From EVs to energy storage: CityUHK's breakthrough technology gives retired batteries a second life, advancing the circular economy and energy transition
Electric vehicles (EVs) are playing an increasingly important role in reducing carbon emissions and supporting sustainable development. However, the management and reuse of retired EV batteries have emerged as growing challenges for the global transition to a circular economy.
A research team at City University of Hong Kong (CityUHK) has developed an innovative cascade utilisation battery solution that enables retired EV batteries to be repurposed for energy storage and power quality improvement applications. By integrating smart power conditioner (SPC) and energy management technologies, the solution gives retired EV batteries a new lease of life, transforming them from potential waste into valuable energy assets.
Although retired EV batteries can no longer meet the demanding performance requirements of high-speed vehicle operation, many retain substantial energy storage capacity and remain suitable for less demanding stationary applications, such as battery energy storage systems.
Despite the considerable potential of battery repurposing, large-scale deployment has long been hindered by the lack of standardised processes and an integrated industrial ecosystem covering battery collection, safety inspection, health assessment, grading, repacking, system integration and safety management.
To address these challenges, a team led by Professor Henry Chung Shu-hung, former Chair Professor of Electrical Engineering at CityUHK*, has established a comprehensive technical and operational framework for second-life battery applications. The framework covers the entire value chain, from battery collection, classification and state-of-health assessment to performance testing, system design and integration.
At the core of the innovation is an SPC equipped with autonomous energy routing, real-time health monitoring and advanced safety protection functions. The system can effectively manage battery packs with varying health conditions and configurations, while features such as overcharge protection and self-diagnostic capabilities significantly improve operational stability, reliability and safety.
“This technology has the potential to extend the service life of retired EV batteries by an additional eight to ten years,” said Professor Chung. “Our team has also developed a rapid battery health assessment technology capable of evaluating battery conditions within just three minutes. Compared with conventional methods that may take several hours, the difference in accuracy is within 5%. Once widely adopted, this technology will not only grant retired batteries a second life, but also reduce power losses across the distribution network and lower carbon footprints.”
The team has successfully deployed the technology in a solar-storage-charging system using retired EV batteries, demonstrating the practical viability of second-life batteries in renewable energy applications. The repurposed battery energy storage system can be charged by solar power and discharged to support EV charging for two to three vehicles.
The breakthrough has received wide international recognition. The core technologies are part of multiple patent applications and have won numerous international awards, including the Gold Medal and Best Sustainable Invention of the Year at WorldInvent Singapore 2025, the Gold Medal with Congratulations of the Jury at the 49th and 50th International Exhibition of Inventions Geneva, the Gold Medal at the Silicon Valley International Inventions Festival 2025, and the Silver Award at the 4th Asia Exhibition of Innovations and Inventions.
The project was supported by approximately HK$6.7 million from the HKSAR Government’s Green Tech Fund, with research and development activities conducted between July 2022 and September 2025.
The project also demonstrates strong industry-academia-research collaboration. Through the logistics network of Dah Chong Hong Motor Service Centre, the team established a stable collection channel for retired EV batteries. At the same time, the team worked with E. Tech Management (HK) Limited and MIoT Limited to develop battery diagnostics, grading and testing technologies, while Siemens Limited provided professional support in system design and engineering integration.
The team is now actively pursuing technology transfer and commercialisation opportunities to facilitate the deployment of second-life battery systems in logistics hubs, EV charging facilities and power distribution networks. By extending battery life beyond automotive applications, the technology provides a practical pathway for promoting second-life battery utilisation, strengthening energy storage infrastructure, improving resource efficiency and advancing the development of a circular economy. The project also serves as an important local reference for the wider adoption of repurposed EV batteries in renewable energy and power management applications.
*Professor Chung retired on 1 September 2026.
Media enquiries:
Him Chak, Communications and Institutional Research Office, CityUHK (Tel: 3442 6807 )
A research team at City University of Hong Kong (CityUHK) has developed an innovative cascade utilisation battery solution that enables retired EV batteries to be repurposed for energy storage and power quality improvement applications. By integrating smart power conditioner (SPC) and energy management technologies, the solution gives retired EV batteries a new lease of life, transforming them from potential waste into valuable energy assets.
Although retired EV batteries can no longer meet the demanding performance requirements of high-speed vehicle operation, many retain substantial energy storage capacity and remain suitable for less demanding stationary applications, such as battery energy storage systems.
Despite the considerable potential of battery repurposing, large-scale deployment has long been hindered by the lack of standardised processes and an integrated industrial ecosystem covering battery collection, safety inspection, health assessment, grading, repacking, system integration and safety management.
To address these challenges, a team led by Professor Henry Chung Shu-hung, former Chair Professor of Electrical Engineering at CityUHK*, has established a comprehensive technical and operational framework for second-life battery applications. The framework covers the entire value chain, from battery collection, classification and state-of-health assessment to performance testing, system design and integration.
At the core of the innovation is an SPC equipped with autonomous energy routing, real-time health monitoring and advanced safety protection functions. The system can effectively manage battery packs with varying health conditions and configurations, while features such as overcharge protection and self-diagnostic capabilities significantly improve operational stability, reliability and safety.
“This technology has the potential to extend the service life of retired EV batteries by an additional eight to ten years,” said Professor Chung. “Our team has also developed a rapid battery health assessment technology capable of evaluating battery conditions within just three minutes. Compared with conventional methods that may take several hours, the difference in accuracy is within 5%. Once widely adopted, this technology will not only grant retired batteries a second life, but also reduce power losses across the distribution network and lower carbon footprints.”
The team has successfully deployed the technology in a solar-storage-charging system using retired EV batteries, demonstrating the practical viability of second-life batteries in renewable energy applications. The repurposed battery energy storage system can be charged by solar power and discharged to support EV charging for two to three vehicles.
The breakthrough has received wide international recognition. The core technologies are part of multiple patent applications and have won numerous international awards, including the Gold Medal and Best Sustainable Invention of the Year at WorldInvent Singapore 2025, the Gold Medal with Congratulations of the Jury at the 49th and 50th International Exhibition of Inventions Geneva, the Gold Medal at the Silicon Valley International Inventions Festival 2025, and the Silver Award at the 4th Asia Exhibition of Innovations and Inventions.
The project was supported by approximately HK$6.7 million from the HKSAR Government’s Green Tech Fund, with research and development activities conducted between July 2022 and September 2025.
The project also demonstrates strong industry-academia-research collaboration. Through the logistics network of Dah Chong Hong Motor Service Centre, the team established a stable collection channel for retired EV batteries. At the same time, the team worked with E. Tech Management (HK) Limited and MIoT Limited to develop battery diagnostics, grading and testing technologies, while Siemens Limited provided professional support in system design and engineering integration.
The team is now actively pursuing technology transfer and commercialisation opportunities to facilitate the deployment of second-life battery systems in logistics hubs, EV charging facilities and power distribution networks. By extending battery life beyond automotive applications, the technology provides a practical pathway for promoting second-life battery utilisation, strengthening energy storage infrastructure, improving resource efficiency and advancing the development of a circular economy. The project also serves as an important local reference for the wider adoption of repurposed EV batteries in renewable energy and power management applications.
*Professor Chung retired on 1 September 2026.
Media enquiries:
Him Chak, Communications and Institutional Research Office, CityUHK (Tel: 3442 6807 )