What is the primary function of the battery in a vehicle's electrical system?

The primary function of the battery in a vehicle's electrical system is to store electrical energy. The battery provides the necessary electrical energy to start the engine and powers various electrical components and systems when the engine is not running. This stored energy comes from the battery's chemical processes, which convert chemical energy into electrical energy when needed.

While generating electricity, acting as a relay, and regulating voltage are important aspects of an electrical system, these roles are typically performed by other components. For example, the alternator generates electrical power while the engine is running, and voltage regulators manage the voltage and current coming from the alternator to prevent overcharging the battery. Similarly, relays are used to control the flow of electricity in various systems but do not directly involve the battery's primary function. Thus, the correct answer highlights the essential role of the battery in energy storage within the vehicle's electrical system.