Several different embodiments of a flexible polymer battery are disclosed in connection with providing a medical therapy. For example, the electrical current from the polymer battery may be used to energize light sources for administering light therapy. In one embodiment, the polymer battery is formed as a substantially elongate structure having one end attached to an internal receiver coil, and the other end attached to a medical device such as a light probe that is adapted to be implanted within a patient's body. The polymer battery thus provides a conductive link between the internal receiver coil, which is electromagnetically coupled to an external transmitter coil for recharging the battery, and the light probe which is energized with current supplied by the flexible polymer battery. In another embodiment, the polymer battery is used to support a substrate on which a plurality of light sources are mounted in spaced-apart array. Yet other forms of the invention include polymer batteries within capsules or bead to energize light sources contained therein. The beads include receiver coils for recharging the polymer battery. Further, because of their small size, the beads or capsules are readily moved or held at a treatment site with an external magnet while therapy is rendered. Since a polymer battery includes very little metal, it is less likely to cause artifacts when the patient's body is imaged.