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7 Things That Can Drain Your Car Battery [Updated 2022 List]

What Can Drain A Car Battery When The Car Is Off

Dreaming about Pennywise or Freddy Krueger may be terrible.

But do you know what my nightmare scenario is?

Driving while already late for an appointment…

Only for my car to screech to a halt. With its battery dead.

So to avoid that…

I researched what actually drains car batteries.

Continue reading to find out:

  • 5 signs that your car battery’s dying.
  • The number 1 cause of car battery drain.
  • 7 things that can drain your car battery and how to avoid or fix them.
  • And a lot more…

What can drain a car battery when the car is off?

Leaving the headlights on can drain a car battery when the car is off. It only takes 2 hours for the headlights to drain a fully-charged battery. Also, your car may have parasitic drains. These are car components that continue to use the battery even after you switch off your car’s engine.


7 things that can drain your car battery


#1: Human error

Human error is the number 1 cause of car battery drain.

Here’s a scenario as an example.

If you’re a long-time vehicle owner, this has likely happened to you a few times.

You switched off your car engine. Stepped out of the vehicle. And locked it.

Only to realize that you forgot to turn off your headlights.

Now on average, it’ll only take the headlights 2 hours to drain a fully-charged battery.

So if you realize it too late, your battery’s dead.

In addition to headlights, interior lights and car radio are 2 more components to watch out for. As leaving them on will also drain your battery significantly.

Manufacturers have actually attempted to solve this problem via car alerts.

Basically, you’ll get notifications when you forget to turn off any of your car components.

But if you’re driving an old model, it’s always best to be mindful.

Double or even triple-check everything before leaving your car.

#2: Parasitic drain

“What exactly is parasitic drain?”

A parasitic drain is when your car’s electric system continues to use the battery. Even when the entire engine’s not running.

And no, this isn’t the same as leaving your headlights on.

This is actually harder to diagnose. As most of the time, you won’t see which car component is actually causing it.

While it’s best to have an expert pin down the cause of a parasitic drain…

You can also do something to minimize it. Such as ensuring that you unplug all external devices. 

Including chargers or speakers.

And while FM transmitters won’t really drain your battery…

You may also opt to remove them when not in use.

#3: Defective alternator

Defective Alternator

An alternator is what provides electrical power to your vehicle.

It’s also responsible for charging your car’s battery while you’re driving.

An alternator also usually requires little maintenance. It can last over 10 years. And over 250,000 miles.

However, your car battery will also suffer once the alternator starts breaking down. Since it’s your car battery’s only power source.

So watch out for signs of a faulty alternator. These include:

  • Frequent stalling.
  • Weird engine noises.
  • Flickering headlights.
  • Dashboard indicator light warning.
  • Electrical issues such as difficulty opening windows.

Note: Replace the alternator as soon as you notice any of these.

#4: Loose battery cables

Battery cables are also called clamps or terminal ends.

These are the rings that connect the battery to the car. And when these cables are loose, the battery won’t charge while you’re driving. Causing it to drain much faster.

That’s why it’s crucial to check under the hood frequently.

It’s easy to spot if the battery’s cables are loose. Just try to wiggle them to see how easily they come off.

Important note: If you try to remove the battery cables, always start with the negative. It’s the black one. This is to avoid shorting the car battery.

Now if the cables are too loose, you may wrap them with aluminum.

You may refer to this video on the proper way to do it:

In addition to being loose, battery cables may also experience corrosion.

And baking soda and warm water are effective in removing them.

These are the steps:

Step #1: Apply baking soda all over the corroded area.

Step #2: Add some warm water to trigger the chemical reaction. This chemical reaction is what will remove the battery terminal’s corrosion.

Step #3: Once the corrosions clear up, wipe the terminal clean. You may use a dry cloth or a scrub sponge to do that.

#5: Extreme temperature

Extreme temperatures are also harmful to your car’s battery.

By extreme, I mean anything less than 10 degrees Fahrenheit (-12 degrees Celsius). Or over 100 degrees Fahrenheit (38 degrees Celsius).

When you expose your car to these temperatures for a long time… 

The battery will start having chemical reactions. Which will eventually damage it.

So ensure that your car garage has the proper insulation.

In addition, here are some of the things you can do to protect your car from extreme weather:

#6: Battery age

On average, car batteries last around 3 to 5 years.

So at some point, your car battery’s age will show signs of wear and tear. Regardless of how well you take care of it.

And if the battery’s old, it’ll be unable to hold a full charge. Therefore, making it drain faster.

The key is to recognize the signs of wear and tear.

These are just some of the indicators that your car battery’s dying:

  • Dim lights.
  • Damaged connectors.
  • Harder to start your car.
  • The check engine light’s on.
  • A terrible smell when checking under the hood.

Once you notice some of these signs, take your car to a mechanic. And look into changing the battery.

#7: Short drives

Some might think that long drives are bad for the car battery’s health.

But the truth is…

It’s the other way around. Frequent short drives are actually more harmful to your car’s battery.

And by short drives, I mean driving around for 20 minutes or less.

“Why so?”

Well, starting a car engine takes up a significant battery charge.

And once you’re driving, the alternator starts recharging your battery.

So for short drives, the alternator won’t be able to charge your battery enough. 

Do it often, and your battery will die sooner than it’s supposed to.

In addition, frequent start and stop will wear out your battery much faster.

So how do you avoid this problem?

Plan your trips accordingly.

For instance, instead of going to the grocery store every few days…

You should do it once a week. Or every other week, instead.

Moreover, you may consider walking or commuting instead if it’s convenient enough.

Using your car less often will not only extend its battery’s lifespan. 

You’d also be helping our environment with fewer pollutants from your car’s emissions.