Nikola Electric Truck Fire Likely Due to Battery Pack Leak
Nikola Motors has issued a voluntary recall for 209 of its Class 8 Tre battery electric vehicles as a precautionary measure following the findings of a third-party investigation into a recent truck fire.
Nikola Motors has released the preliminary results of its battery pack investigations following a June truck fire at its corporate headquarters in Phoenix.
Nikola Class 8 Tre battery electric truck. Image used courtesy of Nikola Motors
The investigation by Exponent, an independent third-party investigator, produced preliminary findings indicating a coolant leak inside a single battery pack of the vehicle was the fire’s likely cause. A minor thermal incident with a single battery pack on an engineering validation truck on August 10, 2023, further corroborates these findings. There were no injuries involved in either incident.
Prioritizing Safety and Corrective Action
Based on video evidence of the June 23 event, Nikola initially suspected foul play may have been involved, but this theory was dismissed following further investigation.
Internal investigations by the Nikola team indicate that a component from a single supplier is the likely source of the pack failures, and corrective actions are being developed. In the interim, Nikola has issued suggested actions to be taken by customers and dealers to help detect and prevent potential problems with their trucks.
Additionally, the company uses vehicle software systems to monitor trucks in the field in real-time. According to Nikola, only two battery packs have experienced thermal events out of the 3,100 packs deployed on production vehicles.
The company is filing its voluntary recall with the National Highway Traffic Safety Administration (NHTSA) and has issued a temporary hold on new BEV sales.
Engineering Challenges of High-Density Power Conversion and Storage
Energy density is essential to EV performance to get the most range and fastest vehicle charging time. But high-density power conversion and storage introduce significant engineering challenges with potential implications for safety and reliability.
Nikola Tre BEV performance specifications. Image used courtesy of Nikola Motors
Lithium-ion is the leading rechargeable battery type used in EVs due to its high energy density. High energy density means more energy can be stored in a smaller physical space, and a smaller battery pack means a lighter vehicle with a longer range, faster charging time, and lower cost – essential characteristics for e-OEM manufacturers in a competitive EV market.
Due to their large size, commercial vehicles' energy and power requirements, like Class 8 trucks, are even higher than passenger vehicles.
Weighing in at 82,000 pounds, Nikola’s Class 8 Tre BEV is rated at 645 Hp, allowing it to travel up to 70 mph, and has an operating range of 330 miles on a fully charged battery pack.
The battery comprises nine packs with a total capacity of 733 kWh and can take an 80% charge in 90 minutes.
Nikola has traditionally sourced its lithium-ion batteries from LG Energy Solution but signed a separate battery supply agreement with Proterra Inc. in January 2022.
Nikola Tre drivetrain. Image used courtesy of Nikola Motors
Thermal Runaway and EV Battery Hazards
With their high energy densities, lithium-ion battery pack fires are a potential safety hazard for EVs, and robust battery management systems (BMS) are required to eliminate or minimize their occurrence.
The electrolyte used in lithium-ion batteries is flammable. If a short circuit occurs in any of a pack’s cells, the electrolyte can heat to the point of failure of the cell’s physical enclosure. Once breached, the flammable electrolyte can migrate to adjacent cells creating an uncontrolled thermal runaway event or battery fire.