Techniques and circuitry, in one embodiment, determine a temperature of a battery by applying a calibration packet to the battery's terminals and at the battery's first SOC, wherein the calibration packet includes a first pulse (charge or discharge) which temporally precedes a rest period. In one embodiment, measurement circuitry measures a first terminal voltage at a time immediately prior to or at a beginning of the first pulse of the calibration packet, and a second terminal voltage, in response to the calibration packet, at a time during the partial relaxation time period of a battery. Control circuitry determines a partial relaxation time voltage (VPRT) at the battery's first SOC using the first and second terminal voltages and determines a temperature of the battery by correlating the VPRT at the first SOC to a temperature of the battery at the battery's current SOH.