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can a bad alternator ruin a new battery

Can A Bad Alternator Ruin A New Battery?

The alternator is in charge of charging the battery while your car is running. So, these two components rely on each other to work. But can a bad alternator ruin a new battery?

The short answer is yes. When the alternator breaks down, the battery can’t receive enough electricity to power the engine. Your car will then experience multiple issues. 

If you don’t often pay attention to the alternator, start to form that habit today. We will help you picture how vital this component is. Let’s see!

can a bad alternator ruin a new battery

Can A Bad Alternator Ruin A New Battery?

Yes. A bad alternator may ruin the new battery. There are various reasons why the malfunctioning alternator causes the battery to die. 

The alternator is a critical component of machines. As an electric power generator, it provides additional power when your car is running. 

The alternator affects how the car battery works. Hence, even when you have just installed the battery, a bad alternator may cause it to die.

The reasons for the bad alternator draining a new battery include the following:


A good alternator charges the battery with the proper voltage level recommended by the manufacturer. However, if it produces too much voltage, it will overcharge the battery. 

Overcharging causes damage to the battery plates and cells. It will finally break down, affecting other components in your vehicle. In some cases, the faulty battery will cause the starter to burn out.

Irregular charging 

The car battery requires a consistent charge to work effectively. However, a bad alternator may result in an irregular charge. It will cause the battery to experience continuous cycles of undercharging and overcharging, shortening its life considerably.  

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Lack of charge

When an alternator fails, the generated electricity can’t power the battery. In this case, the power supply is insufficient, inconsistent, and inadequate. 

As a result, the alternator fails to fulfill the battery’s requirements. The lack of charge will ruin the battery in the end. 

Ripple Voltage

Ripple voltage is another issue caused by a faulty alternator. It’s when the alternating currents travel through the rectifier of the alternator.

The ripple voltage can also ruin the whole electrical system of your car, which may be dangerous.

How To Check If Alternator Or Battery Is Bad

How To Check If Alternator Or Battery Is Bad?

A bad alternator can ruin a new battery. However, you can’t blame the faulty alternator for the battery issues at all times. So how to determine the exact cause?

Step 1: Check For The Signs

A bad battery and alternator can cause your car to stop. If the alternator is bad, you will notice these signs:

  • The belt is always tense and abrasive. Because it is so close to the hot engine, it might create a burning odor as it deteriorates.
  • After starting the vehicle, the engine immediately stalls.
  • Your headlight lights unevenly and may flicker. It indicates the alternator is having trouble delivering steady power.
  • Some signs of bad alternator sound are the whining and growling noises from under the hood.

On the other hand, a car battery can last for three to five years. However, with improper charging cycles, it will break down soon. Here are some signs to determine that you have a bad battery:

  • The battery swells when inner components and fluids expand at high temperatures. 
  • Your vehicle takes longer to start than usual, signaling that the power source is too low. It might be flat if you notice a clicking sound when you press the ignition key.

Step 2: Perform Some Tests 

The signs above make you suspect the issues in the bad alternator vs bad battery. However, you need to perform some tests to confirm. 

With The Multimeter

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Check the cells in the battery first. A multimeter can help you test the electrical engineering by following these steps:

  • Check for any sign of corrosion and damage in the wire of the clamps. If they have worn out, replace them with zinc materials. 
  • Attach the multimeters to the positive and negative terminals. If the reading is lower than 12.6V, you have a weak battery that requires a replacement. 
  • Alternatively, you can perform a start engine check. Ask your friend to run the engine. Then, check the multimeter to see if the voltage drops below 12V. If yes, replace the battery. 

Without The Multimeter

If you don’t have a multimeter, please take these steps to test if the alternator or battery is bad. This test focuses on the alternator: 

  • Park your vehicle in a darkly lit location to conduct the test. A street without lights is a good idea. 
  • Start the engine by turning on the ignition key. 
  • Switch on the headlamp to its standard mode. 
  • Turn on the radio, heated seats, and AC. 
  • Check the luminosity of the headlamp when you switch on the accessory. If the light dims, the alternator may be worse than expected. And the cause for the reduced engine performance is the alternator, not the battery. 

How Long Will A New Battery Last With A Bad Alternator?

If your battery is still good and fully charged, you can keep driving with a bad alternator for about 30 minutes or 20 miles. But if the battery is low, consider towing your car

A bad alternator will result in many problems. For example, you can’t start your car, or the electronic functions become unusable. 

Even though your car can still work with a bad alternator, it still needs repair. Once the alternator fails, the battery will suffer multiple issues that directly affect the engine. 

What Causes An Alternator To Stop Working? 

The bad alternator will ruin your battery even when it’s still new. So what can damage an alternator?

Wiring Problems

The alternator receives power from many wires in your car. If one of them breaks down or wears out over time, the alternator will fail to deliver the power needed for the battery. 

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Computer Problem

Computer systems, like the ECU, are integrated into modern cars. These systems control almost every part of the car, and the alternator is one of them. 

As a result, even if the alternator is in good working order, a fault or error in the computer system might prevent it from charging efficiently.

Bad Fuse

Fuses keep your alternator functional. Unfortunately, a power surge will blow out the fuses. The alternator will then malfunction. 

Broken Belt And Pulley

The alternator uses the mechanical power from the pulley and belt to produce the electrical energy for your car. However, these parts are not durable and may break down easily.

While the pulley can last longer, the belt is flimsier and can crack eventually. If one of them fails, there won’t be enough mechanical power for the alternator to use. 


The alternator emits heat while working. However, you will get a damaged alternator if it gets too hot. 

Wear And Tear

Every component in your car may wear out over time, and the alternator is no exception. The bearing, brushes, and some parts will deteriorate, causing the alternator to stop working.

How To Keep Driving With The Bad Alternator?

If you can’t fix the lousy alternator immediately, use these tips to keep driving until you see the nearest garage:

  • Use a jump-start booster to get the most power when starting the engine. 
  • While driving, try to preserve power by avoiding using equipment such as headlights, stereos, and fans. 
  • As you travel at high speeds, you may go further in less time. Yet, keep the speed within the legal limit at all times.
  • Check the battery’s voltage with a voltmeter.


Can a bad alternator ruin a new battery? Yes. Since this component delivers power to the battery, it will cause charging issues when damaged. As a result, the battery can’t power your engine without the required electricity. 

However, the faulty alternator is not the only cause of a failed battery. You should, therefore, check both components to determine the root of the problem and solve it. 

Thank you for reading! 

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