What is the normal power generation output of a car alternator?
3 Answers
The normal power generation output of a car alternator is 13.5V-14.5V. Here is some relevant information about alternators: 1. Classification of alternators: Automotive alternators can be divided into DC generators and AC alternators. Since AC alternators outperform DC generators in many aspects, DC generators have been phased out. 2. Symptoms of alternator failure: Dimming of headlights or dashboard lights; Damage to the battery or accumulator. If the battery is undercharged or dead, the vehicle will continue to run, but after a short time, the lights will dim again, indicating an issue with the charging system; The car alternator belt, if it does not rotate freely, excessive friction will cause the belt to heat up, producing a burning rubber smell. If you detect a smell similar to an electrical fire, this may indicate that the alternator pulley is slipping on the belt, resulting in poor alternator output.
Having run an auto repair shop for over a decade, I often encounter car owners asking about charging system issues. For normal vehicles after starting, measuring across the battery terminals with a multimeter should show 13.8 to 14.5 volts for optimal operation. In summer with AC running, spikes to 14.7 volts are common, but anything exceeding 15 volts warrants caution - the voltage regulator might be failing and "boiling" the battery electrolyte! Loose belts can drop charging voltage below 13 volts, with flickering headlights serving as warning signs. Start-stop equipped vehicles are particularly sensitive; unstable charging can strand you immediately - just last week a Mercedes S-Class fell victim to this very issue.
When working on classic car modifications, I found that power generation depends on the vehicle's era. The old Santana idles at 12.9 volts which is acceptable, but new energy EVs' charging modules require maintaining above 14.2 volts. If the voltage drops to 13 volts when headlights are on, it's time to check the carbon brushes. Last time when I modified my Jimny with additional spotlights, I noticed the voltage dropped to 12.7 volts while revving in neutral - turned out two diodes in the rectifier bridge were burnt. I recommend installing a cigarette lighter voltmeter, it's far more accurate than the onboard computer.
