Power Supply System Using High-capacity Li-ion Battery

Abstract:
As ICT devices continue to spread rapidly, the effect on society of interruptions to information and communications services due to power outages is becoming greater, and the need for reliable sources of power is increasing. In light of this, we have developed lithium-ion batteries, which have a theoretical energy density three times that of lead-acid storage batteries and can yield reduced size and weight. The lifetime of lithium-ion batteries degrades if they are maintained continuously in a fully charged state, but the lithium-ion batteries we have developed can also be used in this type of environment. For operation as a backup for communications equipment, cells are connected in series to achieve -48 V output, and to secure adequate capacity, these must be connected in parallel. We developed a large-capacity 210 Ah battery, and a battery management system for connecting them in a multi-series-parallel arrangement. A fire retardant was used in the electrolyte of the lithium-ion batteries making them are very safe, and they have passed various safety standards and been certified for very high safety. The storage batteries in the power system are controlled, monitoring various voltages, currents and temperatures and with functions to backup or shut-down safely if an anomaly is detected. Tests were conducted to evaluate the long-term operation of the lithium-ion battery backup power system described above. These test showed that the charging control functions can keep variation among the storage batteries very small, suggesting that they will exhibit excellent performance even over long-term operation.