Common Causes of Voltage Instability During Vehicle Acceleration

Voltage instability during vehicle acceleration can be caused by several factors, including battery damage, aging, poor connections, failure of the generator voltage regulator, internal faults in the generator, and belt issues. When these factors interact, the voltage instability phenomenon becomes noticeable.

1. Battery Issues

• Battery Damage: The vehicle battery can be damaged if it frequently experiences high residual currents, which can cause voltage instability. For example, frequent car starts can drain the battery, and over time, this can reduce its ability to maintain stable voltage.
• Battery Aging or Low Charge: As a battery ages, its ability to convert chemical energy into electrical energy decreases. If the battery charge is insufficient, it may fail to maintain stable voltage. Normally, a 12V car battery will have a full charge voltage of about 13 volts, and under load, a voltage greater than 11 volts is considered normal. If it falls below this, voltage instability may occur.
• Internal Battery Poor Connections: If the internal components of the battery, such as the plates or terminals, become loose or corroded, poor contact can result. During vehicle acceleration, the sudden demand for electricity can make the voltage instability more noticeable. For example, in older vehicles, the battery terminals may develop white oxide, which can interfere with current flow and cause voltage instability.

2. Generator-Related Issues

• Voltage Regulator Failure: The voltage regulator plays a crucial role in adjusting the generator’s output voltage. If the voltage regulator fails, the generator cannot output a stable voltage during vehicle acceleration, leading to voltage instability. For example, if components like field-effect transistors or Darlington transistors in the regulator are damaged, the excitation current may become uncontrolled, causing abnormal voltage output.
• Internal Generator Faults: Faults in internal components of the generator, such as windings or rectifier diodes, can also lead to voltage instability. For example, a short circuit in the windings or a breakdown of a PN junction in a rectifier diode can affect the generator’s efficiency, leading to voltage fluctuations.
• Belt Issues: After the engine is started, the generator is driven by a belt. If the belt is worn or slipping, it can reduce the generator’s efficiency, resulting in voltage instability. This is especially true for vehicles that have not had their belts checked for a long time. Over time, belts can wear out, crack, or break, affecting the generator’s normal operation.

3. Electrical Circuit Issues

• Loose Circuit Connections: The vehicle’s electrical system is complex, and poor connections in the circuit can cause voltage instability during acceleration due to the rapid changes in current demand. For example, if the wiring is loose or has poor contact, it could create intermittent power supply issues, which may cause voltage fluctuations, especially when the engine speed increases during acceleration.