A multimeter can measure voltage, but that’s only one of its functions. It can also measure resistance and current. So, you need to select the function on the dial as the right scale. You also need to observe some measures like making sure to use eye protection. You also need to avoid measuring battery voltage immediately after it has been charged fully.
The dial selections can be divided into three: resistance, current, and voltage. The symbol for resistance is omega (Ω). The letter A denotes current for amperes. Voltage is denoted by the capital letter V. The voltage group has various settings as well. It indicates the progression in sensitivity from 200 millivolts to 500 volts. Dial selections may also include DC and AC settings. The symbol for DC is a straight line or no line. The mark for AC voltage is a wavy line. To measure a 12V system, you need to select the DC voltage, but set it at the 20V range.
Before measuring the voltage, make sure to disconnect the battery from the circuit by removing the cables. This will eliminate the chances of stray current draw affecting the reading. Make sure to plug the red lead into the VΩ port and then plug the black lead into the COM port. Touch the negative terminal with the black lead and the positive terminal with the red lead. Check out the reading on the meter. It will tell you what the voltage is between the two terminals. If the battery is good, the reading will be higher than 12 volts. It will hit the 12.8 volts if it is fully charged and 12.1 volts if it is about 50 percent charged. If is it about 11.9 volts or lower, this means it isn’t charged.
You can test your 12V battery using two other voltage tests. You will need alligator clips on your voltmeter leads. To test the voltage, make sure to connect the battery cables. Start the ignition while holding the leads on the positive and negative terminals. You will notice that the voltage will drop, but it should not drop below 9.5 volts. It needs to be replaced if it drops below this voltage.
If you would like to test the charging system, make sure to hold the voltmeter leads on the terminals. Rev the engine to 3000 rpm, and then take note of the voltage. It should hit the numbers between 13.8 volts to 14.5 volts. This is the minimum voltage needed to charge a 12V battery. If it doesn’t hit these numbers, there is a problem with your charging system.
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