car battery work

How does a car battery work?

Car batteries are responsible for powering the whole vehicle. If the battery isn’t working, neither is the rest of the car. So how is it that one small battery provides enough juice to start a whole car and keep it running?

Car batteries run on chemical and electrical energy. There is an electrical circuit connected to the outside of the battery that charges the battery and allows electrons to flow. There are also chemical substances within the battery that form chemical reactions with each other and the electrons. Electrons act as the subatomic particle that activates the battery, allowing it to power up the car’s engine.

If you’ve always wondered how a car battery works, this article is for you. Keep reading to find out everything you need to know about how a car battery works.

How A Car Battery Works

There are three components within the battery, namely two connectors known as an anode and a cathode and then a chemical solution that the connectors sit in. An electrical charge from outside the battery charges it and activates a chemical reaction within the battery.

The chemical energy is converted to electrical energy; thus, the battery powers up.

The anode is a positively charged electrode within the battery, which allows the electrons to travel outside of the battery, and the cathode is the opposite, the negatively charged electrode through which the electrons re-enter.

Chemical reactions between the chemical solution within the battery and the anode and cathode each are what allows the movement of electrons to occur. The electrodes are contained in the chemical reactions that occur between the solution and the connectors.

The Physics of How A Car Battery Works

From a physics standpoint, a battery is made up of three basic types of components:

  • A separator
  • An electrolyte
  • Two electrodes

The two electrodes are specifically called the anode and the cathode, and both are made up of conductive materials that allow electrical current to pass through them. The two electrodes serve different roles within the battery.

The cathode attaches to the battery’s positive end. The positive end is also where the current comes out of the battery. This happens when the power within it is being discharged, or when power from the battery is used.

While the battery is discharging, electrical current comes into the battery on the opposite end, the negative end. This side is called the anode.

The electrical current is not to be confused with the electrons, mainly since they are discussed in more detail in the next subheading. When the electrical current is entering through the anode, the electrons are exiting through it. Hence they are moving in opposite directions.

Between the electrodes inside the battery, and inside them as well (since the electrodes are both sponges that also absorb the electrolyte mixture) is the electrolyte.

These particles, also known as ions, combine and react with the material that each of the electrodes is made of, and a chemical reaction is obtained. The chemical reaction allows the battery to generate an electrical current that can power the things connected to it.

The battery receives the electrical charge from the car’s alternator. The alternator Is a component made up of a magnetic coil and rod, inside the car’s engine, that converts the mechanical energy into electrical energy.

The electrical energy is fueled through the battery, giving it a charge. The battery is then able to, in turn, power the electrical components of the car’s engine, most notably the starter, without which it I impossible to start the car.

The Chemistry of How A Car Battery Works

To understand the chemistry of how the car battery works, we must first understand the chemicals that exist in each of the components in the battery. All of the chemicals found inside the battery contain some combination of hydrogen, oxygen, sulfur, and lead.

  • The chemical solution – Sulfuric acid given as H2SO4 (which is a compound of hydrogen, sulfur, and oxygen)
  • The cathode – lead dioxide given by the chemical annotation PbO2 (a compound of lead and oxygen)
  • The anode – Lead, which is represented by the chemical annotation Pb

The battery stores energy in a chemical form and converts the chemical energy into electrical energy. The reaction is offset by the external connection of the electrical cable that sends an electrical charge through the battery.

The cathode, a sponge, composed of lead dioxide and the chemical solution pf sulfuric acid within the battery in which the two connectors sit, react together to produce a lead sulfate

Here’s an equation to show how this happens:

What we see from this formula, if we are to break it down into laymen’s terms, is that when the electrons from the electrical charge passing through the battery terminal interact with the lead dioxide of the cathode and the sulfuric acid of the chemical solution, lead sulfate, and heavy water are the byproducts.

On the side of the anode, the lead in the anode reacts with the sulfuric acid in the chemical equation. The interaction of the two chemicals creates lead sulfide and electrons.

The electrons are essential in the chemical reaction that happens on the cathode side; however, the electrons cannot travel through the chemical formula to the cathode. They must instead move through the external electrical circuit and back into the cathode.

The equation gives this chemical reaction:

These two chemical reactions work in a loop, one feeding the other and vice versa, powering the battery and allowing it to charge the car engine.

How Long Does A Car Battery Work For?

