How long can the car be turned off after jump-starting when the battery is dead?
3 Answers
After jump-starting a car with a dead battery, it should run for more than 1 hour before being turned off. Ensure all electrical devices are switched off before turning off the engine. Here are some methods for car battery maintenance: 1. Turn off lights and audio systems before parking and shutting down the engine; 2. Avoid leaving the air conditioning on when turning off the engine; 3. Drive the car periodically for a certain distance; 4. Regularly clean the battery; 5. Prevent battery discharge; 6. Check the battery every six months; 7. Monitor the battery status indicator promptly. Additional information: If a car battery is left unused for a long time, it will gradually self-discharge and eventually become unusable. Therefore, the car should be started periodically to recharge the battery.
Last time my car battery was dead, after a friend helped jump-start it, the mechanic told me I needed to drive for at least twenty minutes before turning off the engine. He said the alternator only starts charging when the engine is running, and turning it off immediately would be like not charging at all. That time, I drove slowly in the city for half an hour, deliberately revving the engine to increase the charging efficiency. Now, every time I encounter such a jump-start situation, I drive an extra five kilometers, especially since winter or an old battery requires more charging time. Before turning off the engine, it's best to turn off power-consuming devices like the air conditioning and headlights to ensure the next startup.
As someone who has worked in a repair shop for several years, I think this issue depends on the specific situation. After jump-starting, the alternator starts working, but you need to let the engine run for at least fifteen minutes to store enough power for the next start. If the battery is three or four years old, I recommend driving for thirty minutes to be safer. It's better not to just idle in place; driving at around 2,000 rpm doubles the charging speed. Remember to check if the alternator belt makes any unusual noises—if it's loose, the charging efficiency drops. If the car can't start again after turning it off, it's likely that the battery is failing and needs replacement.
