How a Battery Works With a Car's Electrical System | YourMechanic Advice

How a Battery Works With a Car's Electrical System

Have you ever wondered how your car’s electrical system works? It all starts with your car battery.

Your car's electrical system operates on a closed circuit, with the main power system being the automotive battery. It uses less than the typical household current, and yet still manages to operate all the functions of your vehicle, including your headlights, window defoggers, turn indicators, aerial, fan, heater, washer pump, locks, sensors, and gauges, and more.

About your automotive battery

All that electricity flows along one cable running from your battery to the component that it powers, and then back to the battery through the metal body of your car. This is called a negative earth return system. That, essentially, is how car batteries work to make your car electrical system function.

What happens if your car battery voltage drops?

If the voltage drops, then your car's electrical system doesn’t work properly. You might find that your windshield wipers are sluggish, your windows don’t go up and down as quickly as they should, or even that your car is reluctant to start when you turn the key. That’s because some components will only work if they’re getting a high enough voltage.

The starter motor

Your battery also delivers electricity via a heavy cable to the starter motor. The starter is what activates your spark plugs, powers the alternator, and delivers power back to the battery.

This is a pretty simplistic explanation of how car batteries work with your car’s electrical system. The fact is that this is far too complex a topic to deal with in the space of this brief article. Modern cars can contain literally miles of wiring in the car electrical system, and this isn’t really a topic for a backyard mechanic, although it is a good introduction for someone who is curious about how car batteries work in the context of the whole vehicle.


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