The Garage Car Care

Why Is Your Battery Light On and What Does It Mean?

It's the check engine light's wicked cousin.

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When you turn the car on, its dashboard briefly lights up like an overcrowded fast-food menu. An array of illuminated numbers, letters, indicators, read-outs, and symbols flash and quickly fade to black. If there’s an issue with the vehicle’s charging system, however, the little battery light will remain on with the intense glare of a kangaroo mob.

Although a battery-shaped light suggests a battery problem, reality is more complicated. The issue could simply trace to the battery or its terminals, but it could also be the result of a failing alternator, a bad connection, or a number of other issues.

Regardless of the problem, a bad charging system will drain the battery and cost you money, so you’ll want to address it immediately. To figure out the cause of your battery light’s unexpected appearance, The Drive’s die-hard informational team has laid out a guide to identifying, diagnosing, and solving your car’s problems. 

Yippee ki yay, let’s get into it!

What Is the Dashboard Battery Light and What Does it Do? 

The dashboard light shaped like a rectangular Lego-looking battery is officially known as the Charging System Light, and this refers to traditional combustion vehicles, not electric vehicle charging. If the light stays on after turning the vehicle on or lights up while driving the vehicle, it’s a warning to the driver that the charging system is not running efficiently enough to properly charge the battery while maintaining power to necessary accessories.

If you notice your charging system light on your dashboard, immediately drive home, to a local dealership or garage, or a local auto parts store using only backroads, not the highway.

What Is a Car’s Charging System?

A modern vehicle’s charging system, which functions to keep the battery charged, includes a battery, wiring, an alternator, and the electronic control unit (ECU). Older vehicles also had a voltage regulator.

Alternator: The alternator accepts mechanical energy from the engine and turns it into electrical energy to power accessories and charge the battery.

Battery: The battery provides energy to start the vehicle and to power its electronics.

ECU: The electronic control unit, not to be confused with the engine control unit, is a device that manages the linked electronic system. It regulates where, when, and how power is held or flowing.

A multimeter is a crucial testing tool for diagnosing car batteries.
Three types of electrical testers., DepositPhotos

Why Is the Battery Light On?

There are a multitude of reasons why the charging system is not operating at maximum capacity. Let’s go over what they could be.

Bad Electrical Connections

Check all connectors for corrosion and proper seating. Retighten, if necessary.

Slipping or Faulty Serpentine Belt

The serpentine belt is the piece of reinforced rubber that turns the alternator’s pulley and powers the alternator. If the belt isn’t properly running the alternator, it could create charging issues.

Battery Terminal Disconnected

Check the battery terminals to make sure the cables are correctly connected. If a wire is disconnected, clean the terminals, reattach the cable to the battery, and tighten.

Battery Terminal Corrosion

Check the battery terminals for corrosion that could be creating an inconsistent connection. Visit The Drive’s guide for How To Clean Battery Terminals for more.

Battery Dead

Use a multimeter to test the battery for the correct voltage. A fully charged battery should register 12.6 volts or more. If it’s off, try recharging the battery with a trickle charger before replacing it. Visit The Drive’s guide for How To Change a Car Battery for more.

Bad Alternator

Use a multimeter to test the alternator. It should read between 13.8-14.2 volts. If the voltage is below normal, the alternator might need to be replaced.

Use a multimeter when checking battery voltage.
Checking battery voltage., DepositPhotos

Other Symptoms You Might Notice

Although a charging system light is the easiest way to notice something is wrong, there might be accompanying symptoms that could tip the problem prior to the light’s illumination or provide more information as to why the light turned on in the first place. These symptoms, which are unfortunately similar across all three parts, could indicate the bigger issue:

Symptoms of a Bad Alternator 

  • Metal grinding, rumbling, or whining noises
  • Accessories won’t power on
  • Dim or inconsistent headlights
  • Car won’t start

Symptoms of a Bad Starter

  • Clicking noise when turning the ignition
  • Slow engine crank
  • Grinding noise after car starts
  • Car won’t start

Symptoms of a Bad Battery

  • Dim or inconsistent headlights
  • Dim interior lights
  • Interior lights turn on but car won’t start
  • Literally nothing on the car works

Get Help With Fixing the Dashboard Battery Light From a Mechanic On JustAnswer

The Drive recognizes that while our How-To guides are detailed and easily followed, a rusty bolt, an engine component not in the correct position, or oil leaking everywhere can derail a project. That’s why we’ve partnered with JustAnswer, which connects you to certified mechanics around the globe, to get you through even the toughest jobs. 

So if you have a question or are stuck, click here and talk to a mechanic near you. 

Corroded battery terminals need to be cleaned for the battery to function properly.
Battery terminal corrosion., DepositPhotos

Battery Light FAQs

You have the questions, The Drive has the answers!

What Does It Mean When the Battery Light Comes On?

It means there’s an issue with the vehicle’s charging system, which includes the battery, the alternator, the wires, and the ECU.

Is It Safe to Drive My Car With the Battery Light On?

If something in the vehicle’s charge system isn’t functioning properly, there is risk of the car shutting off without warning. It’s also possible that if the vehicle dies, it might not be possible to start it back up. Because of this, we do not recommend or suggest driving with the battery light on to any place other than back to your house or a service center. If the light comes on before driving, we do not recommend driving.

What Do You Do When the Battery Light Comes On? 

Slowly drive your car home, to a service center, or to an auto parts store. Then, diagnose and fix.

How Can You Tell If It’s the Battery or the Alternator?

Use a multimeter to check the voltage on both the battery and alternator to verify they’re functioning at the correct levels.

Will a Car Start With a Bad Alternator? 

It is possible for a car to start with a bad alternator, but it will likely immediately die.

Featured Diagnostic Products

Ancel Classic Enhanced Universal OBD II Scanner

Equus Auto-Ranging Digital Multimeter

Fastronix Military Spec Battery Terminal Top Post Kit

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Tony Markovich Avatar

Tony Markovich


Tony Markovich is a former Senior Editor at The Drive, departing in 2022.