How to check the voltage of a car battery
Few things are more frustrating than finding your car won't start due to a dead battery. A mechanic can measure the voltage in a battery to determine if it needs to be replaced. There is…
Few things are more frustrating than finding your car won't start due to a dead battery. A mechanic can measure the voltage in a battery to determine if it needs to be replaced. There are two ways to do this.
Open circuit voltage test
This car battery test determines how fully charged your battery is. This test is done twelve hours after the car is turned off to allow any surface charge to dissipate. This means more accurate reading. The test is carried out with the engine off. Then your mechanic may use a multimeter/voltmeter or a dedicated battery tester. A special tester is simply connected to the battery terminals, and the voltage can be read. With a multimeter, the device is set to measure voltages up to 20 volts. The wires are then connected to the battery terminals, positive to positive and negative to negative, to get the voltage.
A reading of 12.65-12.77 volts means your battery is fully charged. 12.45-12.54 volts means you are 75% charged, 12.24-12.29 volts is 50% charged, and 11.99-12.06 volts is 25% charged. 11.75-11.89 volts means your battery is dead.
Electrolyte gravity stress test
This method is used for leaky lead-acid batteries. With this method, the hydrometer measures battery voltage. A specific gravity of 1.269 means the battery is fully charged. A value of 1.229 indicates 75% charge, 1.194 indicates 50% charge, and 1.159 indicates 25%. 1.124 means your battery is dead.
Load test performance and capacity
This type of car battery test measures the battery's ability to produce current. Before doing this test, AvtoTachki will test the car battery to make sure it is at least 75% charged. The voltage of the battery is then measured under a load similar to that required to start the car. He or she will then use a special load tester—a large resistor with a resistance very similar to your car's starter motor, and a meter that reads the output voltage—to apply a load equivalent to ½ of the engine's cold cranking current rating. batteries for about 15 seconds. You should expect a reading of at least 9.1 volts.
Check your car battery regularly. You should check your car battery at least once a year, preferably when the cold starts.
