At what voltage can a car battery no longer start the engine?
2 Answers
When the open-circuit voltage of a car battery drops below 12.2V and the load voltage falls below 9.5V, it can no longer start the engine. The functions of a car battery are as follows: 1. During engine startup, the battery supplies power to the starting system, ignition system, and electronic fuel injection system; 2. When the engine is off or idling, it powers the vehicle's electrical equipment; 3. It can assist in powering electrical devices when the alternator's output is insufficient; 4. It mitigates voltage surges in the electrical system, protecting the vehicle's electronic components; 5. It stores excess electricity generated by the alternator. Charging precautions for car batteries: 1. Always connect the battery directly for charging; avoid removing it to prevent data loss; 2. If the battery voltage is 10% below the rated voltage, it may lead to battery depletion; 3. Avoid exposing the battery to water during charging.
I've been driving sedans for over a decade, and when the battery voltage drops below 11.8 volts, the car usually won't start. I remember one winter when my car sat idle for a long time, the voltage showed 11.7 volts. Turning the key only produced a clicking sound, and the car wouldn't budge, forcing me to ask a friend for a jump start. A fully charged battery should read 12.6 volts, and starting the engine requires a significant current. If the voltage is too low, there won't be enough current supply. Cold weather makes it even more sensitive; below freezing, the battery might fail at 12.2 volts. I recommend using a multimeter to check the voltage every season, keeping it above 12.4 volts. Take more long drives to charge the battery and avoid using electrical appliances when the engine is off to prolong battery life. If the voltage consistently hovers around 12 volts, it's time to prepare for a replacement—don't wait until you're stranded to act.
