Which device prevents overcharging of the battery?

The device responsible for preventing overcharging of the battery is the voltage regulator. The voltage regulator plays a critical role in managing the voltage output from the alternator, ensuring that it remains within a safe range for the battery. When the alternator generates electricity, the voltage regulator monitors the battery voltage and adjusts the alternator's output accordingly. By doing so, it prevents excessive voltage from reaching the battery, which can lead to overcharging, overheating, and potentially damage the battery.

In contrast, the other options serve different functions in the electrical system. The alternator stator is involved in generating electrical power, while the battery monitor provides data about the battery's condition but does not actively control charging. A battery fuse serves as a safety device that protects the circuit from excessive current, but it does not regulate the voltage or prevent overcharging. Thus, the voltage regulator is the key component that ensures the battery is charged safely and efficiently.