Car battery issues? A guide to your car's electrical system

Getting into a car and starting off on a drive has remained pretty much the same over the decades. But these days, everything—the ignition, the air conditioning, the satnav and more—is tied to the electric system of the car, which is the “brain” of it all.

We’re not going to get into every aspect of a modern car’s electrical system because there are just so many variations. But we’ll cover the basics that most of them share so that you can better diagnose any issues with your own car.

Finding your car’s electrical system scheme

To be able to assess what might be wrong with your car, you’ll need to have its electrical system scheme on hand. Luckily, there are numerous sites out there where you can download the right scheme. These sites also tend to have a huge database detailing each component, the possible problems based on the dashboard warning lights and how to fix them.

There are five key aspects of your electrical system:

1. Battery
2. Starter engine
3. Alternator
4. Cables
5. Connectors

The battery is the “heart” of the system, supplying energy to everything else in the car. Its voltage is (unsurprisingly) measured in Volts, while the battery’s capacity uses Amperes (“amps”). It’s important to have an idea of the battery’s voltage: If the dashboard light comes on or you’re experiencing slow starts, it might be low on charge. Batteries typically last about four to five years.

Another key component for quick engine starts is the starter motor. This uses up a high amount of battery in short bursts to get the engine going, with enough revs for the engine to then run on its own. A starter motor consists of a small electric motor, an electromagnet, and a pinion gear. If any of these parts fail, your car won’t start at all.

The alternator transforms mechanical energy into electrical energy via alternating current. This is a crucial function, providing charge for the battery and power for the various in-car devices.

Power travels from the alternator to all of these devices via cables. Typically, red or orange cables carry a positive voltage, and black or green are ground wires. Cables will have different diameters based on the amount of electricity they need to transport. And connectors? Well, simply put, they connect the cables to the devices.

What if my battery goes flat?

If your battery has gone flat after only a few days, there’s likely a problem with the electrical system. You can charge a battery with a dedicated battery pack, or jumpstart it with another car—just remember that you can’t jumpstart a hybrid.

Once the battery is charged up, you can test it with a handheld multimeter: Make sure to connect it to your battery according to the multimeter instructions. If the charge goes up after the engine is running, there may be a problem with the battery itself. Meanwhile, if the charge decreases after start-up, that points to a likely alternator issue. Most auto shops will test either part for free if you bring the car in.

That’s a solid foundation to better understand your car’s electrical system. Interested in reading about other common issues? Check out the Kijiji Autos guide on pinpointing annoying rattles.

Ready to start the search for your next car? Browse thousands of cars on Kijiji Autos’ mobile app to find just the one for you.