I have read that locomotives use eddy current braking systems, and one article mentioned that this system has also been used to charge batteries in a recovery circuit. However, I can not find details on this idea. From what I understand, the train has conducting discs attached to the wheels, and an electromagnet is charged in close proximity to the disc producing a powerful torque via the eddy currents produced in the disc. How could a system recover electric current from this disc, I thought most if not all the force is converted to heat in the disc. Anyone have any ideas?