What is the starting current of a motorcycle?
2 Answers
Under rated load, the working current can range from 40-50 amperes for smaller models to over 100 amperes for larger ones, with the motor's braking current potentially reaching 100-250 amperes. Introduction to Starting Current: The starting current of a motor refers to the line current input when the motor is connected to the rated voltage and begins to start from zero speed. The starting current of a motor is generally 5 to 7 times its rated current. A motor's excessively high starting current can significantly impact electrical equipment and the power grid. Principle of Starting Current: At the instant the motor is energized and remains stationary, the rotor is motionless with a speed of 0. The synchronous rotating magnetic field then cuts the rotor windings at maximum speed, inducing the highest electromotive force in the rotor windings and generating a very large current. This current counteracts the magnetic flux of the stator field, prompting the stator windings to automatically increase current to maintain the original magnetic flux compatible with the power supply voltage. Since the rotor current is very large at this point, the stator current of the motor also increases significantly, reaching 5 to 7 times the rated current. This is the reason for the high starting current in motors.
Back when I rode motorcycles, I was particularly curious about starting current and even went to a repair shop to measure it with a meter. My 250cc street bike had a starting current of around 100 amps, and it could reach up to 120 amps in winter. Actually, there's quite a difference based on engine displacement—a 125cc scooter typically draws about 50-70 amps, while bikes over 600cc easily exceed 150 amps. Starting current mainly depends on the motor's power and compression ratio; modified engines can see a surge in current. The key is to match the battery's CCA (Cold Cranking Amps) rating, which indicates its cold-weather starting capability. If the battery's CCA is insufficient, the voltage drops sharply during ignition, and the battery will wear out quickly after repeated attempts. Later, when I replaced my battery, I always chose one with a CCA rating 20% higher than the factory specification, and I never had starting issues again.
