Bad alternator? A fully charged battery should read approx. 12.8 without engine running With engine running should read approx. 13.8-14.2 volts
Ideal is 14.2 volts 13.8 is acceptable
With the engine running you should have a reading of 13.5 to 15.5 volts at the battery. So 14 volts is acceptable.
A fully charged battery will read 12.6 volts. A battery reading 12.4 volts is 75% charged. 12.2 volts = 50% charge, 12.0 = 25% charge. You should use a battery charger to charge any battery reading less than 12.4 volts before installing it on the vehicle.
Not necessarily. There are a lot of factors that can keep you from reading 14 volts at the battery, such as corrosion in the cable from the alternator to the battery.
Check alternator with a voltmeter A fully charged battery should read approx. 12.8 volts without engine running With engine running reading should be approx. 13.8 - 14.2 volts
What system? Some circuits go to 0 volts when cranking. If you are reading voltage at the battery, then the battery is dead.
12.5 volts
With the engine not running you should read 12.6 volts on a fully charged battery. With the engine running you should read from 13.5 to 15.5 volts at the battery posts.
Yes, a battery with only a 25% charge will read 12 volts. A fully charged battery will read 12.6 volts.
With engine running 13.8-14.2
It could be the battery or the alternator. Take it to an auto parts store and ask them to do a test of your battery and alternator. Most large auto parts chain stores will do this for free.
Engine running at idle you should read 13.5 to 15.5 volts.