Final answer:
The Voltage regulator in a three-unit control panel is responsible for preventing overcharging of the battery by maintaining a consistent voltage level.
Step-by-step explanation:
The component in the three-unit control panel that prevents overcharging of the battery is the Voltage regulator. The voltage regulator's role is to maintain a consistent voltage level to the battery, ensuring that the charging process stops when the battery reaches its full capacity. This component prevents damage to the battery that can result from overcharging.