Exterior Insulator For An Implantable Power Source

A polymeric film cover assembly for isolating an electrochemical power source from the other components housed inside an implantable medical device is described. The cover assembly comprises a first shallow-formed shaped-cover of a polymeric film configured to cover a first portion of the exterior surface of the casing and a second shallow-formed shaped-cover of the polymeric film configured to cover a second portion of the exterior surface of the casing. With the first and second shaped-covers contacting the casing, the shaped-covers are connected to each other in an overlapping or butted relationship to substantially or completely cover the exterior surface area of the casing. The interlocking polyester shaped-covers are readily formable into the desired three-dimensional form factor of the casing of power source while maintaining a desirable film thinness.