This is how your car battery works

Car batteries may look simple on the outside, but there’s a lot of chemistry going on beneath the surface to create electricity to for your vehicle.

Batteries are an important part of everyday life in the 21st century because, quite simply, most of the devices that we rely on every day for work and play won’t function without one. The same goes for the big battery in our vehicles that run all the onboard electronics and help start the engine. For such an important item, it’s a good idea to know a bit about how it works.


Aside from firing up the car, the battery is responsible for powering the air conditioning system, radio, windshield wipers and all the interior and exterior lighting. Features like automatic seats and windows also need the battery to operate their auxiliary motors.


Like any household AA battery, a conventional lead-acid 12-volt car battery has a positive (+) and a negative (-) terminal that is appropriately labelled on the outer casing. You can also differentiate between the two terminals by the colour indicator: red for the former and black for the latter.



Batteries create power through a chemical reaction. Made up of six cells, each cell contains two electrodes comprised of overlapping metal plates forming a positive and negative grid. The positive grid is covered in lead oxide, which brings electrons into the cell. The negative grid is covered in lead and releases the electrons. This occurs when the metal plates— submersed in a water and sulphuric acid mixture — react with the lead oxide and lead, thereby creating electricity.



Most car batteries will last for up to four years, although performance will slowly deplete over time. Constant draining and recharging of the battery, for instance leaving the headlights on with the ignition turned off and then jumpstarting the car afterwards, can reduce this timeframe considerably. Wondering if it’s time to replace yours? Ask your service department — they have tools to diagnose the health of the battery.


• The first vehicle battery was created in the 1800s.

• In 1911, the electric horn was invented, followed by the electric starter a year later. Prior to this, engines were started using a hand crank.

• The sealed-beam headlight came on the scene in 1939.

• Starting in the 1980s, new comfort and convenience options were introduced requiring more electricity. Thus, battery design improved significantly providing increased capacity to meet the needs of the new technology.

Posted by Benjamin Yong

Benjamin Yong is a freelance journalist and communications professional living in Richmond, B.C. He is often found writing about cars and the auto industry, amongst other things, or driving around in his work-in-progress 1990 Mazda MX-5. Twitter: @b_yong Instagram: @popuplights