[NiHaoMike]

You use a PWM controller to switch a MOSFET. In your case, the motor acts as the inductor, so you just need to add a diode across the motor and a bypass cap on the input. Have the PWM controller try to hold the input voltage at the MPPT spec and it should work great. I suggest using a slow response (10Hz bandwidth or so) as that helps keep it stable. A good switching frequency to use is about 4kHz if audible noise is not an issue, 20kHz if it is.