Like all small electric cars its ultimately a bit pointless. Doesn't work indoors properly miles too big. It will likely get wheelchair users tarred with the same brush and then we will not be welcome in pubs, shops etc.
So really isn't a wheelchair and doesn't work properly indoors.
Requires you to transport it to wherever you want to use it off road as it will have run out of steam by the time it arrives anywhere. Requires that you then swap one chair for another (transfer) after towing it or transporting it in a vehicle you can drive from a proper wheelchair. Or if you did drive it to the venue where you needed it, a couple of hours "off road" means you definitely wont get home again. Of course if you live on a farm it has its place. In which case lithium would improve it. Slightly.
And silly money. There are massively better and very quiet, much cheaper petrol versions around that work way better outdoors, with far more range, speed and less weight. Everything for the disabled doesn't need to be lumbered with batteries, slow speeds, and dozens of zeros...
There are thousands of such electric off road "wheelchairs" made. All much the same. Mostly because it seems like a licence to steal your wallet just because its battery powered.
All of them perform worse, cost more than say something like this at £3550 or 5k us dollars:
http://www.ebay.com.au/itm/ATOMIK-ATX-4 ... 360wt_1124Twist and go, quiet, electric start, 4x4, no foot pedals needed. 55kph and more see spec. That makes "off road wheelchairs" look silly. There are smaller, slower, single cylinder ones, for HALF of this price.
More...
https://www.google.co.uk/search?q=off+r ... 97&bih=432https://www.google.co.uk/search?q=golf+ ... 97&bih=825https://www.google.co.uk/search?q=quad+ ... 97&bih=432