The growth of the electric vehicle (EV) market increases the interest in used batteries, making the evaluation of second life battery degradation and their environmental impact important to understand. This study assesses a nickel manganese cobalt (NMC)–lithium titanate oxide (LTO) battery using the life cycle assessment (LCA) methodology, considering two scenarios for the second life of the battery: the reuse in an EV or its repurpose as stationary storage for energy generated from photovoltaic panels in a Belgian household. Different from the current studies available in the scientific literature, a multidisciplinary approach is adopted. The study includes primary data from ageing tests conducted in a laboratory. A test campaign is performed on new cells to develop a semiempirical NMC-LTO battery model. Other tests are performed on aged cells to evaluate the feasibility of their second life. These long-lasting cells prove to be suitable for reuse, up to 408000 km or 10 years of repurposing as stationary storage. The LCA demonstrates that the second life of the battery is beneficial under certain conditions. The impact of the reuse and repurpose scenarios on climate change are 0.27 kgCO2eq/kWh and 0.22 kgCO2eq/kWh, respectively. Reuse in a vehicle reduces the impact in eight categories, where the manufacturing stage represents more than 54% of the impact. In countries with an electricity mix below 113 gCO2eq/kWh, reuse decreases the impact on climate change. Due to the balance between efficiency loss compared to a new battery and avoided battery production, repurposing reduces the impact on climate change and acidification by 16% and 25%, respectively. The interest in repurposing is higher when the second life duration is higher. The share of batteries that withstand second life is also a critical parameter but highly depends on the battery chemistry and first use conditions.