To determine if your battery is fully charged, you will need to measure your battery's state of charge with a voltmeter. You can use an analog or digital voltmeter, but a digital meter will give you an easier-to-see, more accurate reading. If you are a do-it-yourselfer, remember to always wear a pair of rubber gloves and goggles whenever you service your battery. This will protect your hands and eyes from acid.
Follow these steps to test your battery:
- Before you begin testing, make sure the ignition key and all of your vehicle's lights are off.
- Connect the red or positive voltmeter test lead to your battery's positive terminal.
- Then, connect the black or negative voltmeter test lead to your battery's negative terminal.
- Compare your reading to this chart:
- Always remove the negative terminal first. If the battery terminals do not come off easily, use a battery terminal puller to remove them. Do not use a screwdriver to pry the terminals off because it can break the internal connections of the battery post.
- Take your battery terminal cleaning tool, which should have different extensions for different sized terminals, and use it to clean off the terminals and posts. Also, use a quality battery cleaning solution, which is available at your local Pep Boys.
Good
- Accepts and holds charge
- Easily recharges and returns to service
- Above 12.4 volts reading
- Under 4 years old
Bad
- Will not accept or hold a charge
- Under 12.0 volts reading
- Cannot produce adequate cranking amps
- Over 5 years old
