on. No less than 13.5 volts.