EU Project Explored: Could Electric Vehicle Batteries Have Second-Life as Energy Storages?

A large portion of the battery capacity would still be usable even when the vehicles reach the end of their lifespan. Lithium-ion batteries of end-of-life vehicles would have significant capacity remaining for stationary Battery Energy Storage Systems (BESS).

The EU-funded TREASoURcE project has studied this circular economy opportunity and developed recommendations to promote the reuse of batteries. Electric vehicle batteries were tested as energy storage in two locations in Norway and at Lempäälä House in Finland. The pilot sites in Norway were better suited for battery storage use, and negotiations are underway there to continue their use after the project.

Why Favor Reuse Over Recycling?

When an EV battery’s State of Health (SoH) drops to about 70–80 percent of its original capacity, the car’s driving range shortens, and a car equipped with such a battery is no longer considered premium in the used car market. The battery is still the most valuable part of an electric vehicle and can in many cases still be functional for BESS use.

The TREASoURcE project has found that extending the battery lifespan through reuse reduces the need for mining new virgin materials and offers a cost-effective way to support the integration of renewable energy into the electricity grid.

Technical Prerequisites: Not All Batteries Are Equal

One of the project’s key technical findings relates to the large differences between batteries. A battery’s suitability for reuse depends on several factors.

It is not worthwhile to scrap batteries if the materials do not have a high value. More typical NMC batteries (nickel-manganese-cobalt) contain valuable metals, which might make materials recycling economically wiser than secondary use as a battery storage unit. Newer LFP batteries (lithium-iron phosphate), however, may be more suitable for reuse, as they do not contain equally valuable materials.

“Reuse is clearly more successful if the original Battery Management System, or BMS, can be used. This is properly successful if the battery’s original manufacturer permits the reuse solution provider to use the BMS”, says Raimo Tengvall, Senior Specialist from the City of Helsinki Innovation Company, Forum Virium Helsinki.

The remaining capacity and internal resistance of the battery must be reliably tested before reuse. The project emphasised the need for standardized testing methods and better availability of battery data, such as charging history.

Key Steps in Deploying Battery Storage

During the battery storage experiments in Norway and Finland, the TREASoURcE project learned things that are also suitable for deploying battery energy storage systems based on new batteries.

“A battery as an energy storage unit is best suited for sites with an occasional large power requirement: public events, industrial processes, or even high-power charging for electric vehicles”, Tengvall says.

A used and old battery is naturally more likely to fail and, in the worst case, catch fire, for example, due to thermal runaway. In addition to connection permission from the distribution network company, a rescue plan, and a fire suppression system are required. Furthermore, the battery system must work in conjunction with the property’s potential solar panels and other electricity consumption.

Battery rooms do not yet have their own regulations, so the safety of each site must be assessed separately by experts. Therefore, it may be simpler to implement used battery solutions primarily in outdoor spaces.

Challenges Remain

The lessons learned from the TREASoURcE project show that the reuse of EV batteries as energy storage is technically possible, but several obstacles still need to be cleared.

The EU Battery Regulation requires a Digital Product Passport (DPP) starting in 2027, which will contain information on the battery’s origin, service history, and chemistry, among other details. This will significantly ease the evaluation of batteries for reuse. However, such batteries will only begin to become available for reuse in the 2030s–2040s. Additionally, the reasonably affordable prices of new batteries challenge the profitability of reuse, as converting used batteries into energy storage often involves a lot of manual work.

The closed software systems of battery and car manufacturers (OEMs) make it difficult for external operators to assess and control the batteries. Each battery model is different, which prevents automated dismantling and scaling reuse to an industrial scale.

“If processes can be standardised, used electric vehicle batteries could become one part of a flexible energy system—alongside new batteries and other energy storage solutions”, Raimo Tengvall concludes.

The goal of the EU-funded TREASoURcE project is to develop the circular economy in the Nordic countries, the Baltics, Germany, and Poland. The project’s Replication Handbook website compiles the results and operating models found to be functional during the project—including material on plastic recycling and utilising bioeconomy side streams, in addition to batteries.

Main photo: Maija Astikainen, City of Helsinki