To avoid a dead battery or identify a faulty one, you must check your car battery's voltage regularly. It is important to know what the proper voltage should be. A voltage that is too low or too high may indicate significant battery problems and cause dangerous driving conditions.
To check your car battery's voltage you need a voltmeter. Digital voltmeters are available in automotive stores, electronic stores and online. It is important to purchase a digital and not an analogue voltmeter, as analogue voltmeters use a needle readout, which is hard to read and less accurate.
Before you check your car battery, make sure your car is not running. Eye safety also is important to safeguard against any battery acid or possible debris. Lastly, remember to remove all jewelery, because it is a good conductor of electricity.
Checking the Battery
To check your battery, connect the positive voltmeter wire (red) to the positive side of the battery, then connect the negative voltmeter wire (black) to the negative side of the battery. The battery voltage of a car that has been at rest should read between 12.5 and 12.8 volts.
If your battery reads below the recommended voltage it must be recharged. After jump-starting the battery, the voltage while the car is idling should read between 13.5 and 14.5 volts. If your battery's voltage still is low, it may be time to replace your battery or you may have an alternator problem. At this point it is best to seek professional help.