wheelchairs An electric-powered wheelchair, commonly called a "powerchair" is a wheelchair that additionally incorporates batteries and electric motors into the frame and that is controlled by either the user or an attendant, most commonly via a small joystick mounted on the armrest, or on the upper rear of the frame. Alternatives exist for the traditional manual joystick, including head switches, chin-operated joysticks, sip-and-puff controllers or other specialist controls, which may allow independent operation of the wheelchair for a wider population of users with varying motor impairments. Ranges of over 10 miles/15 km are commonly available from standard batteries. Powerchairs are commonly divided by their access capabilities. An indoor-chair may only reliably be able to cross completely flat surfaces, limiting them to household use. An indoor-outdoor chair is less limited, but may have restricted range or ability to deal with slopes or uneven surfaces. An outdoor chair is more capable, but will still have a very restricted ability to deal with rough terrain. A very few specialist designs offer a true cross-country capability. Powerchairs have access to the full range of wheelchair options, including ones that are difficult to provide in an unpowered manual chair, but have the disadvantage of significant extra weight. Where an ultra-lightweight manual chair may weigh under 10 kg, the largest outdoor power-chairs may weigh 200 kg or more. Smaller power chairs often have four wheels, with front or rear wheel drive, but large outdoor designs commonly have six wheels, with small wheels at front and rear and somewhat larger powered wheels in the centre. A power-assisted wheelchair is a recent development that uses the frame and seating of a typical rigid manual chair while replacing the standard rear wheels with wheels of similar size which incorporate batteries and battery-powered motors in the hubs. A floating rim design senses the pressure applied by the user's push and activates the motors proportionately to provide a power assist. This results in the convenience, and small size of a manual chair while providing motorised assistance for rough/uneven terrain and steep slopes that would otherwise be difficult or impossible to navigate, especially by those with limited upper-body function. As the wheels necessarily come at a weight penalty it is often possible to exchange them with standard wheels to match the capabilities of the wheelchair to the current activity. Mobility scooters Mobility scooters share some features with powerchairs, but primarily address a