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Existing technologies estimate electric charge levels by integrating current sensor values, which can accumulate sensor errors, or by using a model based on the same current, voltage and other characteristics of the battery, which may not accurately reflect the degraded capacity of the actual battery. The former accumulates sensor error due to the time required to take measurements, while the latter is susceptible to capacity degradation. Such methods require periodical capacity measurements and battery operation needs to be suspended for up to three hours each time.

Together with a new technology that combines the current and voltage of batteries, Mitsubishi Electric has developed a new algorithm that integrates the two methods to simultaneously estimate current and battery capacity and correct any errors, resulting in highly accurate, real-time estimations of battery-charge levels. The technology also estimates performance degradation, including decreased capacity and increased resistance, in real time and without suspending operation. Further, the diagnostic data provides useful information for maintaining battery systems and reusing degraded batteries.

The monitoring of battery degradation can help to stabilize and extend the operation of large-scale battery systems. Mitsubishi Electric's new technology is expected to enable battery systems to achieve more efficient operation, more efficient energy control and a wider range of usage.