Development of a high performance Ni-MH battery for smaller electric vehicles

摘要

This is a report on the development of a nickel-metal hydride (Ni-MH) battery for smaller electric vehicles developed as near-future urban commuter vehicles. Our goals in the development of this battery were compactness and high performance. This performance was achieved through the development of a medium-capacity 50Ah-class battery. In field tests during the development, uneven battery temperature created capacity imbalances among batteries in the vehicle, which was a major cause of battery deterioration. To solve this problem we developed a new technology to improve the high-temperature characteristics of batteries used in EVs, that raised charging efficiency under high-temperature conditions, Le., the available capacity to as high as 90% at 60°C compared with 100% at 25°C, thereby making it possible to mitigate the capacity disparities among the batteries in the vehicle. Additionally, mitigating the capacity disparities due to temperature differences among the batteries limited the deterioration of batteries used in vehicles and made it possible to maintain long-term high performance.