He was using a Stock Invacare Arrow and competing in some strange mileage marathon for Powerchairs. He was regularly getting 90km+ (about 40+ real world miles).
For those that occasionally
need a big day out, it works like this:
He bought a 24v Lithium Phosphate battery (actually several) from Ping batteries cheaply and connected them in parallel to make a laptop shaped pack of either 2, 3 or 4 batteries.
My page with link to Ping here http://www.wheelchairdriver.com/lithium ... rchair.htm No they are not affiliate links!
He made them into a flat pack like a "fat laptop", and taped them together with silver duct tape along with two loops. One loop each side to slide over the handles of the backrest. It just hangs from there like a backpack on his chair with a 24v cable coming off it.
The wires are all connected together in parallel. So the thing is still 24v. Amazingly these cells can be charged using the standard wheelchair charger. (peak voltage 28.8 max) safely. But not at the same time as the standard wheelchair Gel Group 24 ones he was using, (2x 73ah MK) He did them separately. Because of internal resistance and other differences.
If you don't understand things like
"parallel" and how to fit plugs and sockets then you
need an enthusiastic car electrical guy or similar to
wire it up for you! But its a really simple thing
Now the discharge rate/voltages are not the same for each battery type. So don't just go connecting them up in parallel with your wheelchair batteries willy nilly! You COULD and with them all fully charged no damage will occur, but one set will waste energy trying to charge the others so you will not benefit as much as you should as power gets wasted...