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Why Do Cars Need Batteries?

Why Do Cars Need Batteries?

Have you ever wondered why cars rely on batteries? We often take for granted the vital role that a small, unassuming device plays in the functioning of our beloved vehicles.

Cars need batteries to provide the necessary electrical power for various functions and systems. The battery is responsible for starting the engine by providing the initial electrical energy, as well as supplying power to components such as the lights, radio, air conditioning, and other electrical accessories when the engine is not running.

In this article, we delve into the fascinating world of automotive batteries, exploring their crucial functions, the science behind their operation, and why they are an indispensable component of every car on the road.

Buckle up and join us on this electrifying journey as we uncover the captivating secrets behind why cars need batteries, unraveling the mysteries that make our automotive world go round!

Can a car run without a battery?

There are two answers to this question, and it will depend on whether the car has already been started or not. In order to start the vehicle, you will need a battery. But once it has been started, you may be able to continue running it without the battery itself.

Let’s say the engine is not turned on, and the car has been sitting for a while. The battery is completely dead and has no power at all, but you know the alternator is good. 

Unfortunately, you won’t be able to start the vehicle in this condition. A battery is vital for providing the first jolt of power that gets the rest of the engine and inner components working.

This is why jumpstarting a dead battery with another vehicle that has a good powerful battery is able to get you back on the road in a short amount of time.

The alternator itself can provide enough power to run the vehicle without the battery but doesn’t contain enough power itself to actually start the car. The battery provides a spark of stored energy to the ignition coil, which then ignites the fuel being passed into and through the engine. This form of controlled combustion is how an engine runs.

So what if the vehicle is already running? In this case, the battery is not used nearly as much as you might think. With a good working alternator taking over the task of producing electrical energy, the car can continue to run as normal.

In fact, an alternator can even recharge a dead or low battery!

While this won’t happen instantly, it can normally recharge a battery over 30-45 minutes time so the next morning, when you need to start your vehicle, your battery should have enough power to do so.

Functions of a car battery

Functions of a car battery

The main purpose of a battery is to get your engine started. The battery creates a powerful and sudden burst of energy that gets your ignition system running.

Once this is running, the alternator joins in on the task of keeping your vehicle running!

One thing to keep in mind, however, is that the battery is responsible for running a large number of accessories on and inside your vehicle since most alternators won’t have enough power to do so, especially if they are running the vehicle without a battery installed or while in the process of recharging a battery. 

This includes the horn, headlights, any security systems, automatic windows, and dashboard indicators.

While the alternator can keep the main engine running, it usually does not have the right amount of power to keep those electrical systems going while also recharging a battery.

If you are using your alternator on a running vehicle to recharge a dead battery, you can test the battery progress by trying headlights, interior lights, and the horn.

Why do gas cars need batteries?

You might think a gas car can get by with just the fuel alone, but this is not true. In order to get a car started in the first place, a battery is a requirement.

The spark at the start is the main purpose of the battery in a gas-powered car. Once the engine is started, the battery can actually be removed, and the vehicle can still run.

This will depend on the alternator, however. Since the battery provides electricity to the ignition system, which then starts the combustion process, the alternator kicks in to pick up on power generation.

What happens when the car battery is low?

1. Engine struggles to start

A low battery can have an immediate impact on how quickly your vehicle starts.

If you notice it attempts to turn over but sounds a bit sluggish, it may be a sure sign of a low battery.

Since the battery is wholly responsible for the initial burst of energy needed to start the car, a low battery can cause issues with this process leading to a slow or struggling start.

2. Engine won’t start at all

Having a very low or completely dead battery will cause the engine to not be able to start at all.

When you turn the key or press the start button, you may only hear a repeated ticking sound coming from under the hood. This is the ignition system attempting to start the combustion process but not getting the jolt of power it needs from the battery.

In this case, the easiest solution is to get a jumpstart from a neighbor that has a good car battery installed or buy a new battery entirely.

3. Headlights are dim

Headlights are normally run by the battery itself and not the alternator.

This makes them a very early warning system for a low battery, especially at night.

If you are driving at night and notice your lights are dim or flickering, it could be due to a low or failing battery!

4. Engine backfires

While this is normally due to other issues such as poor fuel combustion, improper fuel mixtures, or cylinder issues, it can also be due to a low battery.

Since the battery isn’t providing ample amounts of sparks to the rest of the engine, gas can collect in the engine and build up without being utilized properly.

When finally released, it causes a backfire and is a potential sign that the battery is low or failing.

If you found this article helpful, make sure to take a look at some of the other battery-related posts linked below!

Zach Reed

Hi, I'm the founder of! Having owned a wide variety of vehicles in my life, I was astounded at how hard it can be to find answers to common automotive questions. Rather than sit idly, I decided to create this website to help others!