How does the current change?
The current of the motor is not a fixed value, but varies with the working state:
No load current: The motor consumes the minimum current when idling, used to overcome its own friction.
Rated/load current: The normal current of the motor when operating under load as required, usually indicated on the motor nameplate or instruction manual.
Starting/stalling current: The current at the moment of motor starting or when the shaft is stuck and stalling, usually 4-7 times the load current.
This is the peak of current consumption, which may be very large.
The current of a 12V DC motor depends on power, load, and efficiency, with a rough range of:
1、 Common current range (12V)
Micro motors (N20/370, etc.)
No load: 15-100 mA
Rated: 0.1-1 A
Stuck (stuck): 2-5 A (≈ rated × 5-10 times)
Small reduction motor (37GB/520, etc.)
No load: 50-150 mA
Rated: 0.5-3 A
Blocked rotor: 3-10 A
Medium/high power (car/water pump/tool)
Rated: 5-20 A
Locked rotor: 20-100 A (short-term)
No load: 50-150 mA
Rated: 0.5-3 A
Blocked rotor: 3-10 A
Medium/high power (car/water pump/tool)
Rated: 5-20 A
Locked rotor: 20-100 A (short-term)
2、 Simple calculation formula
Rated current: I ≈ P ÷ 12 (P=power W)
Example: 60W → 60 ÷ 12=5A (rated)
Considering efficiency: I=P ÷ (12 × η), η ≈ 0.7-0.9
Rated current: I ≈ P ÷ 12 (P=power W)
Example: 60W → 60 ÷ 12=5A (rated)
Considering efficiency: I=P ÷ (12 × η), η ≈ 0.7-0.9
3、 Practical reference (12V)
Toy/Mini Motor: 0.1-0.5 A
Car/robot motor: 0.5-2 A
Water pump/fan: 1-5 A
Window/wiper motor: 5-15 A
Start/stall: rated × 5-10 times (must leave margin)
Toy/Mini Motor: 0.1-0.5 A
Car/robot motor: 0.5-2 A
Water pump/fan: 1-5 A
Window/wiper motor: 5-15 A
Start/stall: rated × 5-10 times (must leave margin)

