## 2 Materials and Methods
### The Preparation of the Experiment  
For measurement purposes, the Almemo 2690-8 datalogger (Ahlborn, Holzkirchen, Germany) was used, as shown in Figure 6a. It is a universal combined handheld measuring instrument with five universal inputs and two outputs. The device has internal memory, which allows for the direct recording of measured values in the instrument. Furthermore, the device features a large graphical display and waterproof connectors meeting the IP54 protection rating. The device is resistant to splashing water and dust. The temperatures were measured by 4 NiCr-Ni thermocouples with a temperature range of 100 \({}^{\circ}\)C to 1000 \({}^{\circ}\)C. The thermocouples were connected to the Almemo 2690-8. The meteorological conditions were measured by an external weather station shown in Figure 6b,c. To record the course of the experiments, 2 video cameras and 2 thermal imaging cameras with 4 tripods were used.  
The experiments were recorded with a thermal camera FLIR E96 14\({}^{\circ}\) (FLIR, Portland, OR, USA) shown in Figure 6d. The thermal camera FLIR E96 14\({}^{\circ}\) features a resolution of 640 \(\times\) 480 pixels (VGA) and is capable of generating video recordings. The device can be set to three modes based on temperature range, specifically \(-\)20 to +120 \({}^{\circ}\)C, 0 to +650 \({}^{\circ}\)C, and +300 to +1500 \({}^{\circ}\)C, all with a tolerance deviation of \(\pm\)2%. The thermal imaging camera was configured with an ambient temperature of 26 \({}^{\circ}\)C and relative humidity of 30%. The camera recording was set to measure the hot spot (temperature measurement at the hottest point) and simultaneously the average temperature within the set area, in the temperature range mode of 0-650 \({}^{\circ}\)C and 300-1500 \({}^{\circ}\)C. To ensure stability, the thermal imaging camera was mounted on a tripod.  
Figure 5: High-voltage traction battery used in large-scale fire test.  
The placement of thermocouples was designed based on previous experiences with large-scale vehicle fire tests and the size of parking spaces according to the technical regulation STN 73 6058 [24]. This technical standard determines the width of parking spaces in the Slovak Republic. It was also necessary to consider the increase in vehicle dimensions, as noted by the authors in their publication [25]. The placement of thermocouples during the large-scale ICEV test is shown in Figure 7:  
* T0 on the driver's side at a distance of 0.7 m and a height of 1 m;
* T1 inside the vehicle approximately in the middle at headrest height;
* T2 on the roof of the vehicle approximately in the middle (contact point of the car fire blanket and vehicle);
* T3 on the passenger side at a distance of 0.7 m and a height of 1 m.  
A similar placement was considered for the HTB fire test. Thermocouple T1 was placed at the point of connection of the HTB to the vehicle. The thermocouple inside was placed on the opposite side of the initiation to monitor the transfer of fire between the cells. The placement of thermocouples is shown in Figure 8:  
Figure 6: (**a**) Datalogger Almemo 2690-8; (**b**) weather station; (**c**) display for weather station; (**d**) Thermal imaging camera FLIR E96 14°.  
Figure 7: Scheme of location of thermocouples in large-scale ICEV fire test. (**a**) Front view of thermocouple location for large-scale ICEV fire test; (**b**) top view of thermocouple location for large-scale ICEV fire test.  
To initiate the HTB, the transport structure was modified on one side. The HTB fire was initiated by mechanically compromising the integrity of the battery packing. For breaking through, a method of puncturing with a wedge was used. Flame combustion appeared only after the second drive in of the wedge by a hammer.