Electric Vehicle Battery Fires

In October 2020, the Office of Defects Investigation (ODI) opened a Preliminary Evaluation (PE) on 2017-2020 Model Year (MY) Chevrolet Bolt vehicles based on complaints received alleging that the vehicles caught fire under the seating area while parked and unattended. At the time, ODI had received 2 Vehicle Owner Questionnaires (VOQs) and several field reports. All complaints alleged vehicles caught fire during or after electrical charging. ODI's review found vehicle thermal events occurred during and/or at the end of the battery module charging cycle. The information learned from NHTSA and General Motors joint vehicle inspections prompted General Motors to file Recall 20V-701 on April 29, 2021. The remedy for this recall included 1) performing diagnostic procedures to identify and replace potentially defective battery cell-module assemblies and 2) installing onboard diagnostic software, designed to detect and warn owners regarding potential issues related to changes in battery module performance over time. Until this interim remedy became available for all affected vehicles, General Motors instructed their customers to enable ?Hilltop Reserve or ?Target Charge Level, based on the vehicle-equipped technology. Enabling these technologies would limit charging capacity of the battery module to a maximum of 90 percent. General Motors then continued to investigate the root cause of these battery cell module thermal events, which would lead them to their long-term recall remedy solution. Utilizing the information obtained from the Recall 20V-701 software update, General Motors and LG Energy Solutions, the supplier of the battery cell module pack along with LG Electronics, determined the root cause of the thermal events to be the result of two simultaneous manufacturing defects occurring in the same battery cell. The defect condition appears to be aggravated by routinely charging the battery to a full or nearly full state of charge after it has been substantially depleted.