Why Does My Car Battery Keep Dying? 6 Main Reasons & Expert’s Guide

4.6/5 - (9 votes)

While driving, you will inevitably encounter unfortunate situations such as dead batteries, and they even endanger you and others.

When it is discovered that your car battery is dead, the cause can come from many different sources, especially if this situation occurs continuously for a short time. So, why does my car battery keep dying?

This article covers the symptoms, causes, and different ways to fix it.

Why Does My Car Battery Keep Dying?

Car users will face a deadly storm and some common reasons, such as a loose battery connection, even if the storm is corroded.

In addition, your device may also drain continuously or have problems with its charging, especially in inclement weather.

You should look into and consider a potential problem going on within your product and find a way to fix it quickly.

Headlights left on

Some people often forget to turn off the headlights or dome lights, making the lights dim. Therefore, they will drain the battery overnight.

When you are on the road or need to go out at night, you should check your lights to ensure they are still working properly.

Manufacturers can create models with headlights that work continuously. However, it can not work forever when you have a problem with your system.

Weak battery

Weak batteries

Weak batteries

If you have an old or poorly maintained version, it is usually weaker and does not charge well.

Assuming your car is in a suboptimal state and drains quickly or doesn’t have enough power to run the car, the storm is dead and needs to be replaced.

Most manufacturers advise you to replace the battery every 4-5 years. However, the exact number will depend on many different factors.

Corroded connection

Electrode corrosion occurs when the potential difference between positive and negative ions is aggravated.

At that time, the anode will erode, and the battery charging becomes ineffective.

In most cases, you will almost have to replace a new one to ensure maximum performance. Corrosion or losing battery connection wires can also cause weak or dead batteries. It will prevent the charging system from disconnecting the batteries while driving.

Hot temperatures

Hot car engine

Hot car engine

Hot or cold weather won’t kill new batteries, but low or old batteries can fail. Whether that is too hot or too cold can also increase other underlying problems.

In general, any device in an extremely hot or low-temperature environment can damage or weaken the batteries a lot. Specifically, if you put your product under extreme heat and cold, it tends to cause the formation of sulfate crystals.

These substances will be harmful and devastating to the system. In the long run, your device will bend and lose its original appearance if it is high. Conversely, low ambient temperatures can reduce the battery’s power delivery.

To maintain a stable temperature, you should leave your car in the shade during the hot summer or keep the engine running regularly in winter.

Charging problem

Charging problem

Charging problem

The task of the charging system is to provide power and connect the batteries to work properly. Therefore, when the belt and tensioner are worn, it may reduce the charging speed or cause problems.

Short Trips

Car short trips

Car short trips

People who regularly take short trips may face short-term engine shutdowns.

Therefore, it will not be enough for the batteries to regain lost energy, which can reduce the car battery’s life. You need to take at least one long trip in half a month to completely recharge.

While the battery has turned on the motor, the unit will resume steadily as the alternator recharges.

How To Fix

Complete guide to fix

Complete guide to fix

Below, I give some of the most effective ways to deal with the above causes respectively. Please read carefully and follow along; it can help you a lot!

Lights Checking

The job of a car version is to provide power for headlights, dome lights, and many other accessories under all circumstances, even when the engine is off.

However, this ability is also somewhat limited. It shows that when the engine stops running, and something still works, the batteries will almost certainly die.

Specifically, when you leave the headlights on, your battery will be weakened while doing the job quickly. In addition, when you leave the small dome light on overnight, the device’s batteries will also quickly drain.

The best solution for you is to test your product at night when it is dark, and the dome light is dim because it will make it easier for you to see the device.

The market offers cars that turn on the headlights, dome lights, or radio when you turn off the engine and remove the key.

It will probably turn off on a timer after some time, but if everything stays the same, you already know why the battery is draining so quickly.

The maintenance

Sometimes the signs are not as obvious as some of the problems we mentioned above. At this point, you should take your device in for basic or intensive maintenance if necessary.

Those manufacturers often seal their batteries. However, if it does not close, you need to ensure that your products are properly filled with electrolytes.

One possible problem is that the electrolyte level has dropped below the top of the lead plates.

In many cases, you can completely rinse the cells with a faucet but ensure their quality. The best advice for you is to use distilled water. Besides, you can also use the hydrometer to check your batteries.

It is a device that looks at the specific gravity of the electrolyte in each cell and helps you know when the battery needs to be replaceable.

