70,000Wh energy storage system built with old EV batteries retains over 90% capacity

A German startup has given old e-scooter batteries a second life by using them to develop a high-performance, affordable, and sustainable 70-kilowatt-hour (kWh) energy storage system for industrial use.

The technology was designed by EDENenergy, a Freiburg-based cleantech startup and spin-off of the Fraunhofer Institute for Solar Energy Systems (ISE). It relies on modular units and advanced power electronics to connect used batteries into one larger energy storage system.

Florian Bierwirth, EDENenergy CEO and co-founder highlighted the importance of repurposing old batteries. “It allows different storage units to be connected and enables communication with various modules without having to disassemble the batteries,” he said.

According to the team, the batteries can retain over 90 percent of their original capacity, which makes them suitable for reuse in industrial energy storage. They could also enable businesses to store excess solar power while reducing battery waste.

Old batteries reused

Reports indicate that about one million batteries from e-bikes and e-scooters are prematurely discarded in Germany each year. However, many of them still have enough capacity to remain useful for several more years.

Reusing these batteries has been difficult because they come in different designs, cell types, and battery management systems. To address this, former Fraunhofer ISE researchers developed power electronics that can connect different batteries without dismantling them.

The EDENenergy research team. Credit: EDENenergy

The startup initially focused on batteries from large e-scooter fleet operators to ensure a consistent supply of compatible units. Its first industrial storage system combines 112 used e-scooter batteries, each tested before installation.

While the team initially expected the batteries to retain around 80 percent of their original capacity, tests on the first 350 units revealed that some retained well over 90 percent. The firm delivered its first storage system to a customer last month.

“In mid-October, we delivered the first storage system to a customer, which was an important milestone for our young company,” Bierwirth highlighted. “With this storage size, we initially aim to target medium-sized companies in the region that have a photovoltaic system but do not yet have a storage solution.”

Keeping storage capacity

EDENenergy said that the technology is also modular. This means that individual batteries can be replaced without shutting down the entire system. According to the company, municipal utilities could use it to reduce peak electricity demand, increase solar power consumption, or trade electricity.

The startup will also remotely monitor the batteries to check their condition and determine when individual modules need to be replaced. Once a battery reaches the end of its useful life, it is removed and sent to recycling partners.

Moreover, the system could maintain its full 70 kWh capacity even after 10 years. By comparison, conventional battery storage manufacturers typically guarantee around 80 percent of the original capacity after a decade.

At the same time, the batteries could last longer in stationary applications as they experience fewer vibrations and temperature fluctuations. “In stationary storage systems, where – unlike in their first life – they are exposed to fewer vibrations or temperature fluctuations, these batteries can continue to perform well for several more years,” the company concluded in a press statement. Moving forward, the team plans to expand its industrial storage systems to 300 kWh.