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There is a very clear regulation in the old national standard of electric bikes: electric bikes should have a brake power-off device, which should be able to automatically cut off the power supply when braking. That is, when braking, the controller detects the braking signal and no matter what the state of the speed control lever is, the power supply of the motor must be disconnected, so as to realize the function of braking power-off.
In the past, the electric brake pads made relatively small. The contact area was small and the brakes did not work well. Many electric vehicles were replaced with new brake pads, which were not very sensitive. When stopped, the brakes felt very responsive. But when riding, they didn't work at all and the brakes were very hard. This is a common problem with the earliest electric vehicles.
Let's take the most common two-wire mechanical brake lever as an example. The brake switch has two wires. One black wire is connected to the 12V power supply and the other yellow-green wire is connected to the brake power off signal. That is, the power is input from the black wire, the brake switch is turned on. And the yellow-green wire is the output wire, which is also 12V voltage. In the case of not braking, the switch is in the closed state. When in the braking state, the switch is turned on to provide 12V voltage for the tail light and input voltage to the relevant input terminal of the controller at the same time. When the controller receives the signal voltage, the power supply to the motor is cut off. The input power wire has a voltage of 12V all the time. The voltage between the yellow-green wire and the negative electrode is either OV when the switch is off, or 12V when braking and the switch is on. Because the wires of the front and rear brake switches are connected, as long as any electric bike brake is grasped, the front brake and the rear brake can achieve the purpose of braking power off.
The other type is the normally open switch. When not braking, the voltage of the power-off signal wire is 12V. The power-off signal is OV when braking. This switch is mostly used on simple electric vehicles without converters and most of these vehicles do not have brake lights.
The brake switch is just a small part and just worth a little money, but it does a lot and is very important. Therefore, when there is a problem with the electric bike brake, it should be replaced in time. Do not try to remove the brake switch cable easily. Even if there is no brake light, the brake power-off function should be retained.