7 Things That Drain Your Car Battery

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Your car battery is one of the most important parts of your car. If you’re car battery dies or is draining you will start to experience a variety of issues. 

Unfortunately, it’s overwhelming to determine what is draining your car battery. 

Don’t worry. In this post, I will go over 7 things that can drain your battery, symptoms of a draining battery and how to test your battery. 

After reading this you’ll have everything you need to make sure your battery is in tip top shape. 

Let’s get started. 

1. Leaving The Lights On In Your Car

We’re not perfect. Whether you’re in a rush or tired after a long day of work, we sometimes forget things. 

Unfortunately, if you leave the lights on inside your car, it can cause your battery to die. 

The two main things you forget to do that will cause your car battery to die are: 

  1. Leaving your headlights on 
  2. Leaving your interior lights on 

Leaving your headlights or interior lights of your car on will keep the battery running. Depending on how long you leave these on, it can drain your entire battery. 

If you leave these lights on for less than three hours, your car will typically start without an issue. But in most cases, if you leave your headlights or interior lights on for more than eight hours, it will drain your battery. 

If you have a brand new battery, it might be able to keep its charge even if you leave your lights on for longer than 8 hours. As batteries begin to age, they will start dying faster. 

While some vehicles have alarms or automatic turn-off features this is not always the case. Don’t worry, if your vehicle doesn’t have this feature you can install and alarm yourself. 

This is a great way to never leave your lights on even if you have an older car or a car without a reminder alarm. 

2. Parasitic drain

Parasitic drain is when the car’s electrical components continue to drain the battery even after the engine is off.

In most cars, a certain amount of parasitic drain is normal.

Parasitic durian becomes an issue when there are electrical mishaps. This can cause an excess of parasitic drain that causes your battery to die completely.

Parasitic drain also becomes an issue with older batteries.

As batteries get older, they become less effective at dealing with parasitic drain.

This is especially an issue if the parasitic drain in your car is higher than normal.

Newer cars typically have more parasitic drain than older cars because they have more electrical components.

You can expect between 85 and 50 milliamps of parasitic drain in a newer car.

On the other hand, older cars typically have less parasitic drain since there are fewer electrical components. You can expect less than 50 milliamps of parasitic drain in an older car.

Fortunately, testing your car’s amount of parasitic drain can be done easily with a multi-meter.

Unfortunately, determining the specific cause of parasitic drain is not easy and typically requires professional knowledge or advanced software.

3. Defective alternator

The alternator recharges your vehicle’s battery while you are driving. 

If your alternator starts failing, it will stop recharging your battery. 

You might not notice this issue immediately. But, over time, as you continue driving, your car battery will continue to drain. 

Eventually, your car will not turn on, or your vehicle’s electrical components will turn off once your battery dies. 

Other causes could also be:

  • Computer issues
  • Wiring issues
  • Bad fuse
  • Broken pulley or belt

The great thing is that you can easily test your alternator with a multi-meter. Typically, a good alternator will have a reading of at least 13 volts. 

An alternator with a perfect reading should have a reading between 13.5 and 14.5 volts. If your alternator is reading above 15 volts, its likely faulty and also needs to be replaced. 

If your alternator is below 13 or higher than 15, this is likely why your battery is draining. 

Check out the video below for instructions on how to check your alternator. 

4. Extreme temperature

Extreme temperatures are never good for your car battery. Both high and low temperatures can hinder your car’s ability to hold a charge.

Extreme Cold

Most people know that batteries don’t perform as well in cold weather. The same applies to car batteries.

At freezing temperatures, 32°F, your car’s battery will experience a 35% loss in charge. As the temperature continues dropping, your car will continue to lose charge. Older batteries will lose more charge at lower temperatures.

In some cases, an old battery that is low on charge freeze at -10°F while fully charged batteries can withstand temperatures as low as -80°F.

Extreme Heat

Extreme heat can also have an impact on your car battery. While extreme cold will drain your battery, extreme heat will destroy your battery can reduce the charge.

It’s typically expected for high heat to reduce the lifespan of your car battery. For example, the hotter temperatures of states such as Arizona, Nevada, and California typically result in shorter lifespans for car batteries.

Typically when the temperature outdoors reaches 92°F, your car will begin to lose some charge. The expected level of charge will vary depending on the type of battery.

When exposed to extreme temperatures for prolonged periods, it can cut the lifespan of your battery in half.

Prolonged exposure can also evaporate the electrolytes inside your battery and reduce the charge level and make it harder to reach full charge.

You can purchase batteries that are designed to handle hotter temperatures.

These batteries contain additional electrolytes allowing them to handle prolonged exposure more effectively. They also typically allow you to refill the electrolyte once they begin to evaporate.

5. Excessive short drives

Excessive amounts of short drives can drain your battery.

