While it would technically be possible to add a dynamo to a hybrid vehicle in order to generate additional electricity, the result would actually be a net loss of energy. The dynamo itself would create additional rolling resistance which would then use extra energy from the engine or electric motor to power the vehicle to the same speed. It would also require a dynamo of significant size in order to generate any meaningful energy, so the drag created would be significant. There is also the fact that no energy transfer can be made without a degree of loss, so a proportion of any energy generated would be lost to heat and electrical resistance.

The result would be a vehicle that uses more fuel and electrical energy than an identical one not fitted with a dynamo. The current system of harvesting energy when braking makes sense because it utilises the vehicle's kinetic energy which would otherwise be lost to heat through the brake pads and discs.