how to test a battery

Testing a battery is not rocket science, but it does require some common sense and a voltmeter. First, ensure the battery is fully charged and disconnected from any device. Then, measure the voltage across its terminals; a healthy 12V car battery should read around 12.6 volts or more. If it dips below 12.4 volts, it’s time to worry. For a more rigorous test, perform a load test by applying a load equal to half the battery's Cold Cranking Amps (CCA) rating for 15 seconds and watch the voltage drop; it shouldn’t fall below 9.6 volts. Always wear safety goggles and gloves because battery acid is a sadistic little beast. For more detailed procedures, consult a manual or ServiceCentral.