Cordless surgical device for cautery and cutting comprising: a control handle including leads and conductors configured to, in use, be coupled to an end effector for cautery and cutting; at least one energy storage cell or battery; a radio-frequency assembly removably connectable to the control handle comprising a radio-frequency signal generating assembly (3530, 3840) including radio-frequency-signal-generating circuitry, characterised in that the battery or energy storage cell is modular and a portion of the control handle defines an aseptically sealable battery holding compartment that is configured to hold the at least one modular energy storage cell or battery and is coupled thereto via the conductors, the aseptically sealable battery or energy storage cell-holding compartment being selectively exposable to the environment to allow user insertion of the at least one modular energy storage cell or battery; the radio-frequency assembly further comprising: a voltage-control circuit and an output couple, the radio-frequency-signal-generating circuitry having a circuitry output, the voltage-control circuit configured to control an output voltage signal used by the radio-frequency-signal-generating circuitry to generate the circuitry output; an interchangeable circuit casing shaped to be removably connected to the control handle, the interchangeable circuit casing housing the radio-frequency signal generating assembly (3530, 3840) and including a removable connection adapted to couple to leads of the control handle and to the output couple being operable to impart radio-frequency signals to the control handle and hence to the end effector when the interchangeable circuit casing connects to the control handle. a control handle including leads and conductors configured to, in use, be coupled to an end effector for cautery and cutting; at least one energy storage cell or battery; a radio-frequency assembly removably connectable to the control handle comprising a radio-frequency signal generating assembly (3530, 3840) including radio-frequency-signal-generating circuitry, characterised in that the battery or energy storage cell is modular and a portion of the control handle defines an aseptically sealable battery holding compartment that is configured to hold the at least one modular energy storage cell or battery and is coupled thereto via the conductors, the aseptically sealable battery or energy storage cell-holding compartment being selectively exposable to the environment to allow user insertion of the at least one modular energy storage cell or battery; the radio-frequency assembly further comprising: a voltage-control circuit and an output couple, the radio-frequency-signal-generating circuitry having a circuitry output, the voltage-control circuit configured to control an output voltage signal used by the radio-frequency-signal-generating circuitry to generate the circuitry output; an interchangeable circuit casing shaped to be removably connected to the control handle, the interchangeable circuit casing housing the radio-frequency signal generating assembly (3530, 3840) and including a removable connection adapted to couple to leads of the control handle and to the output couple being operable to impart radio-frequency signals to the control handle and hence to the end effector when the interchangeable circuit casing connects to the control handle. a voltage-control circuit and an output couple, the radio-frequency-signal-generating circuitry having a circuitry output, the voltage-control circuit configured to control an output voltage signal used by the radio-frequency-signal-generating circuitry to generate the circuitry output; an interchangeable circuit casing shaped to be removably connected to the control handle, the interchangeable circuit casing housing the radio-frequency signal generating assembly (3530, 3840) and including a removable connection adapted to couple to leads of the control handle and to the output couple being operable to impart radio-frequency signals to the control handle and hence to the end effector when the interchangeable circuit casing connects to the control handle.