The circuit is shown in the figure. Since the AC output voltage of the three-phase generator is 1.8VRMs, a double voltage rectifier circuit is used to increase the output voltage, and the diode uses a Schottky diode with a low forward voltage drop. The charging object is two nickel-cadmium or nickel-metal hydride batteries, which are 1.4Vx2=2.8V when fully charged. The forward voltage drop of the anti-reverse current diode is 0.3V, which is 3.1V in total, so 3.1V constant voltage charging is used.

IC1 is a DC-DC conversion chip 1T1173. The output voltages of the three voltage-doubling rectifier circuits are connected in series and input to the Vin terminal of IC1. When the voltage of the feedback terminal FB is lower than 1.245V, the internal 24kHz oscillator of IC1 starts to oscillate, and the voltage of its output terminal SW2 increases. After the voltage is divided by R1 and R2, the voltage of the FB terminal also increases. When it increases to 1.245V, the internal oscillator stops oscillating, causing the output voltage to drop. This process is repeated to obtain a constant voltage output.

 

In the figure, R1 and R2 are error voltage detection resistors. Output voltage Vout = (1 + R2/R1) × 1.245V = (1 + 15k/10k) × 1.245V = 3.1V; R6 is the current detection resistor on the power generation side.

R4 is the charging current detection resistor. The voltage drop on the resistor can be measured with a digital voltmeter and converted into a current value. R3 is the current limiting resistor of the internal switch tube of IC1. R5 is the charging current limiting resistor:

D7 is used to prevent the reverse voltage of 11 from affecting the SW2 terminal of IC1; D8 is a reverse current protection diode.
The actual charging result is that after charging for 14 hours, the charging capacity reaches 600mAh and the discharge capacity reaches 525mAh, which means 90% of the charging capacity can be used.

When the wind speed is 1m/s, the blades start to rotate and charging begins, with a current of about 40mA; when the battery is almost fully charged, the charging current decreases, so long-term charging will not damage the battery; and in strong winds, the battery will not heat up. The wind power generation device introduced above has reached the practical level, but increasing the number of generators or selecting a generator with a higher power can expand its application range.