How to Check a Car Battery

Co-authored by Jason Shackelford

Last Updated: July 15, 2024 Fact Checked

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You go to start your car only to discover that the engine won't start and the headlights won't turn on. That's a sign that it's time to check the battery. Not sure how? Don't worry—this article will walk you through how to check your car battery step by step with either a voltmeter or a power probe. If you don't have either of those things, we'll also show you how to check the battery by cranking the engine.

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Method 1

Method 1 of 3:

Check Your Battery with a Voltmeter

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^{[1]
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Check and clean the battery terminals.

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The positive lead on a voltmeter is usually red.^{[2]
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Check the voltmeter. If your battery is in good condition, the voltage should be between 12.4 and 12.7 volts. A reading lower than 12.4 volts means that your battery needs to be charged.^{[3]
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- If the reading is lower than 12.2 volts, "trickle charge" the battery, which is a slow charge. And then re-check.
- If the reading is over 12.9 volts, you have excessive voltage. Turn on the high beams to remove excessive voltage surface charge. Over voltage may be an indication the alternator is over charging the battery.
- While you have the voltmeter handy, you may also want to do load testing.

Method 2

Method 2 of 3:

Check Your Battery with a Power Probe

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The positive lead on a voltmeter is usually red.
Connect the tip of the probe to the positive battery terminal. Check the probe for voltage reading.
If your battery is in good condition, the voltage should be between 12.4 and 12.7 volts.^{[4]
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Method 3

Method 3 of 3:

Check Your Battery by Cranking the Engine

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"Crank" the engine by turning the ignition until the starter engages and hold for 2 seconds Have an assistant crank the engine while you check battery voltage drop.
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At the time of the crank, check the reading of the Power Probe. It should not go below 9.6 volts.^{[5]
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- A battery with a volt reading less than 9.6 volts means the battery is sulfated and not holding/accepting the charge.
- Alternatively, you can get the battery tested at an auto parts store or a repair shop.^{[6]
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  Jason Shackelford
  Auto Technician
  
  Expert Interview. 11 June 2019.}
- They usually test your battery at no charge.^{[7]
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  Expert Source
  
  Jason Shackelford
  Auto Technician
  
  Expert Interview. 11 June 2019.}
- Home diagnosis is rather difficult and not very accurate.^{[8]
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  Expert Source
  
  Jason Shackelford
  Auto Technician
  
  Expert Interview. 11 June 2019.}

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Tips

Most car batteries last between 4 and 5 years. In hot climates, they may only last about 3 years. If you charge your battery and find that it won't hold a charge while your car isn't running, replace the battery.^{[9]
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You can test and charge your battery at your local auto parts store.

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Before buying a new alternator, have the system checked more thoroughly.

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Warnings

Never short between battery terminals. Serious burns, damage to the terminals or an explosion from hydrogen gas can occur.

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