According to one embodiment, a medical device may include an energy supply. The energy supply may include a lithium-ion polymer battery including at least two battery stacks and a control unit. One of the at least two battery stacks may be a backup energy source. The control unit may monitor and control the energy supply such that when the control unit detects a fault in the at least two battery stacks, the control unit disconnects a faulty battery stack. The energy supply may be rechargeable. Each of the at least two battery stacks may include a positive potential terminal, a negative potential terminal and one or more battery cell.