Patent ID: 9071069
Filing Date: 2015-06-30
Classification: B25F,G01R,H01H,H01M,H01R,H02J,H02P,H05B,Y02E,Y02P

Abstract:
1. A method for operating a power tool having a motor powered by a battery pack, comprising: setting the duty cycle of a pulse width modulated control signal in accordance with a position of the trigger switch; delivering power from the battery pack to the motor in accordance with the control signal, the battery pack having a positive terminal, a negative terminal, and a temperature sense terminal, the battery pack housing a battery coupled to the positive and negative terminals and a temperature sensor arranged between the positive terminal and the temperature sense terminal; monitoring a temperature of battery pack using a signal received from the temperature sensor via the temperature sense terminal; and fading the power delivered from the battery to the motor when the temperature exceeds a temperature fade threshold, through the use of a controller residing in the power tool, wherein the fading step comprises: computing a value of the duty cycle as a function of a value of the temperature, and setting the duty cycle of the control signal to the computed value of the duty cycle when the computed value of the duty cycle is less than the duty cycle set in accordance with position of the trigger switch, and retaining the duty cycle set in accordance with the position of the trigger switch when the computed value of the duty cycle is more than the duty cycle set in accordance with the position of the trigger switch.