Can A Bad Alternator Ruin A Battery – (Ultimate Guide)

At times you might end up experiencing problems when starting your car. Even though it is common and mainly claimed that the issue originates because of a dead battery, this can not always be the root cause, and there can be trouble with the alternator. Let’s investigate can a bad alternator ruin a battery.  

The role of an alternator is fundamental for the car to function properly. The car’s engine is responsible for producing mechanical energy but has to be converted into electricity before being utilized by the vehicle. 

A car’s charging system contains a battery, voltage regulator, and an alternator that converts the provided mechanical energy to produce electricity through an alternating current. Generated alternating current is then transformed into direct current and sent to the battery to be used for charging. 

Can a bad alternator ruin a battery?

Now that you know that an alternator in the vehicle employs the task of ensuring to charge the battery, there is a high possibility for it to either over or under-charge the battery. So can a bad alternator ruin a battery?

bad alternator
bad alternator

The answer to this question is that yes, a bad alternator can ruin a battery, mainly when the battery installed in the car is new. There are numerous reasons for which a faulty alternator can result in a dead battery, and in turn, we will be examining them all. 

Overcharging the battery 

If your car has a lousy alternator, you must know that it can make a bad alternator ruin a battery. This will signify that the alternator will not be consistent in how direct the current is delivered to the battery. Due to the troubles within the alternator, it cannot manage and regulate the charges of the volt sent to the battery.

Consequently, the alternator will send a surge of current with a high charge to the battery resulting in the device overcharging and the premature failure of the cells. Beware of a bad alternator because an overcharged battery can harm various essential components of your car. 

Irregular charging 

Batteries in a car are not the primary power source for your vehicle but contribute the most to its functioning. The alternator is responsible for ensuring a stable power supply to the car while running, so can a bad alternator ruin a battery?  

Therefore, a bad alternator can cause irregular running of the car, which would have to switch to the substitute power source- battery. When the battery will also not be fully charged or, for a matter of fact, overcharged and sourcing the car, the electronic device will dwindle. As a result, a bad alternator can ruin a battery and damage your vehicle’s engine.

Lack of charge 

When an alternator goes faulty, as an outcome, it stops redirecting the produced power towards the battery. So this is when you encounter complications while starting your car. 

The insufficient supply of power by the alternator in the form of alternating current is not only inconsistent but also an inadequate amount which is not fulfilling for the battery to serve its purpose. 

Thus, a lack of charge from the alternator can ruin your car’s battery.

Symptoms of a ruined battery 

Trying to determine if your battery has been completely ruined because of a bad alternator in the car? Then look for the following signs. 

Dim dashboard lights 

If the lights in the dashboard are dimming unnecessarily and frequently, the cause indicates that the battery has been ruined. Start by checking the gauge of the battery. Usually, the battery is supposed to give off a charge even when the vehicle is not running. 

However, if not, you must watch out because the battery is dead or either will be soon enough. To further confirm your suspicion, see if the windshield wipers, automatic windows, and lights are working. Well, if they are not, you have your answer right there!  

Radio not working 

Again the battery of your car is responsible for the radio to run, and if you experience an issue with the radio, such terms as if it keeps stuttering or turning off. This sign is a clear indication that the battery is not well charged.

Before concluding that your car’s battery is ruined, charge it thoroughly and then try again. However, if the radio still glitches, it implies a ruined battery

The car starts and turns off immediately. 

Even though a car’s engine starting and immediately turning off can happen for various reasons, one of them being can a bad alternator ruin a battery. But most of the time, the primary cause is a ruined battery. When experiencing this issue at the first instance, check the battery as it can occur because of the battery having a low voltage, insufficient to power the ignition of your vehicle’s engine

Frequently Asked Questions

How long can a battery last with a bad alternator?

There is no specific time limit for your car’s battery to last with a bad alternator, but after the vehicle runs for approximately 25-30 miles. If the battery is charged, it will power your car; if not, the vehicle will immediately stop. 

What is the reason for an alternator to drain the car’s battery? 

An alternator can cause the car’s battery to drain because it has a defective or corroded diode, causing faults in the circuit which delivers direct current to the battery. 

What causes an alternator to go bad? 

An alternator goes bad for various reasons, including the car constantly running without a break in it, extreme temperatures for the alternator, and dirt build-ups on the device. 


In this article, we have provided you with an answer to resolve the long-standing confusion with can a bad alternator ruin a battery. Additionally, we have added symptoms that can help our readers identify the exact incident indicating that the battery has been ruined.

We advise you to always look out for your car’s battery and to charge it properly to avoid being involved in life-threatening accidents.

Please Share This Post:

Hi! My name is Tom Watson Founder of Garage Fortress. I am happy to say that I am the owner of Garage Fortress which is a website focused on automotive technology and cars. I studied technology for 15 years at a university and got an Advanced Technical Certificate in Automotive Technology.

Leave a Comment