"The First Solar Powered Electric Wheel Chair"
By: Michael Swift, Chris Johnson, and Dr. Pecen; 1999-2000
An electric wheelchair is limited in range by two 12V batteries. These batteries have to be charged by plugging the batteries into a charger and using AC wall power when they are drained. The need for AC wall power dramatically limits a disabled person ability to move to far from areas without AC power and the charger.
Our project goals start with mounting a solar panel above the seated occupant to absorb sunlight and outputting DC voltage. The solar panel weighs about 25lbs, stability must be maintained to achieve a safe vehicle. The DC voltage will be used to charge the wheel chair batteries for extended range. Finally, minimal input from the occupant is a goal so that it is easy to use.
All of the goals as outlined were achieved. The panel was mounted, stability maintained, and the batteries can charge by sitting in the sun without the need for AC wall power and the charger. If the batteries were completely dead, it would take approximately 12 hours to fully recharge the batteries under ideal sunny conditions. Giving an exact figure on the extended mobile range is very difficult because of the unknown variables. The current draw from the batteries will never be same due to varying motor loads and speeds. For any given situation, knowing exactly how much current is being used per how much current is being put back into the batteries will never be the same. There will however, be a noticeable increase in range for the occupant, more for some, less for others, depending on their usage characteristics.