A Dodge Charger guinea-pig vehicle has just been fitted with this revolutionary 'solid-state' battery pack for on-the-road testing. There are no details yet on how long this is expected to last and what tests are involved but this practical level of assessment normally suggests imminent application in production vehicle planning.

Global car-making group Stellantis hasn't previously been characterized as a technology pioneer but that seems to be changing. The group, which includes Chrysler, Fiat, Peugeot and Citroen, is becoming a forerunner in the promising progress of a new type of vehicle battery. It's all thanks to its partnership with American battery tech experts at Factorial Energy.

Last year the two companies announced exciting progress on creating an electric-vehicle (EV) battery with a claimed energy density of 375 watt-hours per kilogram (almost double many current EV battery capacities), the ability to recharge from 15 to 90 percent in just 18 minutes and reliability at temperatures ranging from -22 ºF to 113 ºF (-30 ºC to 45 ºC). All that was very impressive – but was not based on in-the-car, on-the-road, real-world testing.

And moving the new battery from the lab bench out onto the road clearly wasn't easy. Stellantis says getting the cells into the development vehicle 'demanded advanced engineering solutions' from both companies. Knowing auto engineers that probably means lots of swearing and finally using a crowbar and lump hammer to make the thing fit. Officially however, Factorial's FEST (Factorial Electrolyte System Technology) solid-state cells were integrated into the existing battery pack using a 'whole new mechanical architecture,' with the Stellantis engineers reworking the control systems and pack design.

These aptly-named Charger experiments reportedly represent the first time that any of the new type of solid-state EV batteries have been integrated into a proper road-going car in North America.

We've been reporting on the game-changing potential for these solid-state batteries for years. The brief bonus is that they promise higher energy density and faster recharging rates. Despite the hype, we've still not seen them in production-spec cars in the US.. until now.

However, we reported last year on similar tests starting in Europe though, via BMW and Mercedes, which also has a link with Factorial. We've seen how Honda is also involved in the chase to be first to bring a solid-state EV to the market, and recently we looked at a seemingly advanced MG project.

We're clearly on the cusp of a breakthrough, with manufacturers eagerly jostling to be first to claim bragging rights for the first solid-state EV on the market. Naturally, we'll keep following new developments as they happen so stay tuned.

In the meantime, here's a brief recap of the tech involved. Solid-state batteries still use lithium as the primary ion donor, the actual upgrade is replacing the traditional 'liquid' or 'gel' electrolyte with a 'solid electrolyte. It's more complex than that of course, because some of the new 'solid-state' batteries, like Factorial's, use a 'semi-solid' electrolyte.