How to Check Your Battery

Have you ever hopped in the car and turned the ignition just to find that it won’t start? Whether you were just planning to go on a joy ride or you had a seriously important obligation, chances are your dead battery messed up your plans. Luckily, there are a few ways to check your battery at home so that you can prevent this from happening again.

What Tools Do I Need?

When testing to see if your car’s battery is fully charged, an accurate measurement of the battery’s voltage must be taken. To get this measurement, you’ll need a voltmeter, which is an instrument used for finding the electrical potential difference between two points in an electrical circuit. Here is what a voltmeter looks like:

How Do I Test with a Voltmeter?

To start the test, ensure your vehicle is shut off completely. Your car’s ignition should not have the key in it and all of the vehicle’s lights should be off (both inside and out).

1. Locate the positive (red) voltmeter test lead and connect it to your car battery’s positive terminal.
2. Locate the negative (black) voltmeter test lead and connect it to your battery’s negative terminal.
3. Determine the battery’s charge by comparing the voltage reading on the voltmeter to this key:

• • Voltage: 11.8+ = 0% Charge
  • Voltage: 12.0+ = 25% Charge
  • Voltage: 12.2+ = 50% Charge
  • Voltage: 12.4+ = 75% Charge
  • Voltage: 12.6+ = 100% Charge

Clearly, a 0% battery charge is not a good sign. You want your car battery’s voltage to be in the 12.4+ to 12.6+ range, meaning it has a 75-100% charge. If you’re below this range, it’s time to take your vehicle into your local repair shop.

*REMEMBER* When removing the voltmeter leads, always disconnect from the negative battery terminal first!

No Tools? No Problem.

If you don’t have a meter to measure the voltage of your battery, a quick test of your car’s electrical system can be helpful in alerting you to potential issues with your battery. Perform a headlight test by starting your car and turning on the headlights. Observe the amount of light shining from the bulb to figure out if something isn’t quite right:

• If your headlights are dim, this tells you they are running off of the car’s battery and that very little or no charge is being produced by the alternator.
• If you rev your engine and the lights get brighter, the alternator is producing some current but is not sufficient enough to keep the battery charged when idle.
• If your headlights produce normal brightness and do not dim or brighten when revving the engine, your battery is likely operating properly.

When Should I Check My Battery?

If you really want to prevent a dead battery, it’s best to check it on a regular basis. Waiting to check the voltage until you start noticing signs of weakness is a recipe for disaster. Even checking your vehicle’s battery twice a year can be significant in reducing its chances of failure.

Your Resource for Auto Maintenance in Frederick, MD

Want to know of another easy way to ensure your car battery doesn’t die on you when you least expect it? Bring your vehicle into Ken’s Automotive & Transmissions for regular auto maintenance in Frederick, MD! Our check-ups help catch and diagnose issues with your car before they cause you an inconvenience or costly repair, and regular maintenance can keep your vehicle in safe condition all year round. Call us to schedule your appointment today.