The load tester is also another tool for testing, but it is expensive. The principle of operation of this device is to put a load on the battery to simulate the starter motor. It helps you to check the battery voltage charged and unloaded.

The most important note is that you should be concerned about the short-circuited battery that can explode, and you need to have experience and careful protection before doing it.

Corrosion Remove

You can completely remove this problem with baking soda, water, and a stiff bristle brush. However, you need not put baking soda inside the battery.

Also, leaving a mixture of baking soda and abrasives on the surface of your driveway or garage floor will cause stains that are hard to deal with.

Another method you can use is sandpaper or a specially designed tool in the form of a wire brush. It helps you create bright and clean equipment and has a much better electrical connection.

A little trick is that you can take advantage of kerosene to do this operation in a much more standard and simple way.

Of course, you should only use the smallest amount possible to make the process faster.

Parasitic Drain Checking

You can check the current on your device by disconnecting the battery cable and testing the current. You should use a multimeter with the highest amperage possible in many cases.

Besides, you can also use the inspection light to look at the drainpipe, but its accuracy is lower. You also disconnect the negative battery cable and complete a circuit between the battery negative terminal and the ground.

However, it will be difficult for this device to know the amount of current dissipation just from the lamp’s brightness.

The trunk, glove compartment, and other lights that come on due to malfunction are also likely to drain the battery overnight.

The best way to track is to do a process of removing a multimeter or test light connecting and removing the individual fuses until the drain goes away.

Next step, you will identify the corresponding circuit to know the exact problem.



In this section, I have gathered accurate answers to some of the most frequently asked questions on motor and car forums. Do not skip any question because it will most likely be useful to you in certain cases.

1. How do I know my alternator is bad?

Identifying a broken generator is not a difficult job or requires a high level of expertise. You can detect the problem yourself through some signs:

  • Dim or too-bright lights

Dim or too bright lights are the most common sign when a generator starts to fail. The cause is that it does not provide enough voltage for the device to work. Sometimes the lights may blink or go from dim to bright or vice versa.

  • Dead battery

Noticing a dead battery can also signify that your alternator is malfunctioning. When the device does not work well, it will not provide enough battery for the engine to operate, and the battery will quickly run out.

  • Accessory error

Accessories that are slow or not working can be caused by the generator not providing enough power. Therefore, when you keep the window up for longer than normal time, you may experience generator problems.

  • Trouble starting

When the generator does not fully charge the battery, it will cause you to have trouble starting.

Specifically, when you turn the key in the ignition, you only hear the click instead of the engine hum. Even your car is stalled because the spark plugs do not receive enough electricity.

In addition, you may also see other signs such as growing or whining noises, the smell of burning rubber or wires, and a warning light on the dash.

2. How much does an alternator cost?

With a minimal budget, you can own a product that fits several car models for around $180. Besides, if you are the owner of a high-end car or a supercar, the price of an alternator can go up to more than $1,000.

Overall, for a stable device that works well, you need to spend about $500.

There are now many brands that can supply alternators. Therefore, their designs, quality, and lifespan are also very diverse.

3. What causes an alternator to fail?

In general, replacement generators fail because of their lifespan or use. Besides, you can also consider other reasons why the generator fails prematurely.

Specifically, in some cases, the cause comes from a liquid leak in the car’s equipment leading to damage.

It’s quite common that engine or power steering fluid has spilled or entered the generator. It causes the device to be inoperable or misbehaving.

4. Can you test an alternator out of the car?

You can completely perform the alternator test from the car. Specifically, your job will be to check the battery’s voltage when touching the prongs of the multimeter. This device will be placed at the poles after the vehicle is off.

Next, you need to note the number on the clock. The standard value of the voltage is usually in the range of 12 to 13 volts.

Finally, you need to start the car and check the voltage value in the battery while the car is running.


The truth is that all batteries die over time, but you should use and maintain them to keep them working and holding well. For any reason, when the battery is dying, it will greatly reduce the life of the device.

In the article, we have provided some reasons why the battery is constantly dying and how you can prevent this situation. You can prevent corrosion, make sure the battery is connected, and don’t let the electrolyte fall out.

This task is not that simple if you are a beginner. Besides, if you have a problem and really can’t diagnose or solve it on your own, try to consult a professional for the best solution.

Hopefully, the information in this article is useful to you.

Thank you for reading!

Frank Galvin

Hi everybody! My name is Galvin, an automotive engineer and team leader of Autopartguide. I have a passion and a special love for cars and all auto parts related to them. You can see I'm excited all day with my cars.