Electric motor controllers that dynamically adjust a motor resistance parameter are described. In order to adjust the motor resistance parameter, power is applied the electric motor while the controlled vehicle is stopped and its brake is set so that the vehicle remains stopped while a measurement is taken that can be used to determine motor resistance. A new motor resistance value is then generated based at least in part upon the measurement(s) and the motor resistance parameter is set to the new motor resistance value. The new motor resistance parameter may then be used in the control of the electric motor. In some embodiments, the measurements are taken after the controller receives a brake release request but before actually releasing the brake. The described arrangement can be used in a wide variety of motor controllers and is especially well suited for use in low cost controllers that control motors that are susceptible to wide variations in their resistance such as brushed permanent magnet DC motors.