A power tool is provided including: a housing including a battery receiving portion configured to receive a removeable power tool battery pack and a motor housing; a brushless direct-current (BLDC) motor disposed within the motor housing, the motor including a stator and a rotor; a power switch circuit disposed between the battery receiving portion and the motor; and a controller that controls a switching operation of the power switch circuit to regulate a supply of power from the battery pack to the motor. At tool start-up, the applies a series of voltage pulses to the motor and measures a corresponding series of motor phase current values to identify an initial position of the rotor relative to the stator. Further, the controller identifies at least one of an impedance or a capacity of the battery pack as a function of the motor phase current values.