The replacement battery for tester is a rechargeable nickel-metal-hydride (NiMH) battery pack rated at 4.8 volts and 7,000 milliamp hours. It charges with the AC adapter included with the Megger BITE 3 tester.

Battery testers are used in the industrial, commercial, medical, telecommunications, aircraft, power utility, and military industries to detect the health of a battery. They can measure conductance, impedance, voltage, and current, among other parameters. Battery testers are designed for specific types of batteries, such as lead-acid, nickel-metal-hydride (NiMH) and alkaline batteries. Some testers require a load to be applied to the battery during testing, and some do not. A variety of test leads with contacts, probes, clamps, clips, and other connectors can be used to connect a battery to a tester. Since different testers can measure different parameters to calculate battery health, it is important to use the same tester for consecutive tests on a single battery when analyzing changes in battery health over time.