Do You Have to Replace Battery When Replacing Alternator

Published on: August 5, 2022
Written by Liam Jaxon / Fact-checked by David Rowan

Do you face that time when you get that gut feeling that there’s something wrong with your car? There’s that sinking fear that your car will suddenly stop working in the middle of the freeway in the middle of the afternoon when you have to take it to the mechanic in the next town.

If so, you may be suffering from a bad alternator. One of the most important parts of your car, an alternator, keeps your vehicle running when the battery runs low. If it fails, you find yourself in the middle of the freeway in the middle of the afternoon with no power to your car.

do you have to replace battery when replacing alternator

Every time you change your car’s battery, your vehicle’s alternator goes with it. But do you have to replace the battery when replacing the alternator? Maybe not. Often, it’s not necessary to replace both at the same time. That is because the alternator itself can be removed, and the battery can check. You can test without replacing it because it’s possible to determine the battery’s condition by measuring the battery’s state of charge.

But if you have an older battery then you shouldn’t take a risk. We recommend that when you change your alternator then you should change your old battery. Read below what you should do with your bad alternator.

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Should the Battery Need to Be Replaced Whenever an Alternator Is Replaced?

The battery in a car is a vital part of the electrical system, and an alternator is a vital part of its performance. When a car’s alternator fails, it must replace, but not if the battery itself is the cause of the problem. 

It’s important to note that there are several instances when a car’s alternator could be damaged. In one of them, a car’s alternator fails, but the battery does not. In this case, you should replace the alternator, but the battery does not need to be replaced. 

But if you feel your battery is older or having some problems then it is better to replace it with a new one.

8 Symptoms of a Bad Alternator

Want to know what symptoms you should look out for if you suspect that your car’s alternator might be faulty? Here’s a quick, simple, and to-the-point guide to checking and repairing your car’s alternator:

1. Dead Battery: 

If your car battery is dead, it doesn’t necessarily mean that your alternator is malfunctioning. A battery can die for various reasons, and the only way to tell for sure is to replace it.

If you’ve got a car that’s eight years old or less, that means replacing your battery every eight years. If you’ve got a car that’s older than eight years, though, you’ll have to replace it every eight years as well. Because a bad battery will have a bad effect on your alternator.

2. Dim or Bright Light: 

It can be frustrating when you notice that your car’s headlights are either too dim or extremely bright. When you have tried to adjust your headlights to the level, they are designed to be. They are still either too dim or extremely bright. 

Or you have tried turning your headlights on and off, but they are still either too dim or extremely bright. It is the symptoms that your alternator gets problems with.

3. Slow or Dead Accessories:

If you’ve ever sat in a car that didn’t start, you’ve probably wondered what the heck is wrong. Well, if your car is seized, it won’t start a lot of times. The cause is the alternator. Another cause is slower dead accessories on your cars.

4. Bad Belts: 

A bad belt is the amount of tension needed to hold the belt’s mating pulleys to the engine. If there’s too much tension, it can damage the alternator, weakening the belt over time. Heaving a bad belt will start to break apart and can eventually pop off. And it also badly affects your alternator. As a result, this is a sign that it’s time to replace the alternator.

5. The smell of Burning Rubber:

As always, the smell of burning rubber is the cause when you need to replace your alternator. Because when you smell burning rubber, it means that your alternator is not functioning properly. With it not working, your car would overheat and catch fire.

do you have to replace battery when replacing alternator
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6. Make Whirring Noises From the Engine: 

Your car’s alternator develops a new whirring and buzzing hum noise. Suddenly if you’ve noticed a noise, which comes from under the hood of your car. Firstly find its source before bringing it to the service center. If it’s because of the alternator, then you may be able to disassemble it. 

7. Turns On the Battery Warning Lights: 

If the battery warning lights are caused when you need to replace your alternator. When your car’s charging system is experiencing a severe issue, the engine computer may detect the problem and alert you with a dashboard warning light. This light may look like a battery, or the light may say “BATT” or “ALT” to indicate a problem with the charging system.

8. Loose Connection: 

In this case, everything with your car’s alternator seems to check out ok, no belt issues or other visible signs of trouble — but the car’s battery is dead, as is most of the car’s electrical equipment. That might mean that the alternator is producing electricity, but it’s not going anywhere, or it’s not the right type.

Alternator electricity is piped through large cables and smaller wires. Any problems within the wires or loose or broken cable connections at either end can reduce or stop electricity from getting through.

