Which statement best describes a battery?

The statement that describes a battery as a device made of one or more electrochemical cells converting stored chemical energy into electrical energy is accurate. A battery functions primarily through electrochemical reactions, which define its ability to store energy chemically and then release it in the form of electrical energy when needed.

In a battery, the electrochemical cells consist of two electrodes (an anode and a cathode) separated by an electrolyte. When the battery is connected to a circuit, a chemical reaction occurs, allowing electrons to flow from the anode to the cathode, producing an electric current. This process is fundamental to how batteries work, making the correct statement not only relevant but essential to understanding the core functionality of batteries in various applications, such as powering electronic devices and electric vehicles.

The other options do not accurately capture the comprehensive nature of what a battery does or how it operates. A battery does not simply store energy without conversion, nor is it strictly a mechanical system or a unit that requires constant power to generate energy. This highlights the unique aspects of batteries that primarily depend on their chemical structure and the conversion process involved in energy release.