A battery management system for one or more batteries coupleable to a healthcare delivery system , the one or more batteries coupled to the healthcare delivery system when the system is not coupled to an alternate power supply, the system comprising: a display unit ; a controller coupled to the display unit and programmed: to determine when the healthcare delivery system is coupled to the one or more batteries, to control the display unit to display an initial number corresponding to a time remaining on battery (TROB) when the healthcare delivery system is coupled to the one or more batteries the battery management system being characterized in that the controller is further programmed: to determine if the TROB is within a reserve time range extending up to a reserve range maximum, the reserve range maximum being less than a maximum TROB, wherein said reserve time range is based on energy capacity for the one or more batteries dependent upon battery cycling, battery temperature and final discharge voltage of the one or more batteries and an extreme operational duration for the healthcare delivery system to change the TROB according to an operational state of the healthcare delivery system if the TROB is greater than the reserve range maximum, and to decrease the TROB without regard for the operational state of the healthcare delivery system if the TROB is less than the reserve range maximum. a display unit ; a controller coupled to the display unit and programmed: to determine when the healthcare delivery system is coupled to the one or more batteries, to control the display unit to display an initial number corresponding to a time remaining on battery (TROB) when the healthcare delivery system is coupled to the one or more batteries to determine when the healthcare delivery system is coupled to the one or more batteries, to control the display unit to display an initial number corresponding to a time remaining on battery (TROB) when the healthcare delivery system is coupled to the one or more batteries the battery management system being characterized in that the controller is further programmed: to determine if the TROB is within a reserve time range extending up to a reserve range maximum, the reserve range maximum being less than a maximum TROB, wherein said reserve time range is based on energy capacity for the one or more batteries dependent upon battery cycling, battery temperature and final discharge voltage of the one or more batteries and an extreme operational duration for the healthcare delivery system to change the TROB according to an operational state of the healthcare delivery system if the TROB is greater than the reserve range maximum, and to decrease the TROB without regard for the operational state of the healthcare delivery system if the TROB is less than the reserve range maximum. to determine if the TROB is within a reserve time range extending up to a reserve range maximum, the reserve range maximum being less than a maximum TROB, wherein said reserve time range is based on energy capacity for the one or more batteries dependent upon battery cycling, battery temperature and final discharge voltage of the one or more batteries and an extreme operational duration for the healthcare delivery system to change the TROB according to an operational state of the healthcare delivery system if the TROB is greater than the reserve range maximum, and to decrease the TROB without regard for the operational state of the healthcare delivery system if the TROB is less than the reserve range maximum. <EOS>