Electric wheelchairs are usually a lot heavier than manual wheelchairs because the frame has to be stronger in order to support the battery and motors. The level of sophistication in electric wheelchairs also varies widely, from just using standard batteries and a joy stick controller, right up to using microprocessor controlled gyroscopic circuitry which enables the chair to rise on two wheels!
Because the level of sophistication varies so widely, so do the prices, from around £1000 - £16000 ($1900 - $30000). The latest and most high tech wheelchair at the moment, is the iBOT. The iBOT mobility system can climb stairs, bump up curbs, glide through gravel and even elevate a seated passenger to reach the top shelf at a grocery store.
Essentially, the iBOT is a gyro-balanced mobility device designed to operate either on four or two wheels, stabilizing
the user by automatically adjusting itself to compensate for any shift in weight.
This degree of sophistication does come at a price though, and at £16,000 ($30,000), it is only available to those with very deep pockets! To many Electric wheelchair users, the average price of a wheelchair will be around £3500 ($6500).
When choosing an electric wheelchair, be sure to use a reputable make from a licence supplier. This will ensure you receive full back up if the chair needs servicing. Also beware of second hand electric wheelchairs, as they can suffer from cracked frames, faulty batteries and worn out motors.
The way that Electric wheelchairs are propelled also varies, and these different methods give different characteristics to the wheelchairs. The following are the three basic methods of propulsion:
* Rear Wheel Drive Wheelchairs
This is the most common method of drive for an electric wheelchair. This method makes the wheelchair fast, but can give a poor turning capability when compared to front and mid wheel drive chairs.
* Mid Wheel Drive Wheelchairs
This method of drive gives the best turning capability of all the wheelchairs. The wheelchair can be a little unsteady when starting and stopping though, and may not be suitable for uneven surfaces.
* Front Wheel Drive Wheelchairs
This method of drive gives a lower top speed than rear wheel drive chairs, but offers a good turning capability.
Wheelchair Battery Types
There are also three different battery types to be aware of when choosing your wheelchair. These are "Wet", "Gel", and the newer "AGM (Absorbed Glass Mat)" types. Their properties are listed below:
Wet Batteries
Wet batteries use the chemical reaction between lead and sulphuric acid to create electrical energy. As the batteries need filling with distilled water, they do have a higher maintenance rate, but are lighter than Gel or AGM batteries.Wet batteries are also prone to leakage, something which is important if you intend to put your wheelchair in the hold of an aircraft.
* Positive Aspects
Cheaper.
Less vulnerable to overcharging.
Great performance with careful maintenance
Lighter per Ah compared to most Gel or AGM’s.
* Negative Aspects
Require maintenance.
Battery acid can leak, causing corrosion and damage to chair and wiring.
Not approved for airline travel.
High rate of self-discharge when left sitting (6-7% per month).
* Gel Batteries
Gel batteries contain a mixture of sulphuric acid, fumed silica, pure water, and phosphoric acid, which forms a thixotropic gel. As there is no liquid in the battery, they do not leak or require maintenance like wet batteries.
* Positive Aspects
No maintenance.
Cannot leak.
Operate better than wet batteries in low temperatures.
Less gas released when charging than wet batteries.
Approved for air travel.
Longer life cycle than wet batteries
* Negative Aspects
Expensive.
More weight per Ah than wet batteries.
Susceptible to overcharging.
AGM Batteries
AGM batteries have an absorbent glass mat sandwiched between the plates, saturated with acid electrolyte, but with none free to spill. This “sandwich” allows uniform distribution of the electrolyte over the plates, and reduces the chance of battery damage caused by vibration and jarring.
* Positive Aspects
No maintenance.
Can’t spill or leak.
Shock resistant.
Minimal gasses released when charging.
Low self-discharge rate (3% per month at 77’F).
Approved for air travel.
* Negative Aspects
Highest cost.
Susceptible to overcharging.
New technology.
When purchasing a new battery, shop around. Buying a new battery from a wheelchair supplier or medical supplier will cost more than an electrical supplier. Don't be taken in by bogus claims that the batteries can only be purchased from wheelchair suppliers.
