An Experimental Study on Fire Suppression Devices for Power Batteries of Hybrid Electric Multiple Units

The hybrid type electric multiple units (EMUs) are generally equipped with LiCoO₂/Li₄Ti₅O₁₂ lithium-titanate (LTO) batteries. LTO batteries are often in a state of high-rate charging and discharging since they are mainly used for emergency traction and braking recycling of EMUs. Under such operating conditions, LTO batteries have a higher risk of thermal runaway, which would induce battery fires in the operation and lead to grave consequences. In this paper, a fire suppression device containing a fire detection tube was proposed for the power battery system of hybrid EMUs. Meanwhile, experiments were conducted to detect thermal runaway of the single battery and thermal expansion of the battery module installed with the fire suppression device. The fire detection tube was filled with clean agent Dodecafluoro-2-methylpentan-3-one. During the experiment, when triggering the process of thermal runaway, the fire suppression device prevented the battery from catching on fire successfully. Moreover, the fire suppression device had good cooling performance. The thermal runaway temperature of the battery with the fire suppression device installed was lowered to 130°C or so, compared with 550°C of the single battery alone. The fire suppression device was then installed in the battery system of a hybrid EMU, which performed well in operation.