Batteries in cars and trucks are typically only used to start the vehicle, but when your battery is no longer holding a charge or is acting up, taking the car to a shop that offers battery testing is one place to start. Often the test can be done in the vehicle, and some places will do the battery testing free of charge while you wait.
Car battery testing is not difficult to do if you have the testing equipment to do the job. A multimeter can tell you if you have twelve volts of power in the battery, but it will not tell you much more than that.
To properly test an automotive battery, a tester designed to read the voltage and test the battery's condition needs to be used for an accurate test. Most repair shops and many auto parts stores have the equipment to test your battery correctly, and they can do it without removing the battery from the car in most cases.
The battery testing starts with a test of the voltage, and then the analyzer load tests the battery to mimic what happens when you turn the key on the ignition. The battery should respond with enough power to turn over the engine, but it will often fail this test if the battery requires replacement.
Sometimes a battery that is not charging correctly will struggle during the battery testing. The shop may need to charge the battery on an external charger before getting an accurate test result. If the battery is not fully charged, it can be a sign of a bad cell in the battery or a charging system that is not correctly charging the battery when the car is running.
Charging the battery then testing it will determine which is the case, and if the battery is bad, it may not take a charge at all. Once the charging is complete, the tech can then test the battery again, and if it is still not producing the required amps to turn over the engine, it is likely time to replace the battery with a new one.
It is essential that the car battery testing is done out of the car if the battery fails the first test or that the tech removes the cables and cleans the terminals on the battery before charging and testing. A dirty terminal with a poor connection can mimic a bad cell in the battery and make it hard to get an accurate test result.