1. A method of estimating a temperature of a battery system, the method comprising: receiving battery system temperature measurement data from one or more first temperature sensors associated with the battery system; receiving ambient temperature measurement data associated with an ambient temperature proximate to the battery system from one or more second sensors associated with the battery system; and determining an average estimated temperature of the battery system using, at least in part, an extended Kalman filter based on the battery system temperature measurement data, the ambient temperature measurement data, an energy balance process model associated with the battery system, and a temperature parameter.