Question about low voltage
Thread Starter
Intermediate
Joined: Oct 2008
Posts: 38
Likes: 0
From: fort lauderdale florida
Question about low voltage
when the car is running, the voltage is around 13.75.
when the car is off but ignition is in the 'ON' position voltage is around 12.
which one of the above 2 is a clear indicator of actual voltage?
is my battery low?
when the car is off but ignition is in the 'ON' position voltage is around 12.
which one of the above 2 is a clear indicator of actual voltage?
is my battery low?
Pro
Joined: Sep 2007
Posts: 735
Likes: 7
From: Bucks County Pa
Voltage
Hi, neither is really a clear indication of the SOC (state of charge), of your battery. With the car running, the dic, (I presume you are getting the info from the dic,) is reporting the amount of voltage that is coming from the charging system with some loss from wire and connection resistance. 13.75 is fairly normal at idle, and 14.50 is mostly normal at 1500rpm's or above. When the car is off the battery should read at least 12.65 using an external voltmeter to be a fully charged battery, after the flash charge has been dissapated, and the battery disconnected.Connected it should read about 12.45. A battery reading 12.0 volts from an external source will not start the car for long, if at all.
A good way to determine SOC is to charge the disconnected battery for about 8 hours, wait about 4 hours, and then test with a voltmeter. A lead Acid flooded battery should read about 12.65v, AGM 12.70 to be considered fully charged.
A better way is to have it load tested, which determines it's useability. A fully charged battery could still fail under load.
Good Luck
A good way to determine SOC is to charge the disconnected battery for about 8 hours, wait about 4 hours, and then test with a voltmeter. A lead Acid flooded battery should read about 12.65v, AGM 12.70 to be considered fully charged.
A better way is to have it load tested, which determines it's useability. A fully charged battery could still fail under load.
Good Luck
