So how can I have a "sensible" ALL DAY LONG with GREAT RANGE, powerful, 15 mph powerchair? Its actually pretty easy!
Simple physics, higher voltage and lithium battery power.

If your existing powerchairs control system COULD accept 48 volts instead of its usual 24 volts (by having 4 batteries of half the size rather than your 2 big ones connected in series) your chairs torque, and its range at the same speed (6 mph) would not be affected. So you would get double the speed, and still have exactly the same slow speed performance without any torque or range loss.  Unfortunately it cant be done though - 48v will make much smoke come out of your control system!

IF it could use 48v (4 smaller half sized batteries) The controller could still deliver its maximum rated amps to the motors, (80A or 100A or whatever) and the battery current will now be exactly half its previous value since battery the voltage has doubled.  I could explain why that is but for now please trust me when I say its true!  (Simple terms -- Its because the controller uses a "pulse width" to control the max amps/volts to the motors.  So for all intents and purposes nothing has changed. At least as long as you stay below the 6mph. (other than slightly better efficiency).

Except that now the chair will actually go twice as fast at say 12 mph instead should you so wish!  Now that 12 mph speed will use slightly more power but not much.  But you have no loss of torque or range at the slower 6 mph. In fact you may gain some torque.

But at the low speeds we are talking about, it doesn't take much more power to go faster as long as the same motors/gearing are still used. And of course at twice the speed you get there in half the time. So just by doubling the voltage we can now have our cake and eat it!  I don't believe in a free lunch either. 

So what's really happening?  Simple! The controller and higher voltage are working together effectively as a reduction gearbox at the lower speeds. Huge efficiency gains for practically nothing.  So you get free extra speed! Sounds "wrong" but its not!  Its just simple physics.

Shame then, that the powerchair industry "sheep" have not figured this out. They are still stuck in the 24v lead acid "gel" battery slow lane.

So my new BM MK3 CHAIR, by taking a set of 8.5 mph motors (in my case from the existing "Groove" powerchair) and running them on a 43v 13 cell Lithium battery will be 15 MPH capable.

With a bigger Amp/volt controller - The Roboteq 150 Amp per channel (300 Amp 500A Peak) Controller.  Then I can have 8.5 mph multiplied by Two! On double the voltage. So almost double the speed of the Groove 8.5 mph motors it is using.

This works out at exactly 15.2 mph. With no range penalty at all even on the stock battery Watt Hour capacity, or torque penalty at the slower speeds. In fact there are some gains in efficiency as speed increases. And some more due to higher voltages.

But I want lots MORE torque than a stock 8.5 mph powerchair ever had!  Why? Because they are frankly useless! No problem though. The Roboteq and its very high Amp and double voltage capability will give me that in spades... Enough to plough a field or tow a truck.

And more range! No problem, the 3000 + watt hours in the Lithium battery will give me around DOUBLE to THREE TIMES the range of a set of standard heavy group 24 Gel batteries. And with 4 to 5 times the cycle life. I expect a 7 to 10 year MINIMUM battery life compared to the realistic 1 to 2 years I get now... 

And with just half the weight. I will say that again.  Half the weight!  That alone will improve climbing, range, off road ability. But they are not cheap! See the battery page. here Lithium battery

The manufacturers are really not trying as you can see. They get their money far too easily. 

TO BE UPDATED DURING BUILD regularly!

What's the purpose of the pages about the MK3 chair and the earlier MK1 and MK2 chairs since I don't sell them? To embarrass the manufacturers into getting with the show, and doing some real development work. And to show other wheelchair users especially Paraplegics like me, what is possible. As such there are others now doing the same or similar, many are members of my Message board.