Three phases from a micro wind turbine are rectified (the 1ohm resistors simulate the winding resistance).
The AC is converted to DC which is somewhat stabilized with a capacitor (100µF). Once the voltage from the rectifier exceeds the battery voltage, a current can flow into the battery. The +- 200 mOhm resistance is a simulated internal resistance of the battery.
It is desirable to limit the voltage at which the battery can be fully charged to optimize it's lifetime. In this case the limit is set at 14.5 volts and is controlled by a very simple comparator setup where the line voltage goes through a divider bridge and where this voltage is compared to a reference voltage created (in this case) by a 6V zener diode. This value can be anything under the minimal battery voltage but be carefull to also adjust the voltage divider or else this will no longer work.
Once the voltage reaches the max voltage, the divider voltage will surpass the reference voltage and the comparator will switch so that a positive voltage appears at the output. This in turn switches a (power) MOSFET that closes a circuit an allows current to flow from the battezr/generator to a dump load (1 Ohm resistor in the bottom right).
Many improvements can be made to this circuit but the basics seem to work here.
I am currently converting a 3 phase "hoverboard) motor to a wind turbine generator and hope to test this circuit out in combination with a lead-acid battery. I may update some values based on the live tests later on but for now I really like this little circuit.
Questions: How to better stabilize the reference voltage (zener)?
More accurate switching: Now the circuit also switching to allow dumping when the voltage is below the max charged voltage because of higher peak voltages. This causes a substantial ammount of energy to be dissipated through the dummy while it could still be used to charge the battery which is not yet at capacity. I realize, however, that this is actually desirable behaviour since it is better to 'trickle' charge when reaching the max charge. Nonetheless I would like to know how to have even more control without adding to complex components/circuitry
