how to test a car battery with a multimeter

The best way to test a car battery voltage is by using a multimeter.  A multimeter is a handheld device that measures electrical voltage and current in amps.  They will also be able to measure resistance and several other values.

While the chemistry and reasons for battery discharge sound complex, fortunately, testing the battery’s condition isn’t.

| To test a car’s battery with a multimeter, use the following steps

1 – Before being tested the car battery will need to rest for a minimum of 1 hour after it has been driven. Preferably it should be left over night, This allows you to test the “resting voltage” to obtain an accurate measurement.

 

2 – Gain access to the battery and expose the battery terminals. On some makes the battery will have a cover over it that needs to be removed.

 

3 – Multimeters come with a red (positive) and black (negative) lead. Some multimeters used for other testing may have dragon clips or alligator clips.  For testing a car battery, the leads are best if they are of the point end probe type.

 

4 – The multimeter setting to test a car battery is 20 DC Volts. Set the dial on the meter to 20 Volts DC.  This will allow accurate measurement in a range of 0-20 DC Volts, more than enough to capture the batteries capacity within that range.

 

5 – Using the red probe, touch the end of the probe to the positive terminal of the battery. This terminal is normally red and marked with a + sign.

 

6 – Use the black probe to touch the probe end to the negative terminal. This terminal is normally black and marked with a – sign.

 

7 – Have someone turn on the headlights so the system has a bit of a load.

 

8 – If the battery at “resting voltage” reads 12.6V then the battery is fully charged.

 

9 – A reading of 12.3V means the battery is only 75% charged.

 

10 – If the reading is low, the battery should be charged, and the test repeated.

| Car Battery Testing Voltages

The following chart provides you with the normal voltages of a car battery at different stages of operation. Read our full guide on car battery voltage.

Car Battery Voltage Chart showing the voltages of a car battery at different stages of charge and use
Car Battery Voltage Chart

| After the test

If you get low readings on subsequent tests, then this could mean your battery isn’t being sufficiently charged or that the battery has come to the end of its life and needs to be replaced.

It is always worth checking if the battery is being charged sufficiently before replacing it, otherwise the issue could still be there once you have replaced the battery.

| Testing with a Car Battery Monitor

A car battery monitor can be used in the same way as a multimeter to test a car battery, but they are left permanently attached to the battery or the cars electrical system.
Depending on the model they provide the user with the live voltage reading through a set of LED’s, on a digital display or with the more advanced versions via Bluetooth direct to your smartphone.

As the monitor is permanently attached to the battery, you can easily check the state of charge or performance of the battery during normal use.A

| Related Articles

Read more of our guides on car batteries.

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