A battery-powered, modular surgical device, comprising: an electrically powered surgical instrument (116, 118; 303, 304) operable to surgically interface with human tissue; and a handle assembly connected to the surgical instrument (116, 118; 303, 304), the handle assembly having: a removable hand grip (301; 701-703, 704a-n, 706a-n, 2802): shaped to permit handling of the surgical instrument (116, 118; 303, 304) by one hand of an operator; and having an upper portion and a cordless internal battery assembly (701-703, 704a-n, 706a-n) that powers the surgical instrument (303, 304), the internal battery assembly (701-703, 704a-n, 706a-n) having at least one energy storage cell; and a handle body operable to: removably connect at least the upper portion of the removable hand grip (301; 701-703, 704a-n, 706a-n, 2802) thereto and create an aseptic seal around at least a portion of the removable hand grip (301; 701-703, 704a-n, 706a-n, 2802) when connected thereto; and electrically couple the internal battery assembly (701-703, 704a-n, 706a-n) of the removable hand grip (301; 701-703, 704a-n, 706a-n, 2802) to the surgical instrument (116, 118; 303, 304) and thereby power the surgical instrument (116, 118; 303, 304) for interfacing surgically with the human tissue. an electrically powered surgical instrument (116, 118; 303, 304) operable to surgically interface with human tissue; and a handle assembly connected to the surgical instrument (116, 118; 303, 304), the handle assembly having: a removable hand grip (301; 701-703, 704a-n, 706a-n, 2802): shaped to permit handling of the surgical instrument (116, 118; 303, 304) by one hand of an operator; and having an upper portion and a cordless internal battery assembly (701-703, 704a-n, 706a-n) that powers the surgical instrument (303, 304), the internal battery assembly (701-703, 704a-n, 706a-n) having at least one energy storage cell; and a handle body operable to: removably connect at least the upper portion of the removable hand grip (301; 701-703, 704a-n, 706a-n, 2802) thereto and create an aseptic seal around at least a portion of the removable hand grip (301; 701-703, 704a-n, 706a-n, 2802) when connected thereto; and electrically couple the internal battery assembly (701-703, 704a-n, 706a-n) of the removable hand grip (301; 701-703, 704a-n, 706a-n, 2802) to the surgical instrument (116, 118; 303, 304) and thereby power the surgical instrument (116, 118; 303, 304) for interfacing surgically with the human tissue. a removable hand grip (301; 701-703, 704a-n, 706a-n, 2802): shaped to permit handling of the surgical instrument (116, 118; 303, 304) by one hand of an operator; and having an upper portion and a cordless internal battery assembly (701-703, 704a-n, 706a-n) that powers the surgical instrument (303, 304), the internal battery assembly (701-703, 704a-n, 706a-n) having at least one energy storage cell; and shaped to permit handling of the surgical instrument (116, 118; 303, 304) by one hand of an operator; and having an upper portion and a cordless internal battery assembly (701-703, 704a-n, 706a-n) that powers the surgical instrument (303, 304), the internal battery assembly (701-703, 704a-n, 706a-n) having at least one energy storage cell; and a handle body operable to: removably connect at least the upper portion of the removable hand grip (301; 701-703, 704a-n, 706a-n, 2802) thereto and create an aseptic seal around at least a portion of the removable hand grip (301; 701-703, 704a-n, 706a-n, 2802) when connected thereto; and electrically couple the internal battery assembly (701-703, 704a-n, 706a-n) of the removable hand grip (301; 701-703, 704a-n, 706a-n, 2802) to the surgical instrument (116, 118; 303, 304) and thereby power the surgical instrument (116, 118; 303, 304) for interfacing surgically with the human tissue. removably connect at least the upper portion of the removable hand grip (301; 701-703, 704a-n, 706a-n, 2802) thereto and create an aseptic seal around at least a portion of the removable hand grip (301; 701-703, 704a-n, 706a-n, 2802) when connected thereto; and electrically couple the internal battery assembly (701-703, 704a-n, 706a-n) of the removable hand grip (301; 701-703, 704a-n, 706a-n, 2802) to the surgical instrument (116, 118; 303, 304) and thereby power the surgical instrument (116, 118; 303, 304) for interfacing surgically with the human tissue.