The performance of a battery–electrical double layer capacitor (EDLC) hybrid power source at low ambient temperature has been experimentally analyzed. EDLC can enhance the performance of lead-acid battery as it acts as a buffer during charging and discharging, and plays more significant role at low temperature than room temperature. The behaviors of current and voltage of both battery and EDLC have been detailed studied, and described by a mathematical model. With EDLC assistance, the battery can maintain longer discharge duration at −25 and −10 °C, compared with the battery alone. Adding an EDLC in parallel with the battery exhibits a considerable capacity increase compared to battery standalone in continuous discharge processes: from 13.6 to 36.5 %, corresponding to 25 to 200 A. These improvements of capacity become even more significant at low temperature. The increases in available capacity of different pulse duty, amounted to 72, 58, and 4 % at 0.1, 0.5, and 0.9 duty cycle values, compared to the capacity measured at constant current rate, respectively (calculated by 50 A discharge).
