Is a PWM required for regenerative braking on a DC Motor?
(Assuming that the voltage from the motor when braking exceeds the motor power)


That's the problem &mdash; it doesn't. You need a way to boost the voltage coming from the motor to a level that will actually charge the battery. You can use a separate boost converter, or you can create a more tightly integrated solution that uses the inductance of the motor itself as an element in a boost converter. Either way, it does involve some sort of PWM control in order to regulate the power flow.