How Much Does It Cost to Replace an Alternator Battery?

The cost to replace the battery will vary depending on the replacement battery you purchase to replace the battery in your car or truck. Whether you have to have it replaced at a dealership or not, and where you live.

For example, if you have to replace the alternator battery at a dealership, the dealer will charge you for labor, parts, and warranty work. If you have to replace the alternator battery at an independent shop, the shop may charge you for the labor to replace the battery, but not for parts or warranty work.

Are There Any Special Tools or Procedures Needed When Replacing an Alternator?

Yes, there are some special tools and procedures that may be required when replacing an alternator. Some of these may include a socket set, a belt tensioner tool, and a multimeter to test the alternator’s output. Additionally, it may be necessary to disconnect the battery and remove various components such as the drive belt and mounting bolts in order to access the alternator. It’s important to consult the vehicle’s service manual for specific instructions on how to replace the alternator, as the process can vary depending on the make and model of the vehicle.

Will Upgrading to a Deep Cycle RV Battery Impact the Need to Replace the Alternator?

When upgrading to a deep cycle RV battery, you may experience a decreased need to replace the alternator. A reliable power source like a deep cycle battery can provide consistent energy for longer periods, potentially reducing the strain on the alternator and prolonging its lifespan.

What Should You Do When the Alternator Needs to Be Replaced?

Today’s vehicles have a 12-volt battery that provides electrical power to your car’s electrical system. The alternator provides that power to the battery for ready use when the engine is running. The alternator is the main part of the charging system. It doesn’t need maintenance and needs to be replaced when it is stopped with other problems.  

How Long Does a Battery Lasting With a Bad Alternator?

Many factors are affecting how long a battery will last when the alternator isn’t charging it. The type of engine, how modern the car is, and the number of electronic systems.

The average car battery life is somewhere between two to five years. However, for many cars, especially older ones, the battery life can be reduced by up to 10 percent, easily be resolved by replacing the battery.

Why Is an Alternator Going to be Bad?

The alternator is a relatively simple device that powers your car’s electrical system, and it’s not hard to see how it can fail. Just like any other type of mechanical device.

If your car is having issues, you will have to have the alternator checked. It is the most common problem with cars. It is also fairly easy to fix. The most common reasons for a damaged alternator are-

  • Overheated an alternator belt ruined its bearings,
  •  it can be damaged by dirt, dust, and other debris.

Are There Any Risks Associated With Running a Car Without Replacing the Battery Along With the Alternator

Running a car without replacing the battery along with the alternator can lead to a number of risks. The alternator is responsible for recharging the battery while the car is running, so if the alternator is not working properly, the battery will not be charged and the car may stall or not start at all. Additionally, if the battery is very old or in poor condition, it may not be able to hold a charge even if the alternator is working properly. This can lead to frequent breakdowns and a shorter lifespan for the battery.

Another risk is that the alternator may not be able to provide enough power to the car’s electrical systems, which can cause issues with the car’s lights, radio, and other accessories.

It is recommended to replace both the battery and alternator at the same time to avoid these risks and ensure the car’s electrical system runs smoothly.


Do you have to replace the battery when replacing the alternator? By this question, we may know about a bad alternator. A weak or bad alternator, also known as an undercharged or flooded alternator, is the most common failure on all new vehicles. The loss of charging power that this causes is generally not noticeable, but the result is that the battery will quickly start to lose its ability to hold a charge. If this happens, you will notice that your car starts to run very hotly, the lights fail, and the car dies.

You can still use your old battery if it is less than 8 years old and has been properly maintained. However, it is advisable to replace your battery when your alternator is replaced because an older battery may not keep up with the electrical demands of a newer car.

So, If you are looking to replace the alternator, it isn’t compulsory to replace the battery. If you have an old battery, you may want to replace it.

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About This Writer

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Hi, I am responsible for the 'Homeowners Power Solutions' category. My name is Liam Jaxon and a licensed technician with 7 years of experience in vehicle batteries, electrical gadgets, and home appliances. My working experience in different residential & light commercial electrical sectors and the automobile industry helped to acquire vast knowledge in this industry.

Hi, I am responsible for the 'Homeowners Power Solutions' category. My name is Liam Jaxon and a licensed technician with 7 years of experience in vehicle batteries, electrical gadgets, and home appliances. My working experience in different residential & light commercial electrical sectors and the automobile industry helped to acquire vast knowledge in this industry.

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