A battery load tester is a device that can test lead-acid batteries, and charging and starting circuits found on most cars, motorcycles, cars, light commercial vehicles, and other small vehicles. Battery load testers can only be used if the battery is at least 75% charged.

One method of carrying out a battery load test is as follows. Turn the headlights on for six minutes, then disable the ignition and turn the engine over for 15 seconds with the starter motor. Using the battery load tester, apply a load equal to one half of the cold cranking amps (CCA) rating of the battery, or one half the original equipment manufacturer (OEM) cranking amp specification. During the load test, the voltage on a good battery should remain at or above 9.7V with the electrolyte at 80 degrees F. (If the electrolyte is above 80 degrees F, add 0.1 volt for every 10 degrees above 80 up to 100 degrees; below 80 degrees, subtract 0.1 volt for every 10 degrees down to 40 degrees.) After the load is removed, the battery should return to the 50% state-of-charge level or above. If the battery drops below minimum test voltage, does not bounce back or will not start the engine, then it needs replacing. If the battery passes the test, it should be recharged to restore it to peak performance.