Included as standard on the 'Estate' model and on optional accessory with the 'Cottage' and 'Family' models, the exclusive EIO Power Head delivers an amazing depth of cleaning capability. Because it is powered by a high quality re-chargable battery, the Power Head does not draw electrical current from the principal operating system of the vacuum. It is extra power available when needed. When the Power Head is switched to the 'on' position by means of a foot switch, it delivers a powerful brush churning action to vigorously agitate and withdraw caked material and other debris from carpets or other surfaces. When the electrical charge of the battery becomes depleted, simply remove it, insert it into the battery charger and plug it into an electrical outlet for recharging. The unit comes with two batteries. Battery power: 7.2 volts. Batteries do not have "memory". They may be recharged at any stage minimum running time is 30 minutes. Please note that batteries are not charged prior to shipping.