Hello from Editor Z. Solid-state battery news usually means the same thing: a lab slide, a booth demo, and a production promise for "sometime later this decade." Not this time. Stellantis has confirmed it built a real Dodge Charger Daytona solid-state battery test mule using Factorial's FEST cells and has started driving it on public roads — the first time solid-state cells have gone into a Stellantis vehicle for genuine, real-world verification rather than a stage prop.
What's Actually Sitting in the Pack
The FEST Cell's Numbers
Factorial's semi-solid-state FEST cells are rated at 375 Wh/kg, well above the roughly 200-300 Wh/kg typical of the lithium-ion cells in most EVs on sale today. Stellantis says the cells can charge from 15% to 90% in 18 minutes and keep working across a temperature range of -22°F to 113°F — wide enough to cover a genuinely brutal winter and a genuinely brutal summer without special-casing the car.
Built to Drop Into the Existing Pack
The more interesting detail is mechanical, not chemical. Stellantis engineered a patented pack architecture that lets Factorial's solid-state cells slot into the Charger Daytona's existing battery pack structure, rather than demanding an entirely new pack design or platform. That's the part that makes this more than a curiosity: a battery chemistry that can be swapped into hardware Stellantis already builds is a much shorter path to production than one that requires starting the pack from scratch.
Why a Charger Daytona, Why Now
First Integration, First Road-Test Program
Stellantis says this marks the first time solid-state cells have gone into one of its vehicles, and it's launching a road-testing program to match — meant to validate performance, safety, and reliability under real driving and charging conditions rather than in a controlled lab environment. That's a meaningfully higher bar than a press-release milestone, and it's the reason this story reads differently than most solid-state announcements.
A Partnership Years in the Making
This didn't happen overnight. Stellantis invested $75 million in Factorial back in 2021 and signed a joint development agreement the same year, as part of a broader plan to bring solid-state batteries to its lineup by the middle of this decade. Stellantis Chief Engineering Officer Ned Curic called the demonstration fleet "an important milestone" in the partnership, pointing to improved performance, longer driving range, and faster charging as the payoff. Factorial CEO Siyu Huang said solid-state technology "can play a crucial role in enabling the next generation of EVs." The Charger Daytona test vehicles reportedly ride on Stellantis' STLA Large multi-energy platform, the architecture meant to eventually span electric SUVs and performance vehicles across Jeep, Dodge, Chrysler, Alfa Romeo, and Maserati.
The Charger Daytona Could Use the Help
It's worth saying plainly: the electric Charger Daytona has not had an easy run commercially, and range and charging speed have been among the most persistent criticisms since launch. A battery upgrade that can retrofit into the car's existing pack, without forcing Stellantis to redesign the platform underneath it, is about as direct a fix as the company could realistically pursue for that specific complaint — assuming the road testing holds up.
Stellantis Isn't the Only One Testing Right Now
ProLogium's 381 Wh/kg, With Mercedes Watching
On September 2, 2026, Mercedes-Benz's solid-state technology partner ProLogium announced its Generation 3.5 Lithium Ceramic Battery had reached 381 Wh/kg and 903 Wh/L in a 185.4 Ah cell, now in production at 0.5 GWh initial capacity at its Taoyuan facility, with plans to expand toward 1-2 GWh. ProLogium reports cumulative shipments past 2.4 million cells, though most of that volume is consumer and specialty products rather than EV traction batteries — a reminder that a strong cell-level number doesn't automatically translate into a smaller or lighter pack in a showroom car.
Chery Joins the Conversation
A day later, at the September 3 World Power Battery Conference, Chery revealed its own solid-state battery plans, targeting real-world testing in 2027.
| Player | Headline Spec | Status |
|---|---|---|
| Stellantis / Factorial FEST | 375 Wh/kg, 18-min fast charge | Road testing in a Charger Daytona mule |
| Mercedes-backed ProLogium | 381 Wh/kg, 903 Wh/L | In production at 0.5 GWh, scaling up |
| Chery | Not yet detailed | Real-world test plans announced, targeting 2027 |
Three solid-state announcements inside two weeks isn't a coincidence — it's a sign that automakers and battery makers have decided lab demos no longer move the needle, and that putting real hardware on real roads is the new way to prove a chemistry is ready. Whether Stellantis' retrofit-friendly pack architecture or ProLogium's production head start ends up mattering more for actual EV buyers is the question worth tracking into 2027. We'll keep watching the road tests.
-EditorZ
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