Informational Guide

How Does A Car Battery Work?

In this guide, we answer how does a car battery work, including the construction and chemistry.

You might know how to replace a car battery, but do you understand what makes it work? How does a car battery work and why does it matter?  

If you want to know how does a battery work in a car, we can help you understand. Our guide looks at the battery operation and breaks it down into more straightforward terms.  

How does the battery work in a car? These various stages exist during battery operation.  

The Chemical Reaction  

The 12 volt automotive battery comes with 12 grids, two per cell. One grid contains a single lead element, while the other grid contains lead oxide. The sulfuric acid solution activates a reaction between the grids. The first reaction produces ions that give off lead sulfate and hydrogen.  

The electrons coming from the reaction produce the electricity needed to power the vehicle. These electrons flow around the battery terminals that produce the electricity sent through the cables. This battery doesn’t just emit electrons that produce needed energy, but it also uniforms the electricity supply to keep the vehicle running.  

The Charging System 

How does charging a car battery work? To keep the battery from dying, it must be charged on a continual basis. Without a proper charge, the battery can’t start the engine. While the car is running, the alternator is responsible for charging the battery. This belt-driven system turns the alternator rotor to keep the battery charging. If you're experiencing issues with the battery, you may also need to check the alternator for functionality.

How does a car battery charger work? If the automotive alternator isn’t running long enough to keep the battery topped off, you might want to use a trickle charger. Having a battery without a full charge can leave you stranded, especially if you can’t get the engine started.  

The Energy Storage 

How does a battery for a car work? The storage of the energy is a key factor in how the battery works. As excessive electrons are generated through the chemical reaction, electricity is produced. Aside from being an electrical-producing part, the battery also stores the energy. 

In every battery, there are electrochemical cells where the reactions occur. With the flow of electrons occurring in the circuit, an excess amount of electricity is produced. If the battery is newer, it will store this energy for use later. The stored power combined with the current chemical reactions allows for a consistent flow of power.  

The Electricity Flow 

Understanding how the electricity flows in the battery starts by understanding the chemical reactions first. Each cell in the battery contains two plates or grids, one of lead and the other of lead dioxide. These cells will create 2 volts of energy each. A battery's plates are submerged in sulfuric acid that triggers the chemical reaction.  

When this reaction occurs, lead sulfate and ions are produced. This chemical reaction produces electrons that race around the plates to create electricity. This power flows from the battery terminals so you can start the engine of your vehicle and use the car’s electronics. However, sometimes you may experience a dead battery cell, which can create problems when starting the engine.

jumper cables attached to a car battery

How Is A Car Battery Constructed? (Functionality Discussed) 

  • Battery Terminal/Bushing  
    The battery terminals are connected to the negative and positive strap of the cells. They operate as the interfacing point between the electrical system and the battery.  
  • Battery Acid  
    In a lead-acid battery, the sulfuric acid and water mixture creates battery acid. It’s the high-purity solution that allows electrons to move around inside the battery to create electricity.  
  • Cast-On Strap For Batteries  
    At the top of battery elements, the cast-on straps get welded. It provides the electrical connection needed to the terminals.  
  • Battery Negative Plate  
    Inside the battery, there is a negative plate. It contains a metal grid that holds the lead active material with a spongy feel, and it is separated from the positive plate.
  • Battery Separator  
    Inside the battery, there is a polyethylene material that keeps the positive and negative plates separated. This separator ensures that the plates can supply the proper flow of current where it belongs.  
  • Positive Battery Plate  
    Inside the battery, there is a positive plate. It contains a metal grid that holds the lead dioxide active material and is separated from the negative plate.  
  • Lid On Battery  
    The battery lid is created from polypropylene resin. It is made to be durable and strong, sealing off the battery case.  
  • Battery Case  
    The case around the battery is made from polypropylene resin. It is responsible for holding the cast-on straps, electrolyte solution, and battery plates in place. The case also minimizes the impact from vibrations and extends its life.  
  • Battery Plates  
    Inside the battery, there are stacked alternating negative and positive plates. These plates are connected to the top of the battery by the cast-on strap that gets welded to the plates.  
  • Battery Paste  
    A lead oxide mixture in the battery that combines the sponge lead and lead oxide together. This paste can adhere to the negative and positive battery grids.  

How Does A Car Battery Load Tester & Saver Work?

Now that you understand how does a car battery work, its chemistry and structure, it’s time to look at other functions. How does a car battery load tester work, and how does a car battery saver work? 

The battery load tester is used to determine the health of the automotive battery. It gets connected to the battery and puts it under a load to determine if it is still working as it should. 

Some vehicles are also equipped with a battery saver function. It’s used to prevent the car battery from dying when it’s not in use.  

mechanic putting in a car battery

People Also Ask (FAQs)

How does a car battery produce so much current? 

There are six cells in the automotive battery, each producing two volts, leading to a 12V battery. There are chemical reactions occurring between the plates to create electricity.  

Does a car battery charge while driving? 

The automotive alternator is responsible for keeping the battery charged while the engine is running. As a result, it charges more efficiently when the vehicle is running at highway speeds. If the alternator is functioning properly, it is unlikely that a car battery will die will driving.

Will any car battery work with any car? 

Car batteries are not universal. You need to use the right battery for your vehicle. While it will likely be a 12V battery, it needs to fit in the case that’s located in the vehicle.  

What fluid do you put in the car battery? 

Battery fluid is a mixture of distilled water and sulfuric acid. This electrolyte helps to create the electricity, but it can evaporate over time. If you top off the lead-acid battery with distilled water, you can keep it functioning at its best. 

What percentage of charge does a car battery need to start?  

The car battery needs to be nearly fully charged to start the engine. The fully charged battery reads about 12.6V with the engine off. If the battery reads 11.9V, the battery is completely dead and needs to be recharged.  


While we tried to simplify the basics, you can easily figure out how does a car battery work for kids. A diagram on how does a car battery works, shows you each part of the automotive battery so you can gain a better understanding of what's happening under the hood of your car.