How long does it take to charge a dead car battery at idle speed?

[FrankFitz]

The charging time for a dead battery at idle speed is as follows: 1. If the engine speed is 1500 rpm, charging for 20 minutes can provide enough power to start the engine once. 2. Charging at 1500 rpm for 30 minutes can provide enough power for one start the next day. 3. If charging at 1500 rpm for more than 60 minutes, the battery can be fully charged. 3. It is best to charge while driving rather than at idle speed, as prolonged idling can cause engine wear. Below are some points to note about avoiding charging a dead battery while stationary: 1. Prolonged idling can lead to carbon buildup in the engine combustion chamber. 2. Stationary charging is not ideal, as the generator produces very weak power at low speeds. Only during normal driving will the generator's current reach the designed standard. 3. For safety reasons, idling a car produces exhaust fumes, which can be toxic in an unventilated environment, posing a significant risk of accidents. 4. If the generator is faulty, stationary charging will not work, and the solution is to drive to a repair shop for inspection.