Control method for cooling fans inside traction battery boxes installed in battery powered EMU based on thermal network model

Recently, there has been a gradual increase in the use of battery powered electric multiple unit trains (EMUs), replacing the conventional diesel trains for nonelectrified lines of approximately 10–30 km. Battery powered EMUs are typically equipped with closed‐type traction battery boxes, in which cooling fans are mounted. To improve the performance of battery cooling, we developed a control method for the cooling fans. Our novel method is derived from a thermal network model of the battery box, and is based on the temperature difference between the battery modules and outside air. We conducted an evaluation test for the Series BEC819, an AC‐fed and battery‐powered hybrid EMU of JR Kyushu. The test results demonstrated that the developed control method reduced maximum temperature of the battery by 1–2°C in comparison with the conventional constant speed control.