Can you drive a car without a battery? [with Pdf]

Yesterday my friend asked me the same question, “can we drive the car without a battery?” at that time I also get confused about it, therefore, we both took the help of the internet to find a satisfactory solution. By doing this small research we got the following results that we have shared below.

You may be able to drive the car without a battery only if the engine is already started before removing the battery. But it is not possible to start the car without using the battery.

Before moving towards our main question let’s know what is the function of the battery and alternator in automobiles.

Can you drive a car without a battery

What is an automotive battery and its function?

It is the rechargeable battery used in a vehicle to supply power to vital operations like cranking of engine, spark generation by the ignition system, etc. In the running condition of the engine, the battery gets recharged by the alternator.

The automotive battery performs the following main functions:

1) Provide power to the starter motor: Cranking is essential to job to start the engine that is performed by the starter motor. The battery provides power to the starter motor, therefore, it can perform cranking operation, and then only the engine starts its working.

2) Provide supply to the ignition system while starting of engine: The battery also provides supply to the ignition system till the alternator will start to generate electricity.

3) To operate glow plug: In the case of a diesel engine, the glow plug helps to heat the air inside of cylinder in the cold season. Without heating the intake charge it is difficult to start the engine therefore the battery helps to provide supply to the glow plug.

4) To power all accessories: Even when the engine is not in running condition, the battery provides supply to the all accessories like headlight, indicators, security system, horns, etc.

What is the function of an alternator in the car?

The alternator is powered by the crankshaft through a belt or chain. The alternator is used to convert some part of the mechanical energy of the crankshaft into the electrical energy.

Here we have mentioned some of the major functions of the alternator.

1) Provide supply for spark generation: When the engine gets started, the alternator provides an electric supply to the coil of the ignition system therefore the spark is generated by the spark plug to start the ignition process.

2) Charging of battery: It is one of the main functions of the alternator to charge the automotive battery as the battery helps to start the engine from rest.

3) To supply power to the various accessories: In the running condition, the alternator provides power to the accessories like wipers, air heaters, power windows, heated seats, headlights, etc.

Can you drive a car without a battery?

The answer to this question depends on the condition that whether the engine is already started or not. For both conditions answer is different. Let’s discuss each case.

Case I) If the engine is in stopped condition:-

It is necessary to provide cranking to the engine when the engine is at rest as well as the ignition system also requires an electric supply for the generation of spark.

The battery supplies stored energy to the starter motor and to the ignition coil for starting of engine therefore battery has a great importance while starting the engine.
Therefore if the battery is detached from the car before starting of the engine then you can’t drive the car.

Case II) If the engine is already started:-

In this case, the engine is already started hence the alternator also has started the generation of electrical energy. This electrical energy is utilized by the ignition system for spark generation and also utilized by other accessories of the car.

Now if the battery is detached from the car after starting the vehicle then the engine will never stop it’s working as all the accessories which work on electrical energy are now powered by an alternator.
Therefore the engine will continue to run until it gets stopped by the driver.

Is it really Safe to drive the car only on alternator?

The battery provides a constant supply of an average of 12 volts and it, does not generate voltage spikes therefore the car accessories and electronic components remain safe.

The alternator never provides a constant voltage supply. It provides a High voltage spike while working. Therefore this high voltage spike can damage the electronic components used in the car. Hence it’s not safe for the car accessories to run the car on alternator only.


From the above discussion, we can say that the engine will run without the battery only if the engine is already started before removing the battery.

Pratik is a Graduated Mechanical engineer. He enjoys sharing the engineering knowledge learned by him with people.

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