Eight Things that Can Deplete Your Car Battery. How To Avoid It

It’s everyone’s worst nightmare – you head out to work in the morning and the car won’t start. The dead battery has you wondering what happened and how it could have been avoided. 

Here are 8 possible causes of car battery drain. Some might surprise you. The team will also examine ways to identify the cause and what to do to stop it happening again. Let’s begin with the most common reasons:

A parasitic drain is the most frequent reason why a car's battery drains. This is caused by an electric consumer that is not working properly, such as a door lock or trunk lock switch. Broken alternators or human mistakes, such as forgetting electricity consumers, can cause this problem.

All of these problems can lead to your car's battery dying, leaving you without an alternative transportation option. Here’s a more detailed list of the possible things that could drain your car battery:

Eight Reasons Your Car Battery is Drained

1. Human Error

We’ve all been there. At the end of an exhausting day you pull into the driveway. You don't turn the headlights on and then head in the opposite direction. Another possibility is that you have not closed the trunk or door properly.

These lights can be used overnight but your car's battery will eventually die without any way to charge it. That’s why the car won’t turn over in the morning. 

Many cars with modern technology have an alert system that will remind you when the lights turn on and when the door opens. If you don’t have one of these, it’s important to remain vigilant against these common errors.

2. Poor Charging

If the charging system is not working, your battery can drain, even as you drive. The battery will be charged during your trip if everything works as it should. 

However, any loose belt to the alternator or worn-out tensioner can cause the system to stop charging, and you wouldn’t even know it’s occurring. 

RELATED: 6 Reasons Why an Alternator Isn't Charging

3. Parasitic Drain

Parasitic drain is when the vehicle's power source continues to work even after you turn it off. Some parts, like radio presets and memory, use battery power constantly. 

The parasitic drain can occur when there is an electrical problem. This can be caused by defective wiring or faulty fuses. This is the list of most common parasitic drains that can cause a dead car battery.

1. Failure Door Light Switch
2. Faulty Door lock actuator with integrated light switch
3. Lock switch for trunk
4. A bad car stereo, or its wiring.
5. Installing any after-market parts incorrectly.

You could have many other causes. These are just a few of the causes. The most likely reason is a defective door switch that allows the lights to stay on, draining the battery.

4. Extreme Temperatures

Your car battery doesn’t handle extremes well. The battery may fail if the temperature drops below 10° Fahrenheit and exceeds 100° Fahrenheit. 

Crystals of lead sulfate begin to form, leading to long-term depletion. This makes it harder to fully charge your battery. 

5. Broken Alternator

The alternator charges the battery. The alternator also powers the electric systems of the vehicle. 

The battery will not recharge if the alternator fails. A typical alternator lasts between 100,000- 150,000 miles. 

Related: 6 Signs You Have a Bad Alternator

6. Connectors to loose or damaged batteries

It can prove difficult to charge your battery fully even if it is operating correctly. 

It doesn’t hurt to do a regular inspection of the cables and terminals to ensure everything is clean and connected. 

7. Driving Short Distances

To charge your battery, the alternator will need to be charged for a while. If you only drive down the street to visit the local grocery store, you aren’t allowing the alternator to work.

It is best to go on longer trips, and preferably along the highway to get a fully charged car. 

8. Old Car Battery

Sometimes the battery becomes too old or weak to charge. Normal conditions will allow the battery to last for between 3 and 5 years. 

If you are a driver who drives in extremely cold temperatures, or pushes your vehicle beyond its capabilities, then you may need more batteries. 

Diagnostics for a dead car battery

So, what’s causing your battery to drain and how can you fix it? It is easy to identify the cause if something was left running because you did not make a proper inspection. You can check for loose connections or corrosion by doing a quick inspection. 

But it is possible to locate a parasitic source. These steps will help you find the problem.

1. A Multimeter can be connected
2. Make sure to check the fuses
3. Fix the problem

A Multimeter can be connected

Make sure to turn off any devices and have your battery fully charged. Turn your multimeter on the highest setting to charge the battery.

A parasitic draw is when the battery's reading exceeds 50 milliamps. You should see between 20-50 milliamps on your clock or other devices that use the battery.

Make sure to check the fuses

While you monitor the multimeter, pull out one fuse at time. You can start at the lowest amp and work your way up.

You can identify the problem by pulling out the fuse that is causing the readings to fall significantly. Consult the fuse chart in your owner’s manual to determine what component is causing your problems. 

There will be more investigation required. Let’s say the fuse runs your audio system; you still have to figure out if the radio, power antenna or other device is drawing power. 

This will cause the fuse to stop working. That’s your offending component. 

Fix the problem

Once you know what part is draining the battery, it’s time for a replacement. While some parts are simple to fix, others may require assistance from a technician. 

After you have replaced the part defective, repeat the multimeter test to confirm that the draw is stopped. 

How to prevent a car battery drain

Car battery maintenance is essential to ensure your car's readiness for use. These simple tips can help prevent your battery from draining. 

• Regularly clean out any dirt or debris. Don’t let the top of the battery get dirty or corroded.
• Secure connections can be made by checking the battery terminals and cables frequently.
• Don’t use electrical devices when the engine isn’t running. You can turn on your car to control the radio and other accessories. 
• Securely clamp down your car's battery. Shorter battery life may be caused by vibrations. 
• Place your vehicle in a garage away from any elements.
• When it gets cold, use a blanket made of battery. 
• Take longer drives.

With a few maintenance steps, you won’t have to be late for work again.