German car maker Mercedes Benz, is quietly continuing with the solid-state battery trials it announced on February 24, 2025. Being solid-state means the batteries have safer, solid electrolytes, unlike the industry standard lithium-ion. We visited the Mercedes solid state battery page, to see what we could learn about their project to increase driving range.
25% Longer Range With Mercedes Solid-State Batteries
The German car maker teamed with battery manufacturer Factorial, to develop the first road-ready Mercedes solid–state battery. We find the original word ‘factorial’ interesting, because it refers to a part, or constituent of a greater whole.
Setting that intriguing thought aside, we can confirm that Factorial delivered the first lithium-metal solid-state battery cells to Mercedes a year ago. These cells were an industry first, because they incorporate Factorial’s Electrolyte System Technology (FEST).
The Factorial company makes some quite remarkable claims about its FEST product on its website. These include a targeted 600-mile driving range , 40% less weight, and 30% smaller than lithium-ion batteries. This combination should deliver quite a dramatic improvement in energy-to-weight, and energy-to-volume densities!
Mercedes-Benz predicts that FEST’s potential should deliver a 600-mile-plus driving range. This represents a 25% improvement over the performance of its current, all-electric, EQS 450+ rear-wheel-drive sedan. We were naturally curious to know how the trials were progressing.
The Solid Battery is Trialing in a Modified EQS

Elektrek website confirms that Mercedes-Benz in conducting ongoing laboratory and road trials of the Factorial battery cells. The test bed continues to be a modified EQS prototype. This contains the solid-state battery pack that subsidiary Mercedes AMG High-Performance Powertrains developed.
Markus Schäfer, Mercedes-Benz head of development told reporters, “We expect to bring the technology into series production before the end of the year.” However, Inside EVs website suggests the car itself will only be ready by the end of the decade.
More Information
The Toyota Solid-State Battery Project