Battery monitoring system and battery monitoring apparatus

A battery monitoring system comprising:

• a plurality of battery monitoring apparatuses respectively associated with battery packs, each of the battery monitoring apparatuses including:
• a setting unit that:
• sets a communication system to at least one of:
• a first communication system establishing communication between the plurality of battery monitoring apparatuses regularly every time a first communication period elapses;
• and
• a second communication system establishing communication between the plurality of battery monitoring apparatuses regularly every time a second communication period elapses, the second communication period being shorter than the first communication period;
• during a failure diagnosis to be performed in a start-up of the corresponding battery monitoring apparatus:
• sets the communication system to the second communication system initially;
• and
• when communication using the second communication system fails, sets the communication system to the first communication system;
• and
• after the failure diagnosis, sets the communication system to the first communication system;
• and
• a communication unit that:
• communicates with another battery monitoring apparatus of the plurality of battery monitoring apparatuses by using the communication system set by the setting unit;
• and
• during the failure diagnosis, communicates with the other battery monitoring apparatus by using the first communication system when communication using the second communication system fails,
• wherein the communication units of the plurality of battery monitoring apparatuses collectively communicate an event result in the first communication system, and collectively communicate an event result each time an event is terminated in the second communication system.