Mobility Skootin.

[Drunkskunk]

So i bought an electric wheelchair for a project I have in mind. it has 2 large motors, but no real torque or speed. So I was thinking a few extra volts might help.

So how much voltage can these stock controllers handle? it's a 24 volt system. I want to try 36 volts. anyone ever try this?

 

[amberwolf]

AFAIK they all have protection to only work within the range of the batteries they come with.

But you can verify that, if you have an adjustable power supply, by running it at about 28v (full charge of SLA), then while wheels off ground (so it doens't overload the psu), try the throttle gently, see if it moves wheels. If so, then increase voltage by a volt, and retry. Keep doing that until it won't move the wheels, or until you are satisfied that it will run at the voltage you'd like, or until it smokes.




So if they're meant for 24v SLA, then the max is probably 29V, and min is probably 22V or more. (might work down to 20).

They may have other limitations, like very low speed limits (4-5mph, maybe up to 8mph, is common).

I played with a couple of controllers I'd gotten for powerchairs, and couldn't get them to run motors if they were above the 29V limit. Might've been 30V on one. I think one of them was from a quickie chair, the other I don't rememeber. I doubt I still have either one. I have the remnants of another powerchair controller, scooter type, but I know it doesnt' work after the corrosion and heat from the fire and chemicals used to put it out.

I've been told by a service guy that a number of controllers are programmable, but unless you're a service center for that brand you'll never get the stuff to do it with.

The motors themselves, however, should run on whatever you want to try.

I used various powerchair brushed motors on CB2 at 36v, and then at 48v, and they had enough torque even with a tiny 4QD 4fet controller to destroy numerous chains, rings, even a whole wheel once, due to bending the frame with the torque and causing derailments. :/

Iv'e got a brushless one that runs fine on an ebike controller after adding halls to it; there's a thread about it somewhere. I think I ran it at 36v, I forget, but it was made for 24v system. Didn't hae the controller that it was used iwth so dunno if that had any limits.

 

[Drunkskunk]

Thanks. That saves me from ordering 3 batteries.

 

[nutnspecial]

I recently ran a little 200w scooter on 48v instead of it's stock 24 to no ill effect, other than that making the gearing too tall for how much power the motor/controller/wiring safely runs with.

Do you have any power supplies / chargers? That would be a good way to test.

 

[Drunkskunk]

I ended up buying 24v worth of battery, found the motors work great, then proceeded to carefully plan out a frame jig and frame for a powered cart.

Then My friend and I got drunk.
Very drunk.
And then this happened:

It's a hoot. 3mph. climbs my road with the weight of me plus a cooler and the girlfriend in the garden trailer. So embarrassingly redneck that it's a new kind of awesome.

But it's not what I planned to do with this thing. My father had a stroke and lost his sense of balance. He insists on trying to walk with a cane, but he can't get far that way. and he absolutely refuses to even consider the possibility of a wheelchair. I've tried to convince him to just give one a try, but he refuses. Oddly, he loves the carts at walmart and uses them without a problem. Somehow a walmart shopping scooter is dignified, but a mobility scooter isn't....

So I decided to build one in disguise. I had planned to add the motors and the scooter front wheel to a frame that would hold the deck of an electric lawn mower. I'd then call it an electric riding lawn mower, and let him park it. My house has no front gate at the moment. I have to walk a mower around the block to get from the front to the back yard. I'm hoping that the trip on a scooter mower would be enough to let him experience the freedom of a scooter chair. I think if he gets out and can go around the block, he'll give up his objections and get a mobility scooter.


Right now I still have one snag. the joystick control for this thing isn't as straight forward as I had hoped. I need to modify it to a simple forward/reverse button/switch/throttle. But the box is full of chips and more than a dozen wires. At the shack I'm building this at in secret, I don't have the tools to trace out what the circuit is doing. So anyone have any idea how these wheelchair joysticks work?

 

[Voltron]

Nice! All you need is some more walnut and brass and he'll have a streampunk special. My dad just joined the fell down and cracked his pelvis club, so coming up with mobility options is in my future too.

And if that's still not redneck awesome enough for him, maybe something like one of these

 

[amberwolf]

So anyone have any idea how these wheelchair joysticks work?

If it's the original powerchair stuff, then there are a couple of ways they work.

One uses two potentiometers, just like the old analog joysticks for PCs and game consoles. One is X axis, one is Y. Both are fed into the controller, which converts that into motor directoin and speed control inputs. How exactly it does it is different with different ones, but you could separate the X and Y axes by using two separate potentiometers, however it will make it more complicated to use, not less.

You could even completely redo the way the inputs work by using "digital potentiometer" chips to replace the x and y pots, and then creating your own buttons, sliders, or whatever you wanted to select forward, reverse, sideways, speed, etc., and having an arduino or other MCU convert those into commands to the two digipot chips.


Some use four switches and a separate throttle pot (or other method of setting the speed), whihc you could more easily reconfigure with external switches wired in parallel with them for left, right, forward, reverse, etc. (or even just remove the joystick mechanics that press down on the switches and add buttons over the top of them). This type would simply apply the pre-set speed to whatever direction was set by the switches pressed upon by the joystick mechanics.


Some may use other control input technologies I havent' seen, but they probably still work in general like one of the two above.



In general, though, the joystick is probably the simplest input method for controlling the direction of the vehicle, short of putting a steering wheel or handlebars on it that either mechanically steer it, or operate the steering potentiometers or switches, and an accelerator pedal or hand throttle for speed control.

 

[Drunkskunk]

So this project is growing a little bit. The girlfriend wasn't as fond of the redneck Chair-iot as I was, and there was no way my dad would ever use it, so I started plans for a new frame. And then found this thing.

Only 1 steering wheel is connected by design, and at a steering ratio that would be impossible for anyone who can't bench press their own weight. Only 1 chain has a freewheel, the other is bolted to the axle. And the brake is a friction bar that presses the tire. it needs work.

But... I've got a hack saw, a welder, 2 wheelchair motors, and 2 large 12v batteries with no home....