A Simple Regenerative Braking System That Can Boost Upto 36V and Works on BLDC Motor.

Regenerative braking is a mechanism that recovers the kinetic energy by slowing down the vehicle and store the energy in any form i.e., mechanically, electrically, chemically or by using a pressure vessel. It improves the overall efficiency of the vehicle. In the time of regenerative braking, the motor acts as a generator while moved by hand or while the drive axle rotates the motor when the vehicle is coasting due to the production of Back electromotive force. Its magnitude is always lower than the supply voltage. As the permanent magnet rotor is driven by the drive axle, the magnetic flux cuts the 3 windings of the stator coil, generating AC voltage which varies depending on speed. The AC voltage is rectified and then purified with a capacitor bank. The Voltage is lower than the battery voltage, so to charge the battery power electronics like a boost converter is required.

Advantages-

1. One pedal driving

2. Enhanced overall efficiency

3. Longer lifespan of the braking system as the wear and tear are minimized.

Limitations-

1. Can’t stop the car completely

2. Can’t immobilize the vehicle, a parking brake is required.

3. Only applicable to the wheels having a motor connection. If 2WD, only 2 wheels will get regenerative braking.

Supplies

Autodesk Eagle or Proteus
N4007 6A diode
Boost converter (200 W) 1 piece
Capacitor 35v 2200 microfarad 4 pc
Regen indicator 1 pcs
Connectors for Battery. 1 pc
zener diode of 40v and fuse 2 pcs
brake pedal switch 1 pcs
Reverse switch 1 pcs
verro board and box 1 pcs
Workhour (20H)

Step 1: Bit of Theory

in this circuit, we will be using it to regenerate electricity from the Back EMF of a BLDC motor. A BLDC motor uses an inverter to make AC input which is fed into the 3 phase of the BLDC motor. When the driver doesn't give any input and vehicle is rolling, the magnetic field of the permanent magnet cuts through the field coil and generates the back EMF( which is directly proportional of motor speed and strength of magnetic field). if this EMF is not captured, the motor rotates freely, but when you try to capture the Back EMF, the motor speed decreases and the desired braking effect occurs. Modern motor controllers already have bidirectional capability where it can do both the functions. But this instructable are for those who has single way inverter that does not fed back emf back to the battery.

Step 2: Understanding the Circuit

In the circuit, the motor is depicted as AC source, a rectifier circuit is given to rectify the AC voltage into pulsating DC. A capacitor bank to smoothen the ripples . As the voltage is very low, and you need to step up to feed a 36V battery, ( actually I couldn't find 48V boost converter to feed our 48V battery, if you find, you can use) you have to use the boost converter, its main task is to step up the DC low voltage to DC high voltage. There is a screw to turn, you can check the voltage output from the DC boost converter. At last put the zenner diode in reverse to protect your battery from over voltage spikes ( zener diode will not pass more than 40V to battery, thus protecting it.) For extra protection, you can add a kill switch and a fuse of appropriate ampere.

Step 3: Build It

Just get the verro board, connect it according to the given circuit diagram, and make the H bridge of rectifiers, you'll have less space up, so take the main +ve and -ve connection to the battery from the other side of the verro board. The circuit can be used in two ways, one is when you don't use the accelerate pedal, the regen module is automatically activated. another mode is when you press the brake pedal, the regen module is activated. (if this mode you want, make sure you have the brake switch connected with a relay that activates or deactivates the controller power wire.) That's it, you own your own regenerative braking module. Tweak the screw of the boost converter( aka chopper) using the multimeter to see the voltage output and set accordingly.