What are the causes of auxiliary battery failure in vehicles?
2 Answers
To determine the specific cause of auxiliary battery failure in vehicles, it is necessary to understand the meaning of the fault code. The auxiliary battery generally refers to the battery that powers the entertainment system, windows, doors, and lighting system during startup. For auxiliary battery failure, the meaning of the fault code must be analyzed for repair. Possible causes include low battery voltage, battery damage, or even faults in the wiring and control circuits. It is recommended to visit a repair shop for an initial inspection. The auxiliary battery can be viewed as a large capacitor. On one hand, it supplies power to systems like entertainment and lighting during the instant of engine startup, when the engine is not running, or during low-speed operation. On the other hand, it assists the main battery in supplying power when there are too many electrical devices or high power consumption. Additionally, it plays a role in stabilizing voltage by absorbing instantaneous overvoltage in the circuit to protect electrical devices.
Last time I had my car repaired, I encountered a hybrid vehicle with an auxiliary battery failure, and several common causes were identified. First, the battery itself was aging, especially after four or five years of use, with a significant drop in capacity. Second, there was an issue with the charging system, such as loose wiring connected to the DC-DC converter or a faulty converter, preventing the auxiliary battery from charging properly. Third, over-discharge was a factor—some people forgot to turn off the headlights or audio system after parking, draining the battery completely. Additionally, extreme weather conditions played a role; high summer temperatures accelerated battery degradation, while winter cold reduced battery performance. To determine the specific cause, it’s essential to first use a diagnostic tool to read the fault codes, focusing on whether the DC-DC output voltage is stable, and then test the battery’s health. If it’s just poor contact, it’s easier to fix, but if the battery is completely dead, replacement is the only option.
