A power supply temperature sensor and system includes a power supply housing configured to receive at least one power supply unit, such as a battery cell. The power supply housing includes an aperture which provides communication between the battery cell and an ambient environment outside the power supply housing. A sensor having a sensing element is configured to sense a temperature of the battery cell, and a sensor housing surrounds at least a portion of the sensor, including at least a portion of the sensing element. This electrically isolates the sensing element from the battery cell.; A portion of the sensor housing is configured to be disposed through the aperture in the power supply housing to make contact with the battery cell to facilitate conductive heat transfer between the battery cell and the sensor housing, thereby facilitating an accurate measurement of the temperature of the battery cell.