Lighter, Safer and Smarter Battery Systems: TEMPEST, NEXTBAT and EXTENDED Share Their Results

22 October 2026

The Horizon Europe projects of the BATT4EU Partnership, the public-private partnership between the European Commission and the Batteries European Partnership Association (BEPA), are delivering concrete results across the battery value chain. With the BATT4EU Success Stories webinar series, BEPA gives project coordinators the opportunity to present what their projects have achieved.

This edition focused on the battery system level. The three projects work on packs that are lighter, safer, better monitored and easier to recycle, for applications ranging from electric vehicles and heavy-duty transport to aviation, rail and stationary storage.

TEMPEST

The TEMPEST project develops safe-by-design, lightweight and recyclable battery systems with all-composite housings. Rather than a single solution, TEMPEST built a toolbox of validated, chemistry-agnostic technologies for both Li-ion and semi-solid-state cells. These were applied to three demonstrators targeting small mobility, M1/N1 vehicles and stationary storage.

The project met its –15% weight target on all three demonstrators, with reductions of 50-80% on the smaller demonstrator and around 17% on the largest one. A heat-pipe thermal management system with cold-sprayed conductive coatings reached around 96% of the efficiency of full liquid immersion cooling. An ultrasonic guided-wave structural health monitoring system detects cracks in the housing in about 2.5 seconds, well below the 10-second target, and a spin-off company has been launched to commercialise it.

On safety, an intumescent coating provided up to 15 minutes of thermal barrier protection, helping to prevent fire propagation between vehicles or storage packs. Self-extinguishing internal coatings release CO₂ in case of thermal runaway, while BMS-controlled heating paints, around 75% more efficient than resistive heating, keep cells at the right temperature in cold conditions. For circularity, a debonding-on-command adhesive allows housings to be separated by hand at end of life, and a hydrogen-based recycling route recovers clean metals without acid leaching and turns graphite into value-added carbon products such as carbon nanotubes.

NEXTBAT

The NEXTBAT project develops next-generation battery systems for transport electrification, combining novel pack designs with simulation, AI and battery passport software. The project collected requirements for 10 use cases across road, non-road mobile machinery, waterborne, airborne and rail applications.

NEXTBAT is building two 48 V prototype modules. The high-energy Prototype 1 uses semi-solid-state cells of 350 Wh/kg, as no all-solid-state cells were commercially available, and reaches 5.4 kWh and 262 Wh/kg at module level (without pack casing and auxiliaries). The high-power Prototype 2 combines 75 Ah NMC cells with oil immersion cooling, cell-level impedance diagnostics, active balancing and a laser-welded hybrid aluminium-polymer housing.

With its virtual design tool, the project scaled Prototype 1 up to 800 V battery systems for a heavy-duty truck (735 kWh), a construction machine (956 kWh) and a hybrid regional aircraft (221 kWh). In a hybrid passenger ferry case, immersion cooling limited the cell temperature swing to 3 °C instead of 8 °C with a cold plate, allowing a smaller pack with 18% lower mass. The project also developed degradation-aware AI models to keep the BMS accurate over the battery lifetime, as well as battery passport algorithms with a cloud solution for fleet data.

NEXTBAT is ongoing: validation and abuse testing of the prototypes, a dismantling demonstration and a roadmap towards certification of next-generation battery systems will follow.

EXTENDED

The EXTENDED project develops an adaptable, modular battery pack based on semi-solid-state NMC cells. Its approach is to integrate mechanics, sensing, battery management, thermal control, safety and circularity into one modular platform, designed against requirements from automotive, stationary storage, heavy-duty and aeronautics applications.

The project built three module prototypes with three BMS variants, each with 24 cells. The virtual demonstrator reaches an estimated 173 Wh/kg, with up to 50% weight reduction compared with the defined reference. To bring diagnostics closer to each cell, EXTENDED combined optical infrared daisy-chain communication, single-cell impedance diagnostics integrated in the BMS electronics and printed temperature and pressure sensor arrays, reducing wiring while providing richer cell-level data.

On thermal management and safety, the project achieved a 22% weight saving on the battery thermal management system, a temperature difference below 5 °C in normal operation and no thermal propagation when vented gases are evacuated. Module-level testing, dismantling evidence and the life cycle assessment are being finalised before the project ends on 31 October 2026.

Together, TEMPEST, NEXTBAT and EXTENDED show how European research is moving battery innovation from the cell to the complete system. Lighter composite housings, smarter cell-level monitoring, more efficient thermal management and design for disassembly are making battery packs safer, lighter and more sustainable, across transport and stationary applications. The projects were also open about what remains to be done, from long-term ageing data to industrial scale-up, which is valuable input for the next generation of European battery projects.

These results show the value of a dedicated partnership covering the full battery value chain. With its Battery R&I Blueprint, BEPA calls for continued and strengthened support for battery research and innovation under the next EU Framework Programme, building on the results of BATT4EU.

To meet the battery community and hear more about the latest developments, join us at the Battery Innovation Days on 11–12 November 2026 in Stockholm.