Thanks both of you for the clarification,
I think now I see resistors are more of a way to split amps on a wire to a few different sources at the same time. For a single battery > motor wire with no other paths, it is better to forget the resistor and use a coil charged by the motor, and then use a redstone signal to both turn off the motor and start using the coil when it is at suitable capacity. With the way things appear to be designed, this seems to make more sense.
I think now I see resistors are more of a way to split amps on a wire to a few different sources at the same time. For a single battery > motor wire with no other paths, it is better to forget the resistor and use a coil charged by the motor, and then use a redstone signal to both turn off the motor and start using the coil when it is at suitable capacity. With the way things appear to be designed, this seems to make more sense.