Overcharge protection device and method including diagnostic function

An overcharge protection device including a diagnostic function, comprising:

• a mechanical overcharge protection device including at least one Runaway Arresting Device switch electrically connected between a relay actuation coil of a main relay and a ground,
• the at least one Runaway Arresting Device switch comprising a push button coupled to one side of a battery, and moving together in a direction of expansion according to an expansion of the battery, a travelling contact extended to the push button and moving in response to a physical movement of the push button, and a plurality of stationary contacts fixedly coupled to the at least one Runaway Arresting Device switch so as to be electrically connected or disconnected with the travelling contact within a movable range of the travelling contact;
• a control unit for diagnosing whether or not an overcharge protection operation of the mechanical overcharge protection device has been performed and whether the mechanical overcharge protection device is in a normal state or a failed state by detecting a voltage between two ends of the mechanical overcharge protection device;
• and
• a relay actuation switch connected to the relay actuation coil in series, for controlling an opening or shorting of a relay switch of the main relay by supplying or not supplying the voltage to the relay actuation coil by being shorted or opened according to a control signal of the control unit,
• wherein, when the degree of swelling of the battery is equal to or greater than a predetermined value, the push button moves the travelling contact in the direction of expansion of the battery to release the electrical connection between the travelling contact and the stationary contacts to release the connection between the relay actuation coil of the main relay and the ground, and
• wherein, when the control unit determines the mechanical overcharge protection device is in the failed state, the control unit opens the switch of the main relay by interrupting a supply of voltage applied to the relay actuation coil of the main relay by controlling the relay actuation switch to open.