Why the car battery light comes on when driving

The dashboard is an interface between the vehicle and the driver. Aside from focusing on the road ahead, the driver monitors the dashboard to identify if any component is failing. Should drivers be worried when the battery light is on in a car? 

The car battery plays a pivotal role in its operation. Battery lights can come on anytime when driving. Several things cause the light to come on. When igniting the vehicle, the light comes on and disappears after the engine comes on. It should not be a cause of concern to the driver. The following reasons require the attention of the driver.

Damaged battery

Ordinary car batteries last an average of 3 to 5 years. The battery has a cathode and anode that are submerged in an electrolyte. After several years of use, the anodic and cathodic plates deteriorate. The broken cells allow leakage of the electrolytic solution. When this happens, the battery light comes on. The remedy for this is to replace the battery.

Faulty alternator

Car alternators deliver 13.6 to 14.6 volts to recharge the battery when driving. If the alternator is damaged, it supplies low voltage (lower than 12V). The low voltage causes the battery light to come on. 

Loose or broken alternator belt

The alternator belt connects the engine and the alternator. The belt is subjected to friction at the pulleys. It causes the belt to weaken. In some cases, it becomes too tight. The variation in belt tension causes slight misalignment. If this is the case, the belt squeals when the engine runs and causes the battery light to come on.

Corroded battery terminals

When the battery terminals corrode, electrical connections become loose. The corroding terminals cause weak electrical connections that trigger the appearance of battery lights on the dashboard.

Poor battery wiring

Cars rely on wires to transfer electric energy from the battery to diverse electrical components. The wires run to the terminals. If the wiring connections are loose, the battery light comes on.

Bad grounding

Vehicles use a grounding strap to complete the electrical circuit. A faulty or loose grounding strap causes an incomplete electrical circuit. The battery cannot recharge. If the strap is damaged, then the battery light will come on. It indicates that the battery is not charging.

Rapid discharging of the battery

Modern vehicles contain several components that draw power from the battery. When driving, the components draw energy from the alternator. When several accessories are in use at once, power consumption is high. The accessories use excess power starving the battery of electric charge. It triggers the battery light signal.

Faulty wiring

Charging the battery relies on multiple wires. When these cables are loose, battery charging quality is low. The battery light signal comes on if the wiring is faulty. 


Drivers must pay attention to dashboard lights when driving. When the battery light comes on in a car, the driver should troubleshoot the root cause of the signal. Replace the battery if it has outlived its service life. Fix any loose connection, replace the alternator belt or repair faulty components of the charging system.