Battery monitoring device and method

A cell monitoring unit that is configured to monitor a state of a storage battery module including a plurality of parallel cell blocks connected in series, the parallel cell blocks each including a plurality of battery cells connected in parallel, the cell monitoring unit, comprising:

• a current detector that is configured to detect current flowing through the parallel cell blocks;
• a current controller including a mechanical switch or a semiconductor switch;
• a voltage detector that is configured to detect voltage of each of the parallel cell blocks when the current flowing through the parallel cell blocks is a first current value, and when the current flowing through the parallel cell is a second current value;
• and
• a calculator that is configured to:
• calculate a direct-current internal resistance value of each of the parallel cell blocks on the basis of a differential current between the first current value and the second current value, the voltages of the parallel cell blocks at the first current value, and the voltages of the parallel cell blocks at the second current value, and
• perform anomaly determination for the parallel cell blocks on the basis of direct-current internal resistance values of the parallel cell blocks and a maximum value of the direct-current internal resistance values of the parallel cell blocks,
• the anomaly determination including
• calculating a ratio of the maximum value to an average value of direct-current internal resistance values of each of the parallel cell blocks and determining that the parallel cell block is non-normal when the ratio exceeds a preset value,
• calculating a standard deviation of all of the direct-current internal resistance values excluding the maximum value, and
• determining, based on the standard deviation, that there is an anomaly in the parallel cell block, when the maximum value is an outlier relative to the rest of the direct-current internal resistance values excluding the maximum value,
• wherein
• the current controller is configured to stop charging and discharging to and from the storage battery module when the calculator determines the anomaly in the battery cells.