Used electric vehicle batteries are not easily disposed of, but they still hold significant value after their initial use in vehicles. These batteries typically retain 70 to 80 percent of their original capacity after about a decade of use, which is enough to make them suitable for stationary energy storage. In France, a startup named Battwoo, founded in 2023, is exploring this growing market by repurposing used batteries for storage systems linked to solar power installations. Battwoo claims its systems are less expensive than new ones and can last much longer before being recycled. The process begins with retrieving batches of used batteries from specialized partners. These batteries undergo a series of diagnostics and tests conducted by an accredited laboratory and internally by Battwoo. Only those showing more than 80 percent of their original capacity are selected. These batteries are then requalified and assembled into battery cabinets in a workshop in Madrid. Each system is customized based on the customer's needs, whether to store surplus solar energy or manage power consumption peaks. Battwoo is not the first in France to explore this niche. Renault had launched its Advanced Battery Storage project in 2018, using electric vehicle batteries for stationary storage. However, Battwoo targets a different market, offering systems of a few hundred kilowatt-hours for professionals with solar panels. According to Battwoo, reconditioned batteries can last 15 to 30 years longer than new ones, and at the end of their second life, they are intended for recycling. The recycling sector in France is still in its early stages, with the first French factory for recycling electric vehicle batteries opening just over a year ago. Battwoo also highlights cost and environmental benefits. A reconditioned 500 kWh battery is about 30 percent cheaper than a new one. The company claims a return on investment of four to seven years, depending on the site. Environmentally, Battwoo estimates that reusing batteries reduces their carbon impact by four times compared to producing new ones. These reconditioned batteries are primarily used by professionals with small solar power plants to increase on-site energy consumption. For example, a padel club in the Hauts-de-France has paired a 350 kWh system with a 250 kWc solar plant to power its evening lighting. Similarly, a local apple cooperative uses a 350 kWh battery to power its cold storage and production lines. Battwoo is currently focusing on projects under 500 kWh to ensure the reliability and safety of its systems before scaling up to larger installations.