An electric power wheelchair is a wheelchair that is powered by an electric motor (usually using differential steering) rather than manual power. Powered wheelchairs are useful for those terrains where it is not possible to push a manual wheelchair or may require the use of a wheelchair for long distances or where being in a manual wheelchair can be tiring. They can be used not only by people with "traditional" mobility impairments, but also by people with cardiovascular and fatigue disorders. electric power wheelchair designs can be categorized by drive system/chassis, battery, controller, seat, and use. Because they are used as the primary means of movement, they must be of the highest reliability, both electrically and structurally, and are classified as durable medical equipment by Medicare.
There are four common types of electric power wheelchair drive systems: front-wheel drive, mid- or rear-wheel drive, and all-wheel drive. Power wheels are usually a bit larger than rear wheels/casters, and casters are usually larger than those on manual chairs. The center wheel drive electric power wheelchair has casters at the front and rear for a six-wheel layout.
Electric power wheelchair motors are typically powered by 12- to 80-amp-hour, 12-volt rechargeable deep-cycle batteries, with the smaller batteries used in pairs to provide enough power for the chair to last at least a day between charges. These are available in lead acid or lithium batteries. Since lead-acid batteries may not be legally carried onboard without removing them from the wheelchair and securing them in a transport container, lithium batteries are the first choice for electric power wheelchair use. Many electric power wheelchairs come with an onboard charger that plugs into a standard wall outlet; older or more portable models may have separate charger units.
The controller is most commonly an armrest-mounted joystick, which may have additional controls to allow the user to customize sensitivity or access multiple control modes. The controller can be wiggled to help with side shifting. For users who can't use a hand control, there are various alternatives, such as a sip control that works by blowing air at the sensor. In some cases, the controller can be installed for use by the assistant walking behind the chair, rather than the user. Functions include turning one drive wheel forward and the other backward, thus turning within its own length (differential steering) of the ultralight folding electric power wheelchair. Mind-controlled wheelchairs actually work by detecting brain waves or nerve signals from sensors on the scalp or elsewhere, which have been demonstrated in laboratory settings.
Seats on electric power wheelchairs can have different designs. Start with a basic sling seat and back made of vinyl or nylon, some chairs have optional padding, and some have more comfortable seat and back options that may include headrests. Some companies can install their own backrests and seat cushions for people who have an increased need for trunk stability or who are at increased risk of developing bedsores from prolonged sitting. Finally, a professional seating solution for users who need personalized support. Leg rests can be integrated into the seat design and can be electrically adjusted for users who need to change the position of their legs. Electric power wheelchairs may also have room for reclining or reclining facilities for users who cannot maintain an upright seat indefinitely. This feature can also help improve comfort by transferring pressure to different areas for a period of time, or to position the user in a wheelchair when it needs to be lifted.