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Asked — Edited

Motorized Wheelchair

Good Day!

I am in Southern Indiana, beginning a project using an Invacare M91 Heavy-duty Wheelchair, I purchased off Craigslist. The wheelchair was manufactured in April 2004 and has an advertised weight limit of 400 pounds

The batteries were working but shot ... two 12 volt lead acid batteries (half a million pounds each) that I have converted to 7s2p 18650 Lithium Batteries salvaged from laptop batteries that gives me just under 30 volts @ 5400 mAh. I will eventually make a 7s10p 27000 mAh (27Ah)or maybe 7s20p 54 Ah matching the original 24volt and 50 Ah ... depending on battery availability.

The seat is removable so that will eliminate an additional million pounds of resistance.

This past Memorial Day weekend my team and I 'refurbished' the front and rear casters and the Mid-Drive motors by removing, cleaning the hair, carpet fibers, and dust from the bearings. This will alleviate a tremendous amount of resistance for the motors.

I think I have the controller particulars down the joystick is a MKV SPJ 80 that is connected to the controller via mini sub 15 pin connector ... my research shows it is an inductive connector ... the pinout is (according to : http://www.invacare.com/doc_files/1114808.pdf):
1 +15v Switched
2 +15v
3 N.C.
4 Serial Data 1
5 N.C.
6 Common B-
7 N.C.
8 N.C.
9 N.C.
10 Serial Data 2
11 Common (B-)
12 Common (B-)
13 B+ PTO (Charger Input)
14 B+ PTO (Charger Input)
15 Charger Inhibit/Serial Programmer
Further, some have posted that when the joystick is at TDC the voltage is 2.5 Volts on both data channels, forward is 5.0 volts, and reverse is 0.0 volts.

Will the EZ B V4 be able to help me out?

Can any of you help me with using the EZ B with my intentions?

Is this possible?

What is the meaning of life?

Do chickens really need to cross the road?


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Forget trying to hack the controller.... People have tried with limited success. The best way is to ditch the controller and joystick altogether and use a sabertooth 2 x 25 or 2 x 60 motor controller with the ezb4 to control your wheel chair base... Much simpler and works fantastic... If you still need joystick control, well the ezb4 has you covered there as well... The ARC has a joystick control that works with inexpensive joysticks you can get off of eBay...
I have read about this wonder of modern circuitry ... In education there is a limited budget ... right now, the sabertooth is outside my means.

is there a used market for the sabertooth?

Thanks for the response
The ezb4 can easily read analog voltages... So if you can read the analog voltages from the joystick then you might get basic "tank style" control... however basic means left, right, forward, reverse... Speed control will be another matter... Not sure how you would get that...