Switch diagnostic device and battery pack including the same

A battery pack comprising:

• pack terminals;
• a battery module comprising cells connected in series and/or in parallel to each other between the pack terminals;
• a first switch connected between a first output terminal of the battery module and a first pack terminal from among the pack terminals at a high voltage side, the first switch being configured to open and close a current path between the pack terminals and the battery module;
• a first voltage-sensing circuit configured to generate a first voltage signal by sensing a voltage across the first switch at the high voltage side;
• a current-sensing circuit configured to generate a current signal by detecting a current flowing through the current path;
• a controller configured to receive the first voltage signal and the current signal, to calculate first contact resistance of the first switch based on the first voltage signal and the current signal, and to diagnose a deterioration state of the first switch based on the first contact resistance;
• and
• a first isolated communication circuit configured to transfer the first voltage signal outputted from the first voltage-sensing circuit to the controller at a low voltage side that is galvanically isolated from the high voltage side,
• wherein the controller is configured to calculate the first contact resistance of the first switch by using the first voltage signal and the current signal detected during a period in which the battery module is being charged with a constant current within a range.