How to control/activate regenerative braking?

I attend Ucsc and am currently working on my senior design project with five other engineers. We are building an electric bike and I purchased the Crystalyte 404 rear 16" hub motor. We are going to have a trailer attatched to the back of the bike to function as an electric push trailer. We want to include regenerative braking and run tests to see how effectively it will recharge the battery. To activate regenerative braking, we were going to use the motor acting as a generator. We are using the Allegro A3930 controller http://www.allegromicro.com/en/Products/Part_Numbers/3930/index.asp. How would we have regenerative braking? I know that current will flow from the battery through the controller into the motor. For Regeneration, will the current flow from the motor, through the controller to the battery? Will I need to add any circuity for this current to go through, as to have a current limit or a capacitor? I know that regeneration generates low numbers, and the battery may not retain extreemly small voltages? Would I need a capacitor somewhere to charge first, then use that to charge the battery? Please Help me :(!