A circuit assembly (600) includes a printed circuit board assembly (100). The printed circuit board assembly includes a first circuit board (101), a second circuit board (102), and a first flexible substrate (103) interposed between, and continuous with, the first circuit board and the second circuit board. A second flexible substrate (108) extends from, and is continuous with, the second circuit board. One or more electronic circuits comprising electronic components (301,302,303,304,305) are disposed along one or more of the first circuit board or the second circuit board. The printed circuit board assembly is folded about a battery (601), with the first circuit board adjacent to the first major face, the second circuit board adjacent to the second major face, and the first flexible substrate spanning the one or more side faces.