Signs of a Bad Car Battery vs. Alternator
Determine if your car battery or alternator is the root of your car troubles, plus how to fix the issue.
Written by Alexandra Maloney
Reviewed by Kathleen Flear
It’s a tale as old as time—you’re running late, hurriedly jump into your car, and turn it on ready to go. The only problem? You’re met with a car that won’t turn on, or a slew of strange noises like clicking, sputtering, and banging that make you more than a little concerned about hitting the road.
If you’ve found yourself in this situation, the problem you’re facing more than likely revolves around your
car battery
or alternator. But, it can be hard to even know the difference between the two, nevermind which is causing the problem and how to fix it. In this article, we’re breaking down everything you need to know about failing car batteries and alternators, so you can be well equipped to address the problem and repair your car
next time. 
Car battery vs. alternator
To know the signs of a bad car battery or alternator, it’s important to first understand what they are and the role they play within your vehicle.
In a nutshell, a car battery is the thing in your car that’s responsible for turning it on. It works by sending an electrical current to the starting motor every time you turn the key in the ignition or push to start. The starting motor then sends that message to the engine, which powers your car.
The alternator supplies power to the battery and charges it. While the battery is responsible for turning your car from off to on, the alternator supplies power while your car is running to systems like the
headlights
, windshield wipers
, dashboard instruments, heated seats, and more.Signs of a bad car battery
Now that you know the difference between a car battery and alternator, let’s take a look at some signs the battery might be causing your car trouble. Here are some of the most common signs to watch out for, according to
Tire Plus
, that indicate your battery is in trouble.- Clicking sound when turning the key in the ignition.
- Slow engine crank.
- Need to press the gas pedal in order to get the car to start.
- Backfiring (sparks) coming from the hood of your car.
Plus,
Roadway Ready
urges drivers to look out for a smell of rotten eggs, the battery light being on, or the radio losing its presets as further signs your car battery is failing. Signs of a bad alternator
If none of the signs above sound like issues you’re having with your car, the alternator might be the root cause of your car troubles. Here are a few indicators that you have a bad alternator, according to
Firestone Complete Autocare
. - Dim or overly bright headlights.
- Trouble starting or frequent stalling while driving.
- Slow or malfunctioning accessories (like automatic window controls, heated seats, etc.)
- Smell of burning rubber.
- Issues with the sound system.
- Car won’t start at all.
What to do next
Once you’ve identified either the car battery or alternator to be the problem with your car, the next step is to get the issue resolved. For a car battery, if you suspect it might be dead, try jump starting it with the help of another car. If a jump gets your car up and running, drive around for at least 20 minutes and make sure no problems persist. Additionally, monitor your car over the next few weeks.
If jump starting your car doesn’t work, it could mean you need a replacement battery, which means you’ll need to take your car to a professional. Battery age is the most common cause of car battery issues.
If you suspect the alternator is the issue, you can try to jump start the car, but it likely won’t be a long-term solution. In this case, bringing your car to a professional is likely the best course of action to safely drive again.
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