A monitoring system for a multi-cell rechargeable energy storage system (RESS) that includes a plurality of battery cells is described. The monitoring system includes a sensor that is arranged to monitor one or multiple heat transfer plates thermally coupled to the plurality of battery cells, a controller is in communication with the sensor. The controller including an instruction set that is executable to monitor, via the sensor, a parameter of the heat transfer plate and detect a thermal runaway event when the parameter of the heat transfer plate exceeds a threshold. The thermal runaway event is communicated to a battery controller.