How to Test a Car Battery with a Multimeter?

How to Test a Car Battery with a Multimeter

When your car won’t start, a weak or dead battery is often the cause. Unfortunately, most vehicle owners do not check their battery until it fails. As a form of preventative maintenance, it’s a good idea to test a car battery regularly with a multimeter – at least twice a year.

Car batteries can be tested at home or in an auto service shop with a multimeter. Or, if you fancy yourself a bit of a DIY mechanic, you can buy a multimeter online for about $10 and test your battery at home. Here’s what to do.

How to Test a Car Battery with a Multimeter?

The following steps address how to test a car battery with a multimeter:

  • Get a multimeter.
  • Set your multimeter to DCV (DC Volts) and ensure it’s adjusted to 20 DC volts.
  • Make sure your battery’s positive and negative terminals are clean.
  • Put the multimeter’s each lead to the correct battery terminal, touching positive (+) to positive and negative (-) to negative.
  • Simply check the voltage of your battery when the car shut off, it should be somewhere around 12.2 to 12.6 (full charge).
  • If the measured reading is less than 12.2 volts, the battery’s resting voltage is weak, which means you need to charge your battery.

Note: If you see a negative number, it simply means you connected the multimeter leads backward. Otherwise, the number is correct.

How to Test a Car Battery with a Multimeter

Perform Cranking Test

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

It’s time to get a reading on the crank cycle. This is the moment when the vehicle is turned on and the battery is most drawn due to the higher amount of energy required to power the starter motor.

To get this reading, a second person is needed to start the ignition. Place the positive multimeter lead on the positive battery terminal and the negative lead on the negative terminal.

As soon as the car is turned on, the voltage reading drops for a short moment, but should not drop below 10 volts. If it drops below 10 volts, the battery does not have sufficient turnover and is prone to failure.

Perform Charging Test

Immediately after the crank cycle, the vehicle begins to idle and receives a constant drain on the battery.

If your battery and alternator are fine, they should read between 14.2 and 14.5 volts. A drop below 14 means either the battery is weak and unreliable for continued vehicle operation, or the alternator is failing. This charge test can also be performed with a DC voltmeter or multimeter.

The alternator‘s job is to generate energy to power the electrical system and charge the battery while the vehicle is running.

To test the alternator, turn on all of the vehicle’s electrical devices – headlights, interior lights, air conditioning, and stereo. This maximizes the voltage load. If the multimeter reading falls below 13.5 volts, the alternator is having trouble charging the battery properly and may need to be replaced.

Watch Video To Learn More About How to Test a Car Battery with a Multimeter:

Share:

Leave a Comment

On Key

Related Posts

What Others Are Asking

How Many Amps Is A Car Battery?

An average car battery has a capacity of around 48 ampere-hours; When fully charged it will deliver 1 amp for 48 hours, two amps for

Is red positive on a battery?

Yes, the red one is positive (+), and the black one is negative (-). Never connect the red cable to the negative battery terminal or a vehicle with a dead battery.

Which Is Positive Red or Black?

The red one is positive (+), and the black one is negative (-). Never connect the red cable to the negative battery terminal or a vehicle with a dead battery.

How Does a Car Battery Work?

Just like your TV remote or fancy electric toothbrush, your car needs a battery to run. If it dies, your car won’t start, leaving you