car' s alternator

 A car's alternator must take in order to give.

This means that it needs electrical voltage to operate its rotor coil, which produces 12 volts or more with high amperage while the engine is rotating.

 This is because the alternator contains two coils:

The rotor coil requires 12 volts from the battery to become a magnet.

The other coil is fixed, producing 12 volts or more with high amperage. 

This is what we rely on for the alternator's output and battery charging.

The car battery is an alternative to the smoothing capacitor and performs its role.

However, if we use the alternator outside the car to generate electricity, as shown in the picture, by supplying it with rotational motion from some source other than the car's engine,

it must be supplied with temporary power, alternative to the car battery, so that it can produce power from the fixed coil, while also supplying it with a large-capacity C1 capacitor to smooth the current.