The 8-cell battery allows the Transcend Travel CPAP to be used in areas where AC power is not provided. The user will have the freedom to use a CPAP machine in remote areas or even during their travel in a car, bus or train. If the user plans on being gone an extended period of time, it is suggested to have a couple of fully charged batteries to ensure the machine will be able to be used without needing to recharge a battery.