Experimental Temperature and Heat Flux Data for Constant Power Over Heating Tests of 18650 and 26650 LFP Cells.

18650 (1.6 Ah) and 26650 (3.3 Ah) LFP cells were tested under constant-power abuse conditions. Heating was applied using a nickel-chromium high-resistance wire wound around the cell surface. The heating power was set to 40 W and 80 W, respectively, to normalize heating relative to cell size. Battery off-gas was ignited by a continuous spark . A detailed methodology is provided in the related publication [link TBC, insert after publication]; see Figures 1 and 3. Cell temperatures, flame temperature, and heat flux were recorded throughout each test. Mass was also measured using a load cell, although readings were affected by signal drift and electromagnetic interference. Therefore, mass loss is reported as the difference between the pre- and post-test measurements. Test results are stored in files named YYMMDD-000.csv , which can be cross-referenced with sample data in LFP_ConstPower_Record.xlsx (see “ Test ID short ”). Each CSV file includes cell, flame, and environmental temperatures (°C), cell temperature rate (°C/s), and heat flux (kW/m²). LFP_ConstPower_Record.xlsx contains additional metadata: cell capacity, pre- and post-test mass, cell form, ignition attempt details, and post-test observations. Data is presented from t = 0 s until the heater is switched off or power is lost (in one case, data is truncated shortly after thermal runaway). A total of 27 experimental runs were conducted: 23 with 18650 cells (12 with ignitor applied, 11 without ignitor applied) and 4 with 26650 cells (all with ignitor applied). Battery safety testing was conducted at the University of Sheffield, with heat flux sensors provided by King’s College London, and the experimental design was developed collaboratively between the two institutions. This work was funded by the UKRI through the Faraday Institution's SafeBatt project.