How to Test a Car Battery

Car batteries eventually stop working and it's important to diagnose the problem correctly. Learn how to simply and safely test your car battery.

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Introduction

Car batteries are essential for vehicle operation, but like everything else, eventually they fail. You'll know this has happened when your vehicle won't start or the motor turns over weakly. When your battery runs down and can't start your vehicle, it's important to determine if it's drained and needs to be recharged, or it's too weak to hold a charge. Sometimes low or dead batteries simply need charging or boosting. When they lose their ability to hold a charge, they need replacement.

Proper battery testing makes it easier to figure out what's wrong with your battery. Learn how to do a detailed test of your car battery with a dedicated battery tester. You could use a multimeter, but you won't get as much information about what's going on inside the battery.

Tools Required

  • Car battery tester
  • Multimeter or voltmeter (optional)

Project step-by-step (6)

Step 1

Avoid Driving for Several Days, Then Locate the Battery

  • Wait at least a few days without driving to test your car battery, unless you’ve already determined it won’t start and suspect battery issues.
    • Your car’s alternator charges the battery while the vehicle is running. Testing the battery after not driving for a few days will tell you how well your battery is holding a charge. If it runs down significantly, it probably needs replacement.
  • Lift your vehicle’s hood when you’re ready to test the battery, if that’s where it’s housed. If not, find it elsewhere in the vehicle.

Locate the BatteryRobert Maxwell for Family Handyman

Step 2

Connect the Battery Tester

  • Remove the red plastic protective cover from your battery’s positive terminal.
  • Connect your battery tester’s red cable clip to the battery’s positive terminal.
  • Connect the black cable clip to the negative terminal, then turn on the tester.
    • Be sure to position the tester in a spot where it sits flat and won’t fall down into the engine later when you perform cranking tests with the vehicle running. Car batteries don’t have enough voltage to electrocute you, so no need to worry about that.

Connect the Battery TesterRobert Maxwell for Family Handyman