The Caire FreeStyle Comfort 16-cell battery delivers you with double the battery life compared to the smaller Caire FreeStyle Comfort 8-cell battery. This just means you get double the time to experience, cord and hassle free! With the 16-cell battery, you can enjoy up to 8 hours of portable oxygen therapy on a setting of 2. Now you can definitely bid farewell to worries about running out of oxygen and hello to the freedom to explore, engage, and embrace every moment. While each FreeStyle Comfort comes equipped with an 8-cell lithium-ion battery, many of our customers choose to upgrade to the 16-cell battery, for the simple fact of double the battery life! Sure it makes the overall weight of the unit increase slightly, but most don't mind when they are getting double the battery life of the standard 8-cell battery. Battery life ranges from up to 16 hours on setting 1 to 4 hours on setting 5.