Though your car is equipped with an alternator (a generator, that converts rotational mechanical movement in to electricity), it needs a battery to store the generated electricity. This stored electricity is necessary to start your car, provide power to accessories when the engine is not running, and to power essential lights when necessary prior to starting the engine. The battery also provides a small amount of power to your audio system, remote locking system, ECU, and your car clock, to keep them running even when the car is locked and not in operation.
How the car electrical system works:
Car batteries are responsible for providing the charge to crank and start the engine. Batteries operate based on a chemical reaction – acid and lead in the battery create a chemical reaction, which is then turned into an electric charge and stored in charging plates within the battery itself.
When you turn the ignition switch, several things happen, but all of them require voltage from the battery. When the ignition is switched to on, electricity is sent to the main relay, and from there to the fuel pump (which sends petrol to the engine for ignition), and the ECU. The battery also produces electricity to feed the spark plugs (in petrol models), which ignite the fuel, and turn your car’s starter, which is responsible for actually turning the engine and initiating the combustion process. If your battery is dead, none of those things will happen. Depending on the amount of electricity left in the battery, you may have just enough power to turn on a few lights, or you may not even have enough for that.
Possible Root Causes why your Car Battery could have gone dead:
- Dead Battery: Batteries have a finite lifespan. Most last between four to five years, while others die sooner. All will eventually die and need to be replaced. This is a normal part of vehicle maintenance, and your battery, starter and alternator should be tested regularly to ensure that you’re not stuck on the side of the road with a dead battery.
- Car Lights Left On: With the advent of smarter automotive technology, this has become rarer, but it still occurs. If your car’s lights don’t have an automatic shut off feature, they’ll stay on unless you physically turn them off. If this happens and the engine isn’t running, they’ll drain your battery completely.
- Door Not Fully Closed: If your door is open, then the cabin light will be on, and other interior lights may also be on. These lights draw their power from the battery if the engine isn’t running, and can quickly drain a battery.
- Faulty Alternator: The alternator produces electricity while the engine is running, and is responsible for providing all the power needed for your engine, your accessories, and to recharge the battery. If the alternator is faulty, it won’t charge the battery, and all the power needs of your vehicle will come straight from the battery. Eventually, this will drain it completely, leaving you stranded.
- Faulty Starter: A faulty starter will not crank the engine, and therefore will not help start the engine.
- Faulty Main Relay: Sometimes, everything in the charging system is perfectly fine, but your car still won’t crank. In this instance, the first suspect should be the main relay, since it controls the fuel pump and the car’s computer.