How Much Current is Needed for Car Ignition?
2 Answers
Generally, the starting current of a passenger car ranges between 100 to 300 amperes. If the engine has a larger displacement, the starting current will increase accordingly. Different engines are equipped with different starters, and the power of a car starter typically ranges between 1 kilowatt to 3 kilowatts. Below is the principle of starting current: 1. At the moment the motor is energized, when the motor is in a stationary state, the rotor is motionless, and the rotor speed is 0. The synchronous rotating magnetic field cuts the rotor windings at the maximum speed, inducing the highest electromotive force in the rotor windings and generating a large current in the rotor windings. This current will counteract the magnetic flux of the stator field. To maintain the original magnetic flux compatible with the power supply voltage, the stator windings will automatically increase the current. Since the rotor current is very large at this time, the stator current of the motor will also increase significantly, up to 5 to 7 times the rated current. 2. As the motor speed gradually increases, the speed at which the stator's synchronous rotating magnetic field cuts the rotor windings gradually decreases, the induced electromotive force in the rotor windings gradually decreases, and the current in the rotor windings also gradually decreases. Consequently, the current in the rotor windings that counteracts the stator field's magnetic flux maintenance also decreases. Finally, when the motor reaches the rated speed, the current in the stator windings decreases from large to small and eventually returns to the motor's rated current.
I've been repairing cars for over 20 years, and I've seen plenty about starting current. For regular cars, the instantaneous current during ignition typically ranges between 100 to 200 amps. In winter or with an old battery, it can surge above 300 amps. The starter requires high current to instantly rotate the engine and provide sufficient torque to overcome compression. Remember, the battery's CCA (Cold Cranking Amps) value is crucial—it should be at least 500 to be reliable. Always check that the battery terminals are clean to avoid corrosion or looseness, which can affect current conduction. If you're having trouble starting, don't force it—test the battery voltage and starting current. For example, SUVs often require around 300 amps. From my experience, high-current-demand vehicles like pickup trucks need their batteries replaced more frequently to prevent breakdowns and ensure safe driving.
