None of the motorists can deny the importance of a car battery. However, every car owners and drivers should know that how a car battery works. After knowing the working principle of a car battery, you will be able to repair and diagnose the problems in your car battery. I will try to explain the working of a car battery in a simple way. So, every person can understand the basics of a battery of a motor car. Let’s start;

How a Car Battery Works

We will see here the operating principle of a car battery, that is to say, a led battery.

Basic principle

Like any battery, and whatever its technology, it is a matter of recovering the electricity produced by a chemical reaction. The advantage of a battery (unlike a battery) is that the chemical reaction is reversible. In fact, once the reaction has taken place then the battery is flat and there is nothing to expect from it. However, everything can reset by reinserting electricity (roughly) inside (the chemical reaction then goes backward, setting everything back to zero.

Battery Components

Three main elements can be distinguished in the batteries:

The electrolyte consists of sulphuric acid. It is in this liquid solution that the electrodes bath.

You can Read More About: How to charge a car battery without a charger

Electrode (terminal+) so-called cathode which tends to want to take/attract electrons (the grains of electricity which also serve as the shell for atoms, the grains of matter which form everything), it attracts them naturally because it makes a bit of it to be stable. Because each atom has a positive nucleus ( + ) and electrons that revolve around negative ones ( -). When the positive and the negative are not equal, there is an imbalance that will be either negative or positive, hence the fact that some materials attract electrons and others reject them. On the battery of a car, the cathode will be a” rod ” of lead dioxide (i.e. lead coupled to dioxygen: two oxygen atoms together)

Read More About: Weight of Vehicle Battery

Electrode (borne -) anode that tends to give electrons. It’s just lead.

Note that the anodes and cathodes must not be in direct contact, because there would be a short circuit. The result is a real small chemical plant that can generate electricity when there is a chemical reaction between the anode, cathode, and electrolyte. But to trigger it, you have to put the anode in contact with the cathode, that is to say, to operate electrical organs.

Read More About: How a Car Engine Works

Chemical Reaction: the landfill

By putting the two terminals in contact (we are therefore using the battery), the electrons (the electricity, therefore) of the anode ( – ) will want to go towards the cathode ( + ) because of the property of the materials explained above. Unfortunately, when electrons leave from one electrode to another, it causes a chemical imbalance (“shell fragments” of atoms, electrons, are missing !). And it’s all going to have to balance out somehow.

As a result, everything will return to balance (I’m not going to go into the details of the mutation) through a chemical reaction.


The cathode ( + ) that was lead dioxide will become lead sulfate

The anode ( – ) that was made of lead would also become lead sulfate

The bath in which all this is bathed (the electrolyte) is transformed in large part into water (H2O) but a small part remains in the state of sulphuric acid

When the two electrodes became lead sulfate, there was no differential between them. Basically, the cathode attracted electrons and the anode gave them thanks to the properties of the materials that made them up, but now we’re dealing with two similar materials. And then the electrolyte is now mostly water.

Chemical reaction at Recharge: electrolysis

When it comes to charging, it’s all going the other way. So we’re going to inject electrons into the anode and take them back to the cathode, which will force the reverse reaction. Once done, we can go back the other way, that is to use the battery.

Cells /accumulators?

To form a battery of 12 v, there are actually 6 cells of about 2 volts, which then provides 12v because of 6 X 2 = 12.

Why lead?

Why are we still using lead-acid batteries, which seem archaic compared to lithium? Well, the lead-acid battery allows much more recharging/discharge cycles and it also provides a higher current intensity (important to operate a starter motor, which has to fight to drive the engine with high compression). Unfortunately, their defect is that they are more cumbersome.


As long as it is not subjected to so-called “Deep” Discharge (When it is flat), the latter can undergo thousands of cycles. However, after about 20 deep/total discharges, she will give up her soul.

Read More About: What can Drain a Car battery when it’s off

It must be understood that when it empties, there is a formation of lead sulfate crystals on the electrodes: if one waits too long before recharging, these crystals will not return to their initial state. It’s the sulfation.

In addition, the water and sulphuric acid that make up the electrolyte (the liquid in which everything is Present) do not mix very well. If the settling lasts too long (a car without any movement for a long time), the mixing will not be as easy to do. It’s stratification.

Over time, the electrodes wear and break down. Hot weather countries accelerate this phenomenon, knowing also that sulphuric acid (thus acid) remains corrosive.


Characteristics of a battery


It’s the voltage. Less easily understood than the Ampere, it is basically the “amount of electricity that can be generated”.

Read More About: How to Test a Car Battery


The amperage uses to determine the intensity of the current passing through a cable. The more intensity there is (and thus amperes), the more electrons pass through. The more there are, the more the metal will blush because it will cause heat. It is the friction of the electrons, very numerous, which compress to each other. it can be compared to the pressure in a garden hose, the stronger you put, the more pressure there is.

Read More About: How a Car AC works

The data on a car battery indicates the number of amps it can release for 30 seconds under temperature conditions of -18°. The greater the number, the greater the force delivered during these 30 seconds. So if your car tends to have trouble getting started, try to take big caliber with this data.

As per my knowledge, I have explained how a car battery works. If I forget to mention anything else please do comment in the comment section.

Leave a Comment