Abstract: The authors consider accumulator batteries of mobile communication facilities. Battery self-discharge depends on the quality of the materials used, the technological process of production, the type, and the construct of the accumulator. It increases sharply with the increase of environmental temperature and upon the internal separator damage in the result of inappropriate service or aging process. Rechargeable or accumulator batteries are more popular among the final consumers, and their production is one of the most dynamically developing sectors of the economy. It promotes consumer services competition; therefore, the problem of creation of an express-testing device for accumulator batteries is urgent. Unlike the imported devices, it will have low cost-price and comply with all repair and service requirements. The research methodology is based on the fact that accumulator capacity reduces while in operation. The reduction speed depends on the type of electrochemical system, the service technology, the battery chargers used, and conditions and terms of exploitation. Accumulator’s internal resistance (current source resistance) determines its ability to give up heavy current. Its dependency obeys Ohm’s law. At law rates of internal resistance, an accumulator can give up heavier peak current (without significant reduction of terminal voltage), and, consequently, the bigger peak power; while high resistance leads to sharp reduction of peak power at sharp reduction of load current. Internal resistance of an accumulator depends on its electrochemical system type, capacity, number of cells connected in series, and increases by the end of its life. The authors have designed the hardware component of a device for accumulator batteries express testing. The device can be used in authorized service centers and electronic stores.