How to Test a Car Battery

Worried that your battery might need to be replaced? Before you run out and buy a new one, there are a couple of quick checks you can perform at home with just a multimeter that will give you a good indication of your car battery's health. Here's what to do.

Innova auto-ranging multimeter

Innova Auto-ranging Digital Multimeter | Innova

Test the battery voltage

  1. Turn off the ignition and any accessories like lights or the radio in the vehicle.
  2. If your multimeter is not autoranging, set it to 20V DC.
  3. Place the red lead on the positive battery terminal (indicated by a red cover or a + symbol).
  4. Place the black lead on the negative terminal.
  5. Read the measurement. If the reading is below 12.4 volts, you may need to charge your battery.
Pro Tip

If you see a negative number, it simply means you've attached the multimeter leads backwards. The number is still otherwise accurate.

    DieHard batteries with an Advance Auto Parts gift card

    Perform a cranking test

    Monitoring the voltage during cranking can provide better insight into whether a battery simply needs to be charged or if it needs to be replaced.

    1. Turn off the vehicle and all accessories.
    2. Disable either the fuel or ignition system — whichever is easiest on your vehicle. This is necessary because the test is dependent on the vehicle cranking, but not starting.
    3. Place the positive multimeter lead on the positive battery terminal and the negative lead on the negative terminal.
    4. Have a helper turn the ignition on for no longer than 15 seconds and watch the multimeter. If the battery voltage drops below 9.6 volts, this is an indicator of a weak battery.

    If you suspect your battery is failing, stop by your local Advance Auto Parts. Advance offers quick curbside testing without you needing to leave your vehicle. If you need a new battery, a knowledgeable Team Member will help you select the right one for your vehicle and install it for you while you wait*. Advance will even recycle your old battery for you. Learn more about free services here.

    *Car battery testing and installation available on most automotive vehicles, at most locations, unless prohibited by law.

    Last updated March 18, 2021

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