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The Main Functions of a Car Battery

CAA Auto Advice July 26, 2023
A technician working on a car, testing car battery.

Batteries are sources of electrical power that make everything from our phones, watches, remotes and even cars work. Even though car batteries are an essential part in making cars start, they also support a few other functions in our vehicles. Find out the main functions of a car battery and how we can help if you ever experience battery troubles.

1. The battery is needed to start the car.

The battery is essentially a huge power reserve that supplies the necessary juice to the vehicle’s starting motor which brings the engine to life with each push of the starter button. The battery also brings electricity to the car’s ignition system.

This helps to explain why a large displacement engine needs a bigger battery than a ride-on lawnmower – the size of rotating mass and electricity requirements are directly proportional. Small capacity batteries, ones which provide a smaller reservoir of electricity from which the car can draw, might be able to fire up a big engine in a pinch but will likely not do so reliably.

2. The battery helps keep electric-powered accessories running like the radio or A/C.

The battery works in partnership with a device in the electrical system called an alternator. On the road, this part supplies electricity to a car’s various electric-powered accessories such as headlights and wipers. On occasion, the alternator cannot keep up with demand – consider a hot summer’s day in the middle of a family road trip when the air conditioning is running, the wipers are on and the stereo is playing.

In extreme – but common – instances like these, the charging system is overworked and needs to call on the battery for an extra jolt of juice in order to keep everything running. If the vehicle has power-hungry accessories added to it such as aftermarket lights and tools (an off-road truck would be a good example), the battery becomes an especially important part of keeping up with electrical demand.

A CAA battery held by a technician.

3. The battery helps stabilize voltage spikes caused by turning on/off accessories that pull a lot of energy.

There is a small but ever-present chance that a car’s electrical system will result in high voltage power spikes, especially when activating or powering off accessories which are a heavy electrical draw. These voltage spikes and instabilities can be partially absorbed by the battery. This protects solid-state components like computers and ignition systems from damage.

Advances are constantly being made in battery tech, with some automakers deploying lithium-ion batteries instead of lead-acid units. The rise of fuel-saving start/stop systems are also forcing battery upgrades to occur thanks to the extra demands being placed on the electrical systems of vehicles equipped with this feature.

Experiencing car battery trouble? CAA Battery Service will come to you.

CAA's Mobile Battery Service¹ will test, replace and recycle your old car battery from your home, workplace or even from the side of the road. Delivery and installation are included at no additional cost.

CAA Members save $25 on the purchase of a new CAA Premium Battery2!