Bad Battery vs. Bad Alternator

Bad Battery vs. Bad Alternator
Published: Mar 9, 2011
Updated: Nov 20, 2021
2 minute read

Bad Battery Signs

replacing a car battery

The easiest way to know you have a bad battery is when the battery light illuminates on the dashboard while you are driving. The sign of a dead battery is obvious when you get in a vehicle, insert the key in the ignition and turn the key. You will hear nothing at all when the battery is dead. If the battery is bad but is in danger of going dead, you will hear a clicking sound when you turn the key. Also, conduct a visual test of the battery under the hood, looking for corroded leads or split wires, which can indicate a bad battery.

Bad Alternator Signs

replacing an alternator

Outside of spotting an illuminated dashboard light indicating a problem with your automobile's charging system, you can diagnose a bad alternator in other ways. If the automobile won't start, turn on the headlights. If the headlights shine brightly, that can be the first indication of a bad alternator. Next, turn the key in the ignition to try starting the car. If the lights continue shining bright while you do this, but the automobile won't start, the problem is likely a bad alternator. If you are driving with the headlights on and the lights dim when you slow down, this also indicates a bad alternator.

Advertisement

Bad Alternator and Bad Battery Effects

A bad alternator will not charge your battery

Depending on how much electricity an automobile requires, it can run for a short time if it has a bad alternator. The alternator's job is to recharge the battery while you're driving once the battery has started the car. A bad alternator will not properly charge the battery. Also, if the battery itself is bad, an alternator in working order won't be able to charge it.

Replacement

Replacing an alternator is not hard.

When you replace a bad alternator, you can install a rebuilt alternator in the automobile that will work as well as a new alternator. Because the alternator is usually located in an accessible spot on top of the engine, it is normally a light task. A properly working alternator can often recharge a dead battery by running the automobile for a period of time. You can also charge up a dead battery with a battery charger. When you change out a bad battery, be sure to obtain a replacement that has the cold cranking amps that your auto needs.

The Drip Cap

  • Because the alternator and the battery are both components of an automobile's charging system, the operation of one affects the other.
  • If the lights continue shining bright while you do this, but the automobile won't start, the problem is likely a bad alternator.
  • A bad alternator will not properly charge the battery.
  • Also, if the battery itself is bad, an alternator in working order won't be able to charge it.
  • When you replace a bad alternator, you can install a rebuilt alternator in the automobile that will work as well as a new alternator.

Photo Credits

Hemera Technologies/AbleStock.com/Getty Images

Hemera Technologies/AbleStock.com/Getty Images

Joe Belanger/iStock/Getty Images

venturecx/iStock/Getty Images

Zeljko Radojko/iStock/Getty Images

susaro/iStock/Getty Images

Christopher John

Christopher John has been a freelance journalist since 2003. He has written for regional newspapers such as "The Metro Forum" and the "West Tennessee Examiner." John has a Bachelor of Arts in journalism from Memphis State University.

Sponsored
HomeSteady Logo

HomeSteady is the ultimate guide for all your household needs, from cleaning and HVAC to electrical, DIY and maintenance.

Property of TechnologyAdvice. © 2026 TechnologyAdvice. All Rights Reserved

Advertiser Disclosure: Some of the products that appear on this site are from companies from which TechnologyAdvice receives compensation. This compensation may impact how and where products appear on this site including, for example, the order in which they appear. TechnologyAdvice does not include all companies or all types of products available in the marketplace.