How to convert electric vehicle hub motor into a generator

It is very simple to convert a hub motor into a generator, and it is OK to convert a low-voltage motor for fun. It is not suitable to be converted into an AC 220V generator. Because after this motor is converted into a generator, the output voltage is unstable, and the voltage increases with the increase of speed. External power is required to maintain a higher and stable speed to output 220V voltage. Therefore, it is more practical to convert it into a low-voltage wind turbine. With the help of a voltage stabilizing circuit to charge the battery, it can provide 220V AC after inversion, solving the problem of no city electricity in mountainous areas.

The brushless motor of an electric vehicle is a three-phase brushless permanent magnet motor. The basic principle is as follows:

The rotor is made of permanent magnetic material, which is the wheel hub and shell of the electric vehicle. The stator is composed of three sets of coils. The three sets of coils are connected in a star shape, connected at the tail, and three phase lines are led out of the three sets of coils. When used as an electric motor, the three sets of coils are input with DC voltage in sequence to form a rotating magnetic field. The motor rotor will rotate under the impetus of the rotating magnetic field. Because of the existence of the permanent magnetic rotor, this process is also reversible. As long as the rotor is rotated, current will be induced in the three coils of the stator. Therefore, the simplest modification method is to make no internal changes, and the three output wires can be directly rectified with six diodes to output DC power.

With the solar panel controller, the battery can be charged, and with the inverter, it can be used! However, such changes also have certain requirements on the motor speed. The lower the speed, the lower the output voltage. Therefore, if you want to reduce the speed and increase the power generation voltage, you need to make certain changes to the stator coil.

After disassembling the stator in the above picture, you can find three phase wires, which are led out by three thicker three-core wires. If you want to increase the output voltage, you must disassemble the coil connector and open the contacts at the end of the three sets of coils, so that the three sets of coils are completely independent! If the voltage increase is not much, just double it, then you can connect the three sets of coils in series, and finally output a single AC power. It can be rectified, or it can be used with a transformer to boost the voltage. The output is connected to the secondary of the transformer (thick wire), and the primary of the transformer can output high voltage (AC). If the voltage requirement is high and increased by N times, then the coil needs to be further modified.

After opening the coil connector, we will find that each coil is composed of N enameled wires connected in parallel, so we group all the enameled wires of each coil separately, for example, two as a group, and then use them in parallel. You can use a multimeter to find the wire ends and connect two enameled wires in parallel to form multiple groups.

After the coils are grouped, we can connect the grouped wire ends in series by connecting the ends together. In this way, the three groups of coils are divided into N groups of individual coils. After the N groups of individual coils are connected in series, the output voltage can be increased by N times. The whole DIY process is still quite troublesome. Different motors have different parameters and output voltages. It may take multiple changes to achieve a satisfactory effect. You can do a test before making changes. For example, test the output voltage of the motor at a specific speed. If it is not ideal, you can change the internal coil connection method according to the voltage to obtain the ideal output voltage.