An energy storage device for use with an electric vehicle includes an electrical energy storage device configured to be coupled to an electrical traction system of the electric vehicle to provide electrical power to the electrical traction system. The energy storage device also includes a sensor integrally mounted within the electrical energy storage device and configured to measure a voltage of the electrical energy storage device. The sensor also includes a status indicator integrally mounted to the electrical energy storage device and configured to provide a visual indication of the voltage.