An energy storage system comprising at least one energy storage module adapted to supply electrical energy to a hybrid vehicle. The energy storage module comprises an enclosure, at least one battery array located within the enclosure, and an energy storage controller module located within the enclosure and electrically connected to the battery array. The energy storage module further comprises a compliant tipped thermistor which may be installed within a flexible clip. The thermistor is positioned to monitor the temperature of one or more of the batteries within the energy storage system.
