Heat exposure from electric vehicle fires: Experimental results and analysis

Free-burning of a Tesla Model 3 and a Chevrolet Bolt was studied under controlled conditions. Heat release rates were estimated from mass loss measurements. Fire-induced heat flux distribution was captured using infrared thermography of high-emissivity plate sensors placed on each vehicle side, supplemented by eight Schmidt-Boelter radiometers. A point-source model (PSM) was used to estimate heat flux over the plate area, allowing comparison with the measured data using an approach that fire safety engineers readily employ.

Plate sensors revealed local peaks in heat flux that were not resolved by the radiometers due to their limited spatial coverage. When measured flame heights were used in the PSM, peak exposures were underpredicted by 1.4% (Bolt) and 18.3% (Tesla). However, when flame heights were estimated from heat release rates, a common assumption in engineering analyses, underpredictions increased to 64.5% (Bolt) and 53.1% (Tesla). Additionally, both plate and radiometer data were used to assess three battery jetting events that occurred before cabin involvement. Jetting-related heat flux peaks ranged from 7.9% to 100% of the global maximum measured during the free-burn, indicating their potentially significant contribution to heat exposure prior to full vehicle involvement.