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Explain how the battery in this works and how its all connected.  Motor as well please.   Prismatic Cell battery

Posted on 2013-06-23
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Last Modified: 2013-06-24
Watch the video    http://youtu.be/bJoUaaHgomI?t=3m6s      Thank you!
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Question by:Ryano360
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Expert Comment

by:Ray Paseur
ID: 39269440
It's a Lithium Ion Battery according to the speaker.  That would appear to be a mixed blessing.  The LIB has lower weight and carries a greater charge, but one of the advantages of Lead-Acid batteries is the greater weight -- it provides a lower center of gravity.

See http://www.youtube.com/watch?v=3IVj44t49T4

What is the PHP component of your question?
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kode99 earned 2000 total points
ID: 39270387
Equivalent lead acid batteries are around 5 times heavier for the same amount of power.  While it certainly does help with the stability with the lower center of gravity,  the overall weight of the big chairs with lead acid batteries makes them pretty unwieldy for transport.  

Also because the big power chairs have much more functionality (lifts etc.) the overall weight is quite high.   So proportionally the heavy lead acid batteries are less of the total weight of the vehicle, er chair than in a compact chair like in the video.

I sort of laughed at the point where he jumps out of the chair and picks it up over the curb,  like it would be easy to do that if you actually needed the wheelchair.  Though it actually looks easier to manage than a standard non powered wheel chair for putting in a car.

A prismatic battery is a reference to the style of lithium battery.  More or less means it is a flat design instead of a cylindrical design with a hard external enclosure.  I'm sure you can google to get lots of pictures,  the guts of the batteries are laid out in flat sheets.  This is fairly typical for a cell phone batteries.  It's more expensive style than using a bank of cylindrical cells but may have been necessary to get the approvals for air travel and also would have  allowed them to keep it as compact as possible.

The controls are fairly simple.  The joystick and speed control hooks into the central
black box they showed which then connects to each of the two rear wheel DC motors.  The unit has a overall throttle or speed control then the joystick will independently adjust the speeds on the rear wheels in order to steer the chair.

So stick left would adjust the left wheel speed down and maybe right wheel speed up to turn the unit left,  stick left is the reverse.  Likely the central control also has safeties built in to avoid tipping the chair while cornering at any speed.  I would not be surprised if the chair can be calibrated for the weight of the user as well.

The motor speed is controlled by adjusting the voltage to the motor.  So when steering there will be a difference between the voltage at each rear wheel motor.  I would expect the motor is not directly connected to the wheel but has some gears to increase the torque to the wheel.  I would probably be surprising how small the motor on the wheel assembly actually is.

Likely the lightweight frame and the lithium batteries are a big part of the price tag on this.  The controller is likely fairly standard.
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by:Ray Paseur
ID: 39271325
@kode99: +1 for a really good answer!
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Author Comment

by:Ryano360
ID: 39271736
@kode99: Thank you very much, helpful indeed. I'm working on building a wheelchair of my own. I also found it funny when he got out of the chair and lifted it over the curb.
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Expert Comment

by:kode99
ID: 39273698
Check this out for a really fun hub motor use,

http://www.youtube.com/watch?v=USTOxlv_7m0

Aside from the very cool bike his use of recycled rechargeable is interesting.  

Also check out Golden Motors,
http://www.goldenmotor.com/

and go the to the e-wheelchair link.

Looks like the same wheelchair from your video with some modifications.  They also have the controller as a separate part as well as a variety of hub motor wheels for different applications.  Some of the designs for cycling may offer some nice alternatives for wheelchair applications.

Here's how simple a electric conversion for a standard wheelchair can be,

http://www.youtube.com/watch?v=6P1C-GdOohs

Not sure how to get my hands on
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