Relay Welding Detector of Battery System and Battery System Which Uses the Detector

A method of diagnosing a battery system which comprises:

• a battery module where a plurality of battery cells are connected to each other in series;
• a switching circuit which is connected to the battery module in series, a first relay switch and a second relay switch being connected in series;
• a control unit which controls the first relay switch and the second relay switch;
• and a welding diagnosis circuit which includes a switching element and is connected to a negative pole side of the battery module via the switching element, the method comprising:
• a first step of bringing the first relay switch and the second relay switch into an OFF state;
• a second step of bringing the switching element into an ON state after the first step;
• and
• a third step of determining whether or not a voltage between the first relay switch and the second relay switch is 0V after the second step.

A method of diagnosing a battery system which comprises:

• a battery module where a plurality of battery cells are connected to each other in series;
• a switching circuit which is connected to the battery module in series, a first relay switch and a second relay switch being connected in series;
• a control unit which controls the first relay switch and the second relay switch;
• and a welding diagnosis circuit which includes a switching element and is connected to a negative pole side of the battery module via the switching element, the method comprising the steps of:
• a first step of bringing the first relay switch and the second relay switch into an OFF state;
• a second step of measuring a high-potential-side voltage of the first relay switch after the first step;
• a third step of bringing the switching element into an ON state after the second step;
• and
• a fourth step of determining whether or not a voltage between the first relay switch and the second relay switch is 0V and the high-potential-side voltage of the first relay switch is the same value as the voltage in the second step after the third step.