Can A Bad Alternator Ruin A Battery? – A Detailed Answer

Both alternator and electric battery play an essential role in vehicle technology. These two work together to keep your car running smoothly.

That’s why you might ponder, “Can a bad alternator ruin a battery?”. Does it lead to the failure of the other device while one device is damaged?

This blog will provide you with some in-depth information to answer the problem between these pieces of electrical equipment.

Can A Bad Alternator Ruin A Battery?

Can A Bad Alternator Ruin A Battery

The alternator is one of the core details of machines. It is a generator of electric power that gives extra power (physics) when the car’s running.

As it charges the battery, we notice that it has a significant influence on an automotive battery.

Can the alternator kill the battery? Yes, it can. Although it cannot always harm the new one, sometimes we can meet situations that affect the source.

Because of these above effects, many people wonder if they should replace both a new battery and alternator to confirm the problems can not happen.

How To Determine If Battery Or Alternator Is Bad?

How to tell if car battery or alternator is bad? In automotive technologies, we have many questions like that. We can answer by focusing on their signs.

In case of battery or alternator bad, there are some symptoms you should pay attention to.

Bad Battery

When your car doesn’t start, the initial reason we think is the source of electricity. Yet, you have to check if it is the cause of the problem. There are some signs you must notice:

Bad Battery
Bad Battery
  • This component will work well for 3 to 5 years. Thus, the older they are, the lower their ability to charge. Although we can use a rechargeable battery to replace the bad ones, the older ones contain more corrosion from leaks.
  • The swelling often occurs at excessive temperatures as inner fluids and components extend. It may be swollen or deformed.
  • Your car needs longer to start up than normal, indicating that the source is low on charge. It could be flat if you hear a “click” when you turn the ignition key.
  • You turn on the ignition system and then switch on the headlight. When this equipment is weak, it will turn to dim headlights or dashboard lights. It won’t light anything in case the component is entirely dead.

Bad Alternator

This can be the culprit when you don’t face these above issues. You can notice signs when your car has problems:

Bad Alternator
Bad Alternator
  • The belt is under constant tension and friction. It can produce a burning smell as it wears down because it’s near the hot engine.
  • Your automobile’s engine stalls instantly after starting the car.
  • Your headlamp darkens or lights unevenly and possibly flickers. That means the vehicle’s alternator has a problem providing constant power.

How To Test If The Battery Or Alternator Is Bad?

Because of these problems, we have to conduct a bad battery or alternator test. Let’s take a look at the cell first. Taking advantage of electrical engineering, we will instruct you step by step:

  • Step 1: We proceed to check your terminals for corrosion signs based on electromagnetism. Release the clamp from the negative, then the positive clamp to clean the corrosion. You might use wire brushes and cleaners to clean.
  • Step 2: Review the wiring: Check the wire of the terminal clamps to ensure no damage or corrosion. Replace with zinc terminals if the terminal clamps are heavy corrosion.
  • Step 3: Voltage check: Connect your multimeters to the negative terminal and the positive terminal. A voltage is lower than 12.6V will determine the battery is weak, and you need to replace it.
Battery Test
Battery Test
  • Step 4: Start engine: Link multimeters to the positive and negative terminals. Find someone to help you run the engine while looking at the multimeter. When the voltage decreases below 12V, you need to replace it.

How about automotive? How to test alternator if car won’t start? Luckily, we have a short test without entry to the multimeter.

  • Step 1: Find a dark or dim place: You should park your car in the dim light area to take a test. You can choose the street without street lights.
  • Step 2: Switch on the headlamp: Turn on the key in the ignition to start the machine. Please switch on your headlamp to the standard setting.
  • Step 3: Turn on accessories: You can turn on the stereo, air conditioning, and heated seats as long as your car has.
  • Step 4: Scan the headlamp: Concentrate on the luminosity of your headlamp when you turn on the accessory. In case the headlights begin to dim significantly, this equipment is worse than normal.


What Are Some Problems About Alternators?

Several questions: “Can a bad alternator destroy a new battery?” “Can an alternator kill a battery?” “Will a bad alternator kill a battery?” “Can a bad alternator kill a new battery?” “Can a bad battery ruin an alternator?” I will answer “Yes” for all of them.

A bad alternator can directly affect the battery, which leads to damage to the electrical components and the car as a whole.

This failure also brings economic trouble. Indeed, the money to own these pieces of equipment is costly. Not to mention the quantity of money that we must spend maintaining and repairing the equipment if there is damage.

Driving a vehicle with a bad component can put the driver’s life in danger. Even if the person has activated it correctly and safely, there is no lifetime guarantee.

What Are Solutions To Alternator Or Battery Issues?

You have to spend from $200 to $800 depending on the car. Yet, it will be worth changing. Though the new ones can be expensive, they will prevent damage to your car.

You can come to the local auto shop to find suitable gear and replace the old one at home.

Another way we recommend is you should ask a professional (can be mechanical engineering) to find out battery vs alternator problems. They will advise and give helpful guidance for your car, and of course, they will also help you choose the best artificial objects.

How Long Will A New Battery Last If The Alternator Is Bad?

For those who own motor vehicles, they might know that the battery can continue working despite the bad alternator. So, you have a chance to get back home before it is low.

With a new and fully-charged battery, the time you have is only 30 minutes. However, if you’re lucky, you will have two hours to take a drive.


After reading this blog, you could self-answer: “can a bad alternator ruin a battery?“. You can also quickly realize how car battery or alternator bad is.

Hopefully, our guidance can allow diagnosing battery or alternator state at home. When you have a more complicated matter, you should take your car to the repair shop and change new manufactured goods.

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