Systems and related methods for supplying power to a medical device employ self-charging serially-connectable portable batteries. A system includes a base module and external battery modules. The base module is operatively coupled with the medical device and includes a base module input connector. Each of the external battery modules includes one or more battery cells, an output connector, an input connector, and a controller. The output connector is configured to output electrical power from the external battery module. The input connector is configured to receive electrical power from another of the plurality of external battery modules. The controller is operatively coupled with the one or more battery cells, the output connector, and the input connector. The controller is configured to control distribution of electrical power received via the input connector to charge the one or more battery cells and/or to be output via the output connector.