The main reason for this is that your battery uses the most energy to start your vehicle. When you turn off and start your car many times in a short period, you drain the battery without allowing your alternator enough time to recharge it.

Another reason that short drives can drain your battery is that alternators provide their maximum output at around 6,000 RPM.

This typically means that your engine needs to be anywhere between and 2,500 to 3,500 RPM. Depending on your car, the speed to reach this RPM may vary.

You can check out the video below to learn how to determine your engine’s RPM while you drive.

You typically need to drive between 30 minutes and 1 hour at your alternator’s maximum output to charge your battery fully.

If you’re driving many short trips, you don’t allow your alternator to operate at its full capacity. Over time your car battery will continue to drain and eventually die.

6. Corroded or loose battery cables

An often-overlooked reason that your battery is draining is corroded or lose battery cables. 

Corrosion can cause your battery to more power than it’s using. The same can happen if there is corrosion on the terminals. 

It’s essential to inspect the battery for corrosion regularly. If you see corrosion beginning to build up, you should clean your battery or replace your cables. 

Cleaning corrosion on cables or your battery is much easier than it sounds. A tough bristle brush or toothbrush, water, and baking soda are all you need. 

Possible causes of corrosion could be:

  • Electrolyte leakage
  • Overcharging
  • Chemical reactions
  • Overfilling with water
  • Hydrogen reacting to other gases
  • Battery aging

7. Old battery

Old batteries are another common reasons your battery is draining. Car batteries don’t last a lifetime. 

It’s typically recommended that you replace your car battery every 4-5 years. In some cases, you might need to replace your battery more often. 

Some situations that might require you to replace your battery more often include: 

  • Poor maintenance 
  • Electrical issues in the past 
  • Corrosion 
  • High or low temperatures 
  • High mileage driving 
  • Advanced or enhanced electrical systems

To avoid replacing your car battery this often, I recommend investing in a higher quality battery to start.

These batteries can typically handle harsher conditions better and are designed to have longer lifespans. 

Signs Your Car Battery Is Draining

There are some signs you can look out for to help you notice your car battery is draining before it dies completely. 

1. Slow-cranking

One sign that your battery is dying or draining is a slow crank. The term “crank” refers to the engine starting.

Usually, when a car starts, it’s quick and all in one motion. When your battery begins to die, the crank can become slow and prolonged.

This is typical because your battery is not providing enough engine to started to begin the ignition process.

There are other reasons for a slow crank, such as a faulty starter or broken spark plugs. But if you are sure there are no other issues with your car, this could be the issue.

2. Dim headlights

Headlights need a battery that’s fully charged to be able to shine its brightest. When you’re driving the vehicle at night and notice that the lights are dim, this could be a sign.

This is especially true if both headlights are dim. If only one headlight is dim, this can be a sign that it’s not your battery but another electrical issue inside your car.

3. Check Engine Light is On

Typically when the battery begins to die, your check engine light will come on, and in some cases, other warning indicators will also begin to turn on.

If you are sure that there are no issues with your engine or the oil in your car, you should inspect your battery.

This is especially true if your check engine light eventually turns off. In most cases, if there is an issue with your engine, the light won’t turn off until it’s addressed.

On the other hand, if a dying batter triggers the check engine light, the light may turn off when the battery begins to charge.

If this does happen, it’s a sign that your battery is draining very quickly but still recharging. It’s likely that your engine will die very soon.

4. Clicking sound or no sound at all

If the battery’s power isn’t enough to start the engine, you’ll begin to hear a clicking sound. This usually comes from under the hood.

Although, if there isn’t any sound and you can’t start the engine as well, the battery may already be dead.

5. Backfiring

Backfiring is kind of related to the first symptom, which is slow cranking.

A failing battery tends to create sparks in the combustion chamber. This would lead to a poor ignition of the fuel.

As a result, the chamber would have a more combusted air-fuel mixture to send to the exhaust.

6. Lack of dome light

A weak door light is also a sign of a failing battery. Although, if the light doesn’t come on at all, the battery could be dead.

There are times when the door wiring could be the problem. One thing you can do to check this is to replace the car battery to see if the lights will turn on.

How To Check If Your Battery is Dying or Draining?

To check if your battery is draining or dying all you need is a multi-meter. 

With a multi-meter you can text the voltage of your vehicle. 

To determine if your battery is draining you need to test your car at different time

  1. After it’s been resting for several hours. I recommend fist thing in the morning. 
  2. After a drive that is at least 30 minutes long.

If you’re battery is not giving you a proper reading after both situations this is a sign that your battery is dying and you should test further. 

A good battery should read between 12.2 and 13 volts when the car is off. 

If the car is running your battery should read between 13 volts and 14.8 volts. 

If you experience anything outside of these ranges this is a sign your car battery is draining and not being replenished. 

It’s important to note that if your engine is reading higher than range for a good battery this is a sign of a faulty battery or issues with the alternator. 

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