A Nikola battery-electric truck severely damaged in a fire at the company’s Phoenix headquarters last month reignited, raising questions about the safety of battery packs in Nikola trucks delivered to customers.

The fire on Sunday afternoon resulted in no injuries.

Nikola said it is still investigating the original fire with a third-party contractor. The outcome will determine next steps. The company declined to directly answer whether it would file a safety defect, which could lead to a recall, with the National Highway Traffic Safety Administration.

Why the truck caught on fire a second time is unknown. But it points to questions about a reported battery defect in the trucks reported June 27 by the website Electrek.

Romeo Power, a Nikola subsidiary that the company said July 5 it would liquidate, made the battery packs.

Nikola said it suspected foul play in the original fire on June 23 because a car was seen leaving the area just after the fire was reported. Fire investigators so far have found no accelerant to suggest arson.

Defective batteries are suspect in fires

That leaves the batteries themselves as a possible cause. Nikola has kept the damaged trucks in a secure area of headquarters during its investigation.

“This truck was being monitored closely,” Nikola said in a statement to FreightWaves. “In situations such as this where a battery-electric vehicle has had its system compromised, [it] is known to have a higher-than-normal likelihood to reignite, which is why our safety and engineering teams were monitoring as our investigation continues.”

Nikola had a significant safety defect in the battery modules used in its electric semi trucks, Electrek reported June 27. 

The company halted Tre BEV production in May due to excess inventory and slower-than-predicted sales. It is now focusing on a fuel cell-electric version of the truck and will build BEV models only on order.

Laser-welding punctures allow cell corrosion — Electrek

Nikola, which acquired Romeo in an all-stock transaction in August, was Romeo’s biggest customer for Hermes and Legion battery modules. They use two different cell manufacturers which have unique cell dimensions, height offsets, locations, laser parameters and ultimately new welding patterns, Nikola said.

According to Electrek, engineers working on the battery modules last year found corroded battery cells that would self-discharge. Laser welding punctured some of the battery cells in the modules.

The corrosion can create heat generation and increase resistance at the joint, potentially leading to a fire.

“When weld issues were identified at Romeo’s end-of-line process, a quarantine process was implemented which required an inspection of every module,” Nikola said. “To our knowledge and based upon assurances made by Romeo, Nikola did not put any modules with weld issues in our production vehicles.

According to Electrek, Romeo kept manufacturing packs with potentially corroded cells, trying to fix the problem with a running production change.  

Related articles:

Nikola moves to liquidate battery pack maker Romeo Power

Foul play suspected in fire at Nikola headquarters

Nikola acquires struggling Romeo Power to secure battery supply

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