A battery safety device is provided, which may be disposed inside a battery, and may include a conductive handle and a temperature-controlled expansion element. The conductive handle may include a connection portion, a left extension portion, a right extension portion, a top extension portion and an actuating sheet. The left extension portion and the right extension portion may be connected to the connection portion and contact the first conductive portion of the polar winding of the battery. The top extension portion may be connected to the connection portion and contact the first electrode terminal of the battery. The actuating sheet may be connected to the connection portion, and there may be an accommodating space between the actuating sheet and the polar winding, and the temperature-controlled expansion element may be disposed in the accommodating space and contact the actuating sheet and the first conductive portion.