Why Battery Voltage Drops While Driving

The battery powers all the electrical components in your vehicle, including everything from the LED lights to your air conditioning unit. The battery voltage indicator on the dashboard helps us keep an eye on the battery’s condition while we drive. Therefore, a sudden voltage drop while driving is concerning, which prompts the question of what causes the battery voltage to drop? and why does it occur while driving?

Battery voltage drops while driving when the battery can’t supply enough power to run the car’s electrical parts. A drop in battery voltage while driving occurs when there’s a problem with your car’s battery or the battery’s charging system. 

This article will discuss the factors that cause a drop in battery voltage, how you can prevent each or fix each one, and what your battery voltage should be while driving.

What Causes Voltage Drop

Voltage in an electric circuit drops when resistance builds up and impedes current flow. Even without looking at the battery gauge, you can easily observe an excessive voltage drop in different electric parts. A good example is headlight flickers, dim LED lights, or interference when the radio is turned on.

Because of the different components in a car’s electric system, the voltage drop you experience while driving can be due to several factors. Some of the most common causes of voltage drop while driving are:

Bad Alternator

The alternator is at the core of a car’s charging system. It is responsible for converting mechanical energy from the car engine to electrical energy that powers the electric components of the car. Therefore, while you drive, the battery starts getting recharged by the alternator.

Alternators are integral components of gasoline-powered vehicles, and it is often attached to the engine itself. The alternator is responsible for charging your car’s battery while you drive. Alternators are rarely a cause of concern in car maintenance. However, it is the leading cause of voltage drop while driving.

Since the alternator charges the car battery, when it is damaged or stops working, the battery gauge drops accordingly. This does not happen immediately as the car can still run on the charge left in the battery.

Bad Serpentine Belt

Another point of failure associated with voltage drop and the alternator is the serpentine belt that drives it. The serpentine belt rotates the alternator in its energy conversion for electrical uses. A ragged or broken serpentine belt will be unable to provide the rotation needed for the alternator to generate electrical energy — resulting in a voltage drop.

An easy way to detect a problem with your alternator is through the battery icon situated near the battery gauge on your car’s dashboard. Usually, this icon turns red when you start the ignition, but as the car starts driving and the battery starts getting charged, the lights go off. A persistent red color of the battery icon indicates a problem with your alternator.

Battery Corrosion

All batteries are susceptible to corrosion over time. A key part of battery design is the presence of small vents that allow by-product gasses to escape into the atmosphere. These gasses often contact battery terminals, gradually wearing them down. Severely corroded terminals will not be able to receive sufficient charges from the alternator, and the battery remains uncharged. 

The results of a corroded battery are the same as that of a bad alternator. In both cases, the battery cannot charge, and the battery voltage drops as the remaining charge on the battery is used up when you start driving. You can check your battery for corrosion by opening the hood. The corroded terminals and wires connected to the battery develop a white, blue, green, or brown-colored deposit that is flaky. It may also appear as rust. 

You can usually clean battery corrosion with battery cleaner and a brush. Baking soda also works if you don’t have immediate access to a battery cleaner. However, because of the persistent nature of battery corrosion, you will have to carry out the cleaning process regularly. Once corrosion sets in, the battery is also affected. And the damage starts getting accumulated until you might have to change it.

Loose Electrical Connections

Shaky and slack electrical connections to the battery are another common cause of voltage drop while driving. However, it is more subtle and can be hard to detect. 

Electrical connections in a moving vehicle will start slacking gradually. Poor connections might not be easily noticeable at first, but the connection continues to lose its attachments over time. Eventually, these parts disconnect from the battery and hinder the transfer of electric charge from the battery. Loose connections can also happen from poor connections made during maintenance.

Loose connections cause a build of resistance in the flow of current that leads to a drop in voltage. These poor connections lead to the inefficiency of the battery charging system and cause a decrease in the amount of usable power that reaches the battery.

You can prevent loose electrical connections and the associated voltage drop while driving by ensuring tight and secure connections.

What is Battery Voltage?

Battery voltage measures the rate at which electric current is transferred from your battery. The battery gauge or battery indicator measures the battery voltage and helps you keep track of the condition of your car battery.

Battery voltage is measured in volts and indicated on the battery gauge. Battery gauges graduations range from 10 – 16 volts, with an indicator alternating between these digits. 

What Should Your Battery Voltage be While Driving?

A car with a fully working electrical system and the battery should measure between 13.7 volts and 14.7volts while driving. A fully charged battery will have a voltage of 12.4 volts to 12.8 volts when the car is at rest. A car battery voltage between 11.75 and 11.89 volts indicates a dead battery that you might need to replace.

Low voltage can easily damage your car or confuse you while you drive. You might notice electrical parts of the car like the AC unit or the radio start malfunctioning. A flickering headlight can also put you at risk when driving at night.

The alternator can also be affected when you continue running the electric parts of the car with a low voltage. The damaged alternator will then become another expense for you when you find the source of the problem.

Therefore, you should pay attention to a drop in battery voltage. Check your battery icon indicator for warnings. And ensure your car’s charging system and battery are in good condition with an adequate voltage supply while driving.