V4Smart, the battery company acquired and renamed by Porsche in March 2025, has unveiled its second-generation cylindrical battery cell, aiming to broaden its customer base with two performance-focused versions that incorporate new silicon-based anode technology from Porsche partner Group14 Technologies.
The German sports car maker purchased Varta’s battery subsidiary V4Drive on March 4, taking a majority stake and renaming it V4Smart. Varta AG retains a minority interest but no operational control. The company, founded in 2022, previously offered a single product — the V21700 UHP-26 booster cell — designed to provide high power for short bursts rather than serve as the primary traction battery in electric vehicles. Porsche was the first and, until recently, the only customer for this specialised concept, which can supplement an EV’s main battery or enhance hybrid systems.
With the new generation, V4Smart is retaining its booster-cell focus but expanding the scope of applications. The cylindrical cell will be offered as the V21700 HP-5X and V21700 (U)UHP-3X. The HP-5X is positioned as the new flagship for broader use cases, while the UHP-3X builds on the previous generation for extreme performance. “The next generation ultra-high power cell delivers up to 900 W of pulse power, making it ideal for extreme-load, thermally demanding environments,” the company said of the UHP-3X. The HP-5X version, it added, offers more than 280 Wh/kg in energy density and over 7,000 W/L in continuous power density, “providing an ideal solution for innovative applications that require both energy and power.”
Compared to the first-generation cell, which achieved 8,420 W/L of power output, the UHP-3X delivers a 75% increase in continuous power density, while the HP-5X achieves double the energy density. Both models use a 21700 format and feature a tabless design to reduce internal resistance and improve thermal management. Testing by Batemo GmbH in the 18650 format showed a capacity of nearly 3.7 Ah, an energy density of 277 Wh/kg, and a power density of 2.73 kW/kg.
The improved performance is attributed to Group14’s silicon-carbon composite anode, which replaces traditional graphite. V4Smart says the new technology opens opportunities beyond automotive use, targeting sectors such as aerospace and power tools. “We are now focusing on industries that require reliable, high-performance cylindrical cells manufactured to the highest quality standards,” the company stated.
Production of the cells began in series at V4Smart’s Ellwangen facility in April 2024, with capacity at its Nördlingen manufacturing centre recently expanded to meet rising demand.