Stellantis and Factorial say they have have reached a significant milestone: the integration of Factorial’s advanced FEST (Factorial Electrolyte System Technology) solid-state battery technology into a Dodge Charger Daytona development vehicle and the launch of a road-testing program to verify performance, safety and reliability. Building on previous validation of automotive-scale FEST cells, this achievement marks the first integration of solid-state cells into a Stellantis vehicle and a breakthrough step towards automotive-grade application.
See also: Factorial Energy goes public at $1.3bn valuation after SPAC merger
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“Battery development is a balancing act. It’s not enough to optimize a single metric. We need a system that delivers real benefits in a real vehicle,” said Ned Curic, Stellantis Chief Engineering and Technology Officer. “This milestone shows we are bringing solid-state batteries closer to our customers with the potential for longer range, faster charging and lower costs. Just as important, FEST®’s strong compatibility with lithium-ion manufacturing processes gives us a critical path to scale this technology.”
In 2025, Stellantis and Factorial demonstrated FEST cells with an energy density of 375 Wh/kg, ultra-fast charging from 15% to 90% in just 18 minutes and robust reliability from -30 °C to 45 °C.
Transitioning from these cell testing results to a development vehicle demanded advanced engineering solutions from Stellantis and Factorial engineers. FEST solid-state battery cells were integrated into the existing battery pack using an innovative, patented new mechanical architecture, designed by Stellantis, to ‘bring out the best of solid-state cell performance’. Engineers also adapted the control systems and pack design to optimize cell performance while meeting rigorous automotive requirements for safety and durability. These technical designs and adaptations are essential for ensuring cell performance in all conditions.
With this integration milestone complete, Stellantis and Factorial say they have started a road testing and calibration program. The testing program will help tune and further verify pack performance and reliability under charging and driving conditions, in addition to vehicle safety.
“We are deeply honored to work alongside Stellantis, one of the world’s great mass-market automakers, on this STLA Large-based development car,” said Siyu Huang, CEO of Factorial. “What we have built together, from cell chemistry to pack architecture to enable real-world road testing, is exactly the kind of deep, full-stack collaboration that solid-state has always required. This milestone doesn’t just validate FEST; it sets a new bar for what automotive-grade solid-state batteries can deliver and supports the development of future vehicles designed to meet the evolving needs of drivers.”
This milestone marks continued progress on Stellantis and Factorial’s previously announced demonstration program, as well as an important step in Factorial’s ongoing development, calibration and industrialization of solid-state batteries for automotive use.
Factorial has a number of automotive backers. Mercedes-Benz, Stellantis, Hyundai, and Kia are among the company’s backers, along with In-Q-Tel, which was set up by the CIA in 1999 as an independent, not-for-profit investment firm.