The average life span of the battery of a car is three years. This period, however, is affected by numerous factors that also need to be considered.

Because a large portion of the battery working has to do with the chemical agents inside of it, environmental factors that would generally affect these chemical agents are also environmental factors that can affect the battery. An excellent example of this is temperature.

When there is cold weather, the car needs to be started and left to run for a little so that the cold does not put a strain on the battery. This kind of strain on the battery can weaken the battery and give it a shorter life span than was initially anticipated. And could potentially cause your car to break down on the side of the road.

On the flip side, heat tends to take a more significant toll on the performance and the reserve of the battery. Hot weather can cause the liquid inside the battery to evaporate and can also cause additional internal damages.

Once the heat has weakened the battery, it is more vulnerable to break down in freezing temperatures because it does not have the resistance to deal with profound changes in temperature.

Another thing that can kill your car’s battery is leaving it dormant for too long a period. This will cause all the charges to go out from the battery before the next time the car is driven. To solve this problem, you need a dead battery recharge by removing the battery and charge it, then replace it in its location before starting the car again. Here is a guide to know how to Dispose of Your Car Battery properly when its out of service.

How Does Charging A Car Battery Work?

As mentioned above, while the car is running, the battery is charged by another component of the engine, which is called the alternator, converting mechanical energy into electrical energy to source through the battery. So usually, the battery does not need to be specially charged.

The battery, on its own, discharges electrical energy into the rest of the car and so it needs a source of electricity to keep the voltage at a certain level for the car to keep running.

The voltage of the battery is the amount of electrical power that the battery is producing. Most car batteries run at a voltage of 12. But the battery has to have a voltage above 10.5 volts in most cars for it to be able to power the car’s engine.

The battery has something called a reserved capacity. Reserved capacity establishes how long a battery can discharge at a rate of about 25 amps in the case where there is a fault in the connection between the alternator and the battery, as the band breaks.

It is a measure of how long a battery can last if it is unable to receive a new charge from the alternator consistently while the car is running. However, once the voltage drops below the 10.5 marks, the battery needs to be recharged.

So, in the situation where the battery is not receiving a charge from the alternator, because of an issue in the connection between the two parts, an external source will need to be used to charge the battery. This is not sustainable: one does not work without the other for very long.

The alternator will need to be replaced, and the whole engine inspected to make sure the problem is not more severe. If the issue is the belt that connects the two parts, then an engineer can replace the belt and mend the connection.

Besides this, the battery can be charged in one of two ways. You can connect two cables directly to the battery called “jumper cables” to jump the battery, or you can disconnect the battery from the car and connect it to a charger.

If you want to jump or to charge the battery, you must first turn off all the lights and components customarily connected to the battery and run some maintenance on it. Remove the negative cable or the ground cable first. This is always a black cable unless the cable has been replaced over the years.

Even if the cable has been replaced, you can identify it as the cable labeled with the negative charge. Remove the cable annotated to the positive charge next.

If any battery acid has poured unto the outside of the battery, clean the terminal with a terminal cleaning brush and mixture of water and baking soda to neutralize the acid.

Wear protection for your eyes, nose, and mouth. If the battery has removable caps, carefully pry them off to check the water level. If the water level is low, add distilled water only to the full mark. Note that this is not required for all batteries, so if no cap exists, overlook this step.

To jump the car, the jumper cables will connect to the dead battery and the working one that will be used to charge. Hook up the positive cable, which is red, to both batteries, starting with the dead one first, to the positive side of the battery. Then connect the black wire (the negative charge) in the same order. Start at the lowest charge and build up to the charge best for your battery gradually.

Equally, if you plan to charge the battery, remove it from the car and place it in a sturdy and safe place. Connect the charger with the red wire first, then the black.

Start at the lowest charging rate and work up to the most ideal on. If you want any help, check jump start costs and get a professional to assist you in charging the car in their shop if you fear mistakes. Turn the charger on and set a timer to full charge.

If you want to learn more about the functions of a car battery, check out that article for more information!


To conclude, car batteries receive electrical energy, convert it into chemical energy, then back into electrical energy used to start the car’s starter and other electric components. If you need further assistance with your car battery, look for a “mobile mechanic near me” to help you out.

Furthermore, if you are ever in a situation where you don’t know how to charge your vehicle’s dead battery and you need further assistance, Mach 1 is here to help!