I'm not a fan of regen personally, but I got to thinking about this the other day and couldn't figure out a reason why it wouldn't work.
Take your average DC series wound driven EV, but ensure it has a dual-shaft motor. One shaft goes to the transmission as usual, the other goes to an AC motor. While driving, the AC motor is not electrically connected to anything, so there's no load on it as a generator. You've got some efficiency losses due to weight and friction/heat but not much.
When breaking, connect the AC motor to a charger that charges the batteries. Now there is a load on the motor, and it should slow the DC motor. This doesn't seem that complicated to engineer, except possibly space limitations. Is there a good reason this would not work?
Take your average DC series wound driven EV, but ensure it has a dual-shaft motor. One shaft goes to the transmission as usual, the other goes to an AC motor. While driving, the AC motor is not electrically connected to anything, so there's no load on it as a generator. You've got some efficiency losses due to weight and friction/heat but not much.
When breaking, connect the AC motor to a charger that charges the batteries. Now there is a load on the motor, and it should slow the DC motor. This doesn't seem that complicated to engineer, except possibly space limitations. Is there a good reason this would not work?