Regenerative braking has been around for a while and can be a quite complicated system. All "regen" golf carts use a separately excited (sep-ex) motor. This means that the field winding and the armature winding inside the motor are powered and controlled independently. This allows for much greater control of the motor's performance characteristics. Regenerative braking is essentially an electronic governor that applies excess voltage, produced by the motor while coasting, back into the batteries. Thus the term "regenerative" (recharging). The inregen electronic speed controller usually limits the golf cart to a predetermined downhill, or freewheeling, speed. Once you hit this speed, the cart maintains that speed without the use of your foot brake. The speed limiting capability is one of the most useful applications of regen systems, but the charging efficiency is pretty low.
This resistor is used in Club Car Golf Cart regen systems to burn off (displace) excess voltage generated when the batteries are fully charged and cannot accept anymore regen voltage. If you freewheel down a hill on a fully charged set of batteries, where does the regen energy go? Until the batteries lose a bit of their charge, this resistor displaces that energy as heat into the atmosphere. Once the batteries lose a little charge, this resistor coil is bypassed and the excess residual voltage from the regen process is then allowed to flow to the batteries.
Now if you Google Club Car energy displacement module you will get a picture of the solenoid with that coil attached and it is not used for reverse.