4
respectively, and both were 25 °C at the thermal runaway
onset (Figure 6). No flame was observed from the cable
entrance.
The thermal runaway cascade proceeded rapidly
throughout the battery as indicated by temperature mea-
surements at several battery locations (Figure 7). A post-test
inspection confirmed that thermal runaway occurred in
all of the cells. Table 2 lists battery and enclosure inter-
nal atmosphere temperatures just before and at the peak
of thermal runaway. A higher temperature of 1097 °C was
measured outside of the enclosure (Figure 6). The 1097 °C
measurement is also higher than MH1 cell thermal run-
away temperatures measured within sealed enclosures [10].
Yuan et al. [14] found that the MH1 cell (identified as
NMC 2) thermal runaway produced significant amounts
of inert carbon dioxide gas and flammable gasses including
hydrogen, carbon monoxide, methane, and lesser amounts
of a few heavier hydrocarbons. MH1 cell thermal runaway
produces about 0.66 liters of gas per watt hour of battery
energy [10], corresponding to 283 liters of gas generated by
the 429 Wh battery pack. Gas generation from the battery
should displace atmospheric oxygen from the XP enclo-
sure to an extent. Even with the generation of inert carbon
dioxide and apparent displacement of atmospheric oxygen
internally, the flammable gasses evidently mixed with suffi-
cient amounts of atmospheric oxygen outside of the enclo-
sure and were ignited by the hot gasses escaping the joint to
produce a higher temperature externally.
Figure 5. Video and infrared camera images of jet flames
emanating from cover joint
Figure 6. Time traces of cover joint and cable entrance
temperatures external to the XP enclosure
Figure 7. Time traces of battery pack and atmospheric
temperatures inside of the XP enclosure
Table 2. Temperatures measured inside of the XP enclosure.
Thermocouple Location
At Thermal Runaway
Onset (°C)
Peak
(°C)
By disk heater 130 1054
Battery backside 61 1009
Battery front side 79 901
Battery side 111 1018
Battery bottom 39 974
Enclosure atmosphere 39 849
respectively, and both were 25 °C at the thermal runaway
onset (Figure 6). No flame was observed from the cable
entrance.
The thermal runaway cascade proceeded rapidly
throughout the battery as indicated by temperature mea-
surements at several battery locations (Figure 7). A post-test
inspection confirmed that thermal runaway occurred in
all of the cells. Table 2 lists battery and enclosure inter-
nal atmosphere temperatures just before and at the peak
of thermal runaway. A higher temperature of 1097 °C was
measured outside of the enclosure (Figure 6). The 1097 °C
measurement is also higher than MH1 cell thermal run-
away temperatures measured within sealed enclosures [10].
Yuan et al. [14] found that the MH1 cell (identified as
NMC 2) thermal runaway produced significant amounts
of inert carbon dioxide gas and flammable gasses including
hydrogen, carbon monoxide, methane, and lesser amounts
of a few heavier hydrocarbons. MH1 cell thermal runaway
produces about 0.66 liters of gas per watt hour of battery
energy [10], corresponding to 283 liters of gas generated by
the 429 Wh battery pack. Gas generation from the battery
should displace atmospheric oxygen from the XP enclo-
sure to an extent. Even with the generation of inert carbon
dioxide and apparent displacement of atmospheric oxygen
internally, the flammable gasses evidently mixed with suffi-
cient amounts of atmospheric oxygen outside of the enclo-
sure and were ignited by the hot gasses escaping the joint to
produce a higher temperature externally.
Figure 5. Video and infrared camera images of jet flames
emanating from cover joint
Figure 6. Time traces of cover joint and cable entrance
temperatures external to the XP enclosure
Figure 7. Time traces of battery pack and atmospheric
temperatures inside of the XP enclosure
Table 2. Temperatures measured inside of the XP enclosure.
Thermocouple Location
At Thermal Runaway
Onset (°C)
Peak
(°C)
By disk heater 130 1054
Battery backside 61 1009
Battery front side 79 901
Battery side 111 1018
Battery bottom 39 974
Enclosure atmosphere 39 849