An alternator and a battery work together in a vehicle’s electrical system, but they serve different purposes.

The alternator generates electricity to power the vehicle’s electrical systems and recharge the battery while the engine is running. It converts mechanical energy from the engine into electrical energy. The alternator also ensures that the battery remains charged, so it doesn’t lose power.

The battery, on the other hand, stores electrical energy and provides power to start the engine and operate electrical components when the vehicle is not running or when the demand exceeds the alternator’s output.

So, the alternator doesn’t take over the battery; rather, it works in tandem with the battery to ensure the vehicle’s electrical system functions properly. If the alternator fails, the battery will eventually lose power, leading to the vehicle’s electrical systems shutting down.

Several factors can lead to the failure of a car alternator:

1. Wear and Tear: Like any mechanical component, alternators can wear out over time due to the constant rotation of internal components. Bearings may wear down, brushes may become worn, and other internal parts can degrade, leading to failure.
2. Overuse or Overloading: If you frequently operate electrical components while the engine is not running or if you frequently demand high electrical loads (e.g., using high-powered audio systems, aftermarket lights, etc.), it can put excessive strain on the alternator, leading to premature failure.
3. Electrical Surges: Voltage spikes or surges in the electrical system can damage the alternator’s diodes, which are responsible for converting alternating current (AC) generated by the alternator into direct current (DC) used by the vehicle’s electrical system.
4. Corrosion or Contamination: Corrosion or contamination of internal components, such as the rotor or stator windings, can impede the alternator’s ability to generate electricity efficiently, leading to failure.
5. Belt Tension Issues: If the drive belt that connects the alternator to the engine is too loose or too tight, it can cause excessive wear on the alternator bearings and other components, leading to failure.
6. Heat: Excessive heat, often caused by poor ventilation around the alternator or operating in extreme temperatures, can degrade the alternator’s internal components over time.
7. Water Damage: Exposure to water or moisture can lead to corrosion of internal components, especially in alternators mounted low in the engine bay where they are more susceptible to water intrusion.

Regular maintenance, such as checking belt tension, inspecting for signs of wear, and ensuring proper electrical system operation, can help prevent alternator failure.