An intra-aortic balloon pump system comprising: a pump for inflating and deflating a balloon of an intra-aortic balloon catheter; a first power source for supplying power to the pump; a second power source for supplying power to the pump; and a power supply system; the power supply system being characterized by: a first housing part configured to removably receive the first power source through a first opening of the first housing part; a second housing part configured to removably receive the second power source through a second opening of the second housing part; and a lock element movably positioned with respect to the first and second housing parts (45, 47) to prevent simultaneous removal of the first and second power sources (26, 28) from the first and second housing parts (45, 47), wherein the lock element is configured to secure the first power source within the first housing part when the second power source is removed from the second housing part and wherein the lock element is configured to secure the second power source within the second housing part when the first power source is removed from the first housing part, and wherein the lock element is configured to secure the first power source within the first housing part and to secure the second power source within the second housing part when both the first power source and the second power source are disposed within the first housing part and the second housing part, respectively. a pump for inflating and deflating a balloon of an intra-aortic balloon catheter; a first power source for supplying power to the pump; a second power source for supplying power to the pump; and a power supply system; the power supply system being characterized by: a first housing part configured to removably receive the first power source through a first opening of the first housing part; a second housing part configured to removably receive the second power source through a second opening of the second housing part; and a lock element movably positioned with respect to the first and second housing parts (45, 47) to prevent simultaneous removal of the first and second power sources (26, 28) from the first and second housing parts (45, 47), wherein the lock element is configured to secure the first power source within the first housing part when the second power source is removed from the second housing part and wherein the lock element is configured to secure the second power source within the second housing part when the first power source is removed from the first housing part, and wherein the lock element is configured to secure the first power source within the first housing part and to secure the second power source within the second housing part when both the first power source and the second power source are disposed within the first housing part and the second housing part, respectively. a first housing part configured to removably receive the first power source through a first opening of the first housing part; a second housing part configured to removably receive the second power source through a second opening of the second housing part; and a lock element movably positioned with respect to the first and second housing parts (45, 47) to prevent simultaneous removal of the first and second power sources (26, 28) from the first and second housing parts (45, 47), wherein the lock element is configured to secure the first power source within the first housing part when the second power source is removed from the second housing part and wherein the lock element is configured to secure the second power source within the second housing part when the first power source is removed from the first housing part, and wherein the lock element is configured to secure the first power source within the first housing part and to secure the second power source within the second housing part when both the first power source and the second power source are disposed within the first housing part and the second housing part, respectively.