Hi, First time post here. I found your article on regen braking very interesting but incomplete as you didn't explain how the current flows worked to recharge the battery. Essentially, regen braking works by shorting out the windings of the motor according to whichever one of the 3 bottom mosfets is turned on at the time and goes through near as dammit 1 &1/2 windings currents worth at any one time. This is actually quite power inefficent and just heats up your motor and can cause internal heat build up and can seize your motor at some point. especially if overvolting. ( W= VI).
The answer is actually very simple and occurs when no pulses at all go to any of the mosfets in the 3 phase bridge. This situation is true and applies to both controllers with and without regen braking but no freewheel and is actually a good simple test of whether your motor has a freewheel or not and works like this all the time, regardless of whether you've got a regen controller or not.
Remove the battery and connect a voltmeter to the battery leads from the controller or turn the lights on if they are inbuilt.
If you get a voltage or your lights start to work then your motor and controller is acting like a permanent magnet 3 phase alternator, like the one in a car. The reason for this is that with no pulses going to the mosfets, they are turned off and all that matters is the built in protection diodes. With every phase change, alternate higher and lower opposite pairs of diodes will conduct and store power in the controller's capacitor. When the voltage gets high enough, it will transfer current back to the battery if there is no blocking diode in the BMS. However, your battery will not recharge unless your wheel is spinning at a high enough RPM to overcome the voltage of your battery. Quite fast most of the time.
If you really want to recharge your battery at a lower RPM or dump the power back into your battery when braking or going downhill, then what you have to do duplicate the 6 protection diodes circuit with the input going from the 3 phase wires and the output to a capacitor and a DC-DC step up convertor with an protection bypass diode for when the generator voltage is high enough on its own to charge the battery, and can be controlled via semiconductor switches or relays via your throttle or pedelec or brake voltages or a simple switch and/or in conjunction with your regen braking system or preferably not.
Obviously not for everyone but If you are really serious about getting as much mileage as possible out of your battery, then this is a better way to go, as it dumps any surplus kinetic energy into your battery rather than your motor and may prevent it seizing up. Sealed hub motors with built in controllers seem to be prone to heat build up if operated out of spec or in the rain from what I've read.
What else are external disc brakes for except to dissipate heat as rapidly as possible while slowing you down as quickly as possible?
Here's a link to EE Times - understanding regeneration part 2 and has got some diagrams of how the current flow works when the motor is being used as a generator with mosfets.http://www.eetimes.com/document.asp?doc_id=1274137
I hope I've given a few people some ideas - Cheers!