#1. About Multimeter
A multimeter is a device used to measure the circuit's electric current, voltage, and resistance—professionals who know how to use a multimeter.
They attach the two leads to different parts of an electric system to check the rate or level of the voltage. We use this to review the voltage of the battery of the car.
#2. Measure with Multimeter
When you measure with your multimeter, it will calculate the DC voltage shown by a solid line and dashed line above V, set it to 20 means it will measure the volts between the range of 0-20.
Set the red probe to( + ) terminal and the black probe to (-). Suppose you get minus (-) in reading in front of it. It is the wrong way.
Check whether the reading is lower than 12.6 or not.
The current supply of a regular car should be 12.6 volts. Always test/check your car battery if your vehicle does not start for at least 2 to 3 days to know the voltage rate in the rest position. It is called the resting voltage.
If you drive a car and then check the voltage, it will give you a higher reading than that of when the vehicle is in rest position(resting voltage). To check the accurate voltage, leave the car overnight and test it the following day.
The rate of resting voltage should not be lower than 12.6 V. A battery with a reading of only 12.2V is 50% charged and discharges below 12V.