In this study, our purpose is to recharge the battery of an implanted pacemaker using the electrical energy that is generated by thermoelectric modules. As long as a temperature gradient is applied, it can drive the thermoelectric modules to generate electrical energy. The temperature of the human body is almost constant and will not change considerably. Therefore, there is a natural temperature gradient between the human body and the external environment, which can be used to charge the battery of an implanted pacemaker. This approach can resolve effectively the issue of pacemaker failure resulting from power shortage. In this research, we substitute human skin with pig skin to simulate the temperature gradient between the human body and the external environment. The power generation efficiencies of various types and arrangements of thermoelectric modules were experimentally investigated in this work. The results showed that the number of working days of the implantable pacemaker battery are extended differently by different charging durations of the thermoelectric device. Patients undergo only a single implantation surgery, and they do not need to undergo the surgery again for the rest of their life because of power shortage of the battery, thereby reducing patients’ risks during surgery, which is thus considerably beneficial to the patients.