Current-Compensated Discharge Limiter for Industrial Battery-Powered Vehicle

Battery-Powered vehicles require that drivable range be maximized. This requirement is at odds with the need to protect the battery from over charge and over discharge. This is especially true when the electric vehicle operator is not sufficiently knowledgeable about battery operation. Several technologies were examined to prevent excessive discharge during operation of a luggage tractor. None of the existing technologies were found to be appropriate for this application. A new scheme was developed whereby battery terminal voltage is compensated by discharge current. By carefully selecting the control curve relative to the internal resistance of the battery, discharge energy output is maximized while still providing protection against excessive discharge. A device was developed using this new scheme. The device was developed as an external interface with a specific motor controller and used the accelerator command signal to limit power drawn from the battery as the means of discharge control. Vehicle testing with the discharge-limiting device showed that the new scheme allows for sufficient energy output from the battery while providing gradually increasing power limitation to protect the battery.