A 12V generator cannot charge a 12V battery, and it cannot charge much. It is recommended to use 16V. Generally, when charging two 12V batteries in series used on a large vehicle, a 28V generator is used. Go to those places that specialize in generators and ask them. Wind-powered ones are quite rare in our area.
Use a 9V-12V toy DC motor, plus a wind propeller (actually a brushed DC fan), and in turn use it as a wind DC generator.
Connect the two electrodes of the motor to a bridge rectifier (avoid reverse connection of positive and negative), and connect the output to a 5.6V Zener diode and a 1000mfd/10WV electrolytic capacitor. This way you can charge the power bank.
For safety reasons, a 1000 microhenry 1A inductor can be connected in series to the output end to prevent surges from damaging the power bank chip.
It’s good to do an experiment. Unless the wind is strong, the charging effect may not be ideal.