What Charges the Car Battery when Driving?

The battery is the primary source of electric current in the car. It helps electrical power components in the car and even the ignition process.

But without a proper means of recharging the battery, it will soon run out of electric charge, causing a lot of inconvenience.

It is why manufacturers came up with rechargeable batteries charged by an alternator or dynamo.

We have prepared this detailed guide to educate our readers about their battery and charging and answer some frequently asked questions you may come across.

what charges the battery in a car

What charges the car battery when driving?

What charges the battery in your car is the alternator or dynamo in most modern vehicles. The alternator helps to keep the battery from running out of electric charge while driving.

A bad alternator will result in poor car battery recharge and, in some cases, failure to start the car due to insufficient charge. It is also important to note that a bad alternator can damage the battery, as frequent draining will cause sulfur build-up.

Furthermore, the alternator is not electronically powered and does not rely on the battery. Instead, it works by depending on the engine and belt.

The continuous turning of the belt allows the alternator to convert mechanical energy to electrical energy keeping the car battery charging.

How far do you have to drive to fully charge a battery?

The answer to this question is straightforward. On average, it should take 30 to 40 miles of charging a new battery by driving to get it full.

That is, it will take at least 30 minutes of driving on the highway to get your vehicle on a full charge.

If you have the question, “will car battery charge while idling?The answer is yes, it will. The only problem is that the charge might take longer. If you decide to charge your vehicle’s battery by idling it, it could take hours before it is fully charged.

It is preferable if you drive your vehicle to get the battery adequately charged; it will not take up to an hour if you hit the right speed.

Does driving fast use more battery?

Yes, the faster you drive, the more energy the electric components may need. When your vehicle consumes more energy when driving or speeding, it has nothing to do with the engine. Apart from the ignition process, the engine does not need a battery when running. However, the electrical components still rely on the battery.

You must understand that the faster you drive, the more electric components like the air conditioning and heater work, which means a higher electricity consumption. The good thing is the more energy consumed by these components is needed to drain the battery. As the car speeds and the electric energy consumption increases, so does the alternator supply more electric current to the battery for charge.

Does driving charge a battery faster than idling?

Yes, driving gets battery charged faster than when idling your vehicle. The reason for this is that your automobile generates lesser RPMs when idling.

The alternator depends on the vehicle’s speed to generate electricity to charge the battery. The faster the car, the more the engine can rotate the alternator. When the engine can move fast enough, the alternator can generate enormous energy to charge the battery more quickly. It is why the battery charges faster when driving on the highway or at high speed.

On the other hand, when idling a vehicle, it has a lesser RPM when compared to a car that is driven. When you idle a vehicle, it has between 600 to 1,000 rpm, depending on the type of vehicle. When driven on the highway, an average vehicle has an RPM of around 2,000 and more, depending on the car. These RPM differences show how fast the engine can spin the alternator to generate energy.

Can a car battery drain while driving?

Your car battery can drain while driving, and it is due to some factors. The alternators keep car battery charged whenever you are driving. The alternator starts the charging process when you switch on the engine. It does not allow the battery to drain; however, some factors can make the battery supply more electric energy than the charge receives and reduce or stop the charge given by the alternators. When this happens, the car battery will die when driving.

Some factors that could cause the battery to get drained while driving include the following.

1. High-performance light

Some aftermarket lights, like the high-performing ones, tend to consume more electric current and can drain the battery faster. Many people have too many of these lights used in their vehicles. As a result, when the alternator is charging your car battery, the battery is expending more electrical current than the alternator is providing.

2. Extreme weather

One of the biggest enemies of your battery is extreme weather conditions. It will affect the battery’s performance, whether it is too cold or hot. Extreme cold weather conditions cause a slow charge for batteries, which makes them drain faster when driving.

3. Old battery

When a battery becomes too old, it cannot hold as much charge as it used to. The battery has many build-ups, and the chemical components are weak and cannot hold a charge. When you drive with a battery you have been using for over 4 years, expect that it will drain while driving.

4. Defective diodes

When the alternator has a defective diode, it will drain the battery faster when you are driving. Do well to check the diodes.


Now that you understand that it is the alternator responsible for charging the battery while driving, you could easily link your fast-drained battery to alternator issues or other related problems. Also, change your vehicle battery after using them for at least 4 years. It will prevent you from having a drained battery while driving.

Akindayini Temiloluwa

I am Akindayini Temiloluwa, an automotive expert writer and car enthusiast. I have over three years of experience in the automotive writing niche and have completed over 300 pieces of content from 50 projects. I have vast knowledge and skill in vehicle repairing, all mechanical work, car upgrades and maintenance. My goal as an automotive content writer is to simplify the most challenging concepts for my readers, help them self-diagnose what may be wrong with their vehicles and offer real value for their time.

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