Where Does Car Electricity Come From?

[JoshuaAnn]

Car electricity comes from the vehicle's battery and alternator. When the car starts, the engine activates, and once the engine is running, it transfers power to the alternator via a belt, thereby driving the alternator to operate. A car battery is a device that converts chemical energy into electrical energy, functioning as a DC power source. Its roles include: 1. Assisting the alternator in supplying power to electrical devices when the alternator is overloaded; 2. Providing power to electrical devices when the engine is idling. The car alternator serves as the primary power source of the vehicle, supplying electricity to all electrical devices and simultaneously charging the battery while the engine is running normally.

[VonColton]

After driving for over a decade, I finally figured this out. I used to think the battery did all the work. Actually, a car's electrical system operates in three phases: When you first turn the key, it's entirely powered by the battery, especially for starting the engine which requires a huge current; once the engine is running, the belt drives the alternator to power everything - headlights, AC, radio all run on generated electricity; the clever part is the alternator both powers the system and recharges the battery. After parking and turning off the engine, small devices like the alarm clock still rely on the battery - but you can't carelessly leave headlights on then. Once I forgot to turn off the dome light and needed a jump start the next day.

[AlexanderAnn]

When repairing cars, people often ask me why the battery keeps losing power. This requires explaining the dual safety mechanism of the power source. Essentially, the battery is a power storage station, providing a strong current of 500 amps to the starter during ignition. Once the engine starts, the crankshaft pulley drives the generator rotor to rotate, generating 14V DC electricity through electromagnetic induction. At this point, all vehicle electronics rely on it, and the higher the engine speed, the greater the power generation. The generator has an intelligent regulator that automatically reduces the charging current when the battery is full to avoid overcharging and bulging. However, if the generator belt breaks, even a fully charged battery won't last more than half an hour.

[MacVivian]

I remember being constantly worried about running out of power when I first started driving, until I learned that a car's electricity comes from both active and passive sources. When parked, all power comes from the big battery (usually 12V DC). But once the engine starts, the alternator connected to the front cover becomes the main power source - it converts about 30% of the internal combustion engine's energy into electricity. However, be cautious about opening windows in rain as water can short-circuit the alternator. My friend's off-roader had its alternator burnt after water crossing, causing complete instrument cluster failure requiring a tow truck. Regularly check battery terminals for oxidation, as poor contact leads to unstable vehicle voltage.