ResMed Power Station II for AirSense 10 and S9 CPAP devices All-in-one external battery for ResMed AirSense 10 and S9 CPAP devices. Lightweight. Ideal for travel. Provides 10-14 hours of back-up power (based on the humidifer and heated tube not being connected), when mains power is not available. Please note this will only work in conjunction with the appropriate DC cable; see below for more information.