Battery monitoring system

A battery monitoring system for monitoring a state of a battery pack including n (n:

• an integer) pieces of battery cells connected in series over a plurality of stages, comprising:
• an input circuit to which respective voltage signals of the battery cells are inputted;
• a multiplexer configured to:
• select a battery cell for voltage detection from the n pieces of battery cells;
• select voltage signals inputted from the input circuit;
• and
• output the selected voltage signals;
• a self-diagnosis voltage generation circuit configured to generate a self-diagnosis voltage for diagnosing a failure status of the battery monitoring system itself;
• a first voltage measuring circuit configured to measure a voltage signal in a first route inputted through the multiplexer, based on the self-diagnosis voltage generated from the self-diagnosis voltage generation circuit or based on the voltages of the battery cells inputted from the input circuit;
• a second voltage measuring circuit configured to measure a voltage signal in a second route inputted through the multiplexer at the same time when the first voltage measuring circuit measures the voltage signal in the first route, based on the self-diagnosis voltage generated from the self-diagnosis voltage generation circuit or based on the voltages of the battery cells inputted from the input circuit;
• a comparator configured to compare a measurement result by the first voltage measuring circuit with a measurement result by the second voltage measuring circuit;
• and
• a control unit configured to:
• judge a presence or absence of a failure in a measuring route connected to the first voltage measuring circuit or the second voltage measuring circuit and a failure of the first voltage measuring circuit itself or the second voltage measuring circuit itself, based on a comparison result by the comparator;
• and
• control the input circuit, the multiplexer, the comparator, and the self-diagnosis voltage generation circuit.