Stellantis has integrated Factorial’s FEST (Factorial Electrolyte System Technology) solid-state battery cells — previously demonstrated at 375 Wh/kg energy density — into a Dodge Charger Daytona development vehicle and launched a road-testing program. According to the companies, the project marks the first automotive integration of the technology in North America and the first installation of solid-state cells in a Stellantis vehicle. The road tests are intended to verify performance, safety, and reliability under real-world conditions.
Highlights
- Factorial’s FEST solid-state cells are now installed in a Dodge Charger Daytona development vehicle, which the companies describe as the first automotive integration of the technology in North America.
- The cells were integrated into the existing battery pack using a patented mechanical architecture designed by Stellantis.
- In 2025, the partners demonstrated FEST cells with 375 Wh/kg energy density and charging from 15% to 90% in 18 minutes.
- The development vehicle is the first in the companies’ previously announced multi-stage development vehicle program.
From Cell Validation to a Running Vehicle
The integration builds on the partners’ earlier validation of automotive-scale FEST cells. In 2025, Stellantis and Factorial reported cells achieving an energy density of 375 Wh/kg, charging from 15% to 90% in 18 minutes, and reliable operation from -22°F to 113°F (-30°C to 45°C).
Moving from cell-level results to a development vehicle required new engineering work from both companies. The FEST cells were fitted into the existing battery pack through a patented mechanical architecture designed by Stellantis to support solid-state cell performance. Engineers also adapted the control systems and pack design to balance cell performance against automotive requirements for safety and durability.
“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.”
Road Testing and Calibration Underway
With the integration complete, Stellantis and Factorial have started a road-testing and calibration program. The program will tune and further verify pack performance and reliability under charging and driving conditions, along with vehicle safety.
The development vehicle is built on the STLA Large platform and represents the first vehicle in the multi-stage development vehicle program the companies announced earlier in their partnership.
“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.”
The companies state the milestone continues their previously announced demonstration program and supports Factorial’s ongoing development, calibration, and industrialization of solid-state batteries for automotive use. For prior coverage, see The EV Report’s reporting on the demonstration fleet announcement and the FEST cell validation milestone.
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