The Transcend P4 battery provides 7 hours of charge for all Transcend CPAP devices. The charger is the size of a deck of cards, allowing patients to easily travel and camp with all of their equipment. The charger is compatible with AC, DC and solar power adaptors, all of which allow a patient to receive treatment in areas without power whether they are traveling, camping or experiencing a power outage due to a storm. This charger is not meant to charge the Transcend heated humidifier. The battery will continue to charge while connected to the to the machine.