Why is the battery not charging?

[StCody]

Here are the reasons why a car battery may not charge: 1. Deep discharge: When the vehicle is turned off, the onboard devices remain in operation, continuously consuming the battery's power. Prolonged use under such conditions can accelerate the battery's degradation, leading to failure in charging. Therefore, always ensure electronic devices are turned off when parking. 2. Generator belt aging: The engine directly drives the generator via a belt, which after rectification and voltage stabilization, charges the battery. If the belt malfunctions, it can prevent charging, necessitating timely replacement.

[Pierce]

I've been driving for over 20 years and often encounter battery charging issues. Once, after starting my car, the charging light stayed on. Upon inspection, I found the alternator belt was a bit loose—insufficient tension meant the alternator couldn't spin and thus couldn't charge. Alternator failures are also a major cause, such as a faulty internal rectifier leading to unstable output, or voltage regulator issues causing the alternator voltage to be too high or too low. Another common issue is an aging battery—after five or six years, increased internal resistance can prevent proper charging. Don’t forget to check the fuses; a blown charging circuit fuse will cut off the current. A simple DIY test: start the car and measure the alternator output with a multimeter—it should read 13-14 volts normally. Always keep an eye on dashboard warning lights; if they come on, avoid long drives and head to a repair shop promptly to avoid being stranded. For maintenance, regularly check belt tension and clean battery terminals to prevent bigger problems.