Wheelchair build , Hello and VR2 question

[nick]

Hello all
we are Meg and Nick
We are building/modifying a wheelchair after discovering John's fantastic web site
This is how it was when it arrived . It is a cheap Chinese wheelchair from ebay and is brand new


This is after some modifications shown next to my wifes Vessa traveller . The Vessa is 18 years old and is now pretty sad but it was a fantastic chair and really well made
It used to take my wife with one child on her lap and the other standing on the back on the pegs next to the wheely bars


This is how it is now




There is more work to be done
The arms are being replaced
and tomorrow I should get the big tyres and wheels
The wheels will need the bearings cutting out and a plate made up
We are also waiting on the new LiFePo4 batteries . At the moment it is running on the 24v 20ah lifepo4 pack we fitted to her Vessa about 18 months ago
The new battery will be built by me this time from 3 ebike 9ah packs with charges and BMS into one 27ah pack
These new battery packs are built from A123 cells which are the ducks guts and can deliver current almost as well as the little Lithium Ion cells used in RC planes and Helicopters

There are some other things to be sorted as well such as the Castor that has been introduced to the front wheels since shortening the wheel base
We will see how that is when the new wheels and tyres are fitted
I may have to cut the tubes off that the front wheels mount in and re weld them perfectly vertically

I do have a question as well
Does anyone know where I can buy the PC software for the P&G VR2 controller?
I have not tried the local Australian distributor yet but I think I know what there answer will be already
well thats it for now as its late down under but there is more to come
But I would like to talk some next time on the findings of how the chair responds with different people in it now we have shortened the wheel base and moved the seat further back
My wife and daughters are within a 2 kilos of each other but due to my daughters height (they are taller) it is a vastly different beast

Nick

[Burgerman]

Interesting. Will be interesting to see about range with such small batteries? Whats its speed?

You need a pp1b or OEM p and g programmer. Or equivelent PC software. Getting them to sell you this is the hard part.

Dont nuy any easy to get dealer or end user or pp1a programmer though as they are a waste of space!

I have considered lithium phospate myself but with up to 240 amps draw, and 8mph so a requirement of 70 or 100 ah just to equal the lead acid and double that to make real sense cost is too prohibitive...

[nick]

Hi
With the weight reduction due to the lifepo4 batteries and the fact that these batteries have zero or almost zero Peukert effect, the 20 ah cell is basically the same as a 80 ah lead battery.
The old batteries (AGM,s) weighed 38 Kilograms.
The new lifepo4 battery weighs just under 10 kilos
So we chopped 28- 29 Kilograms out of the chair.
This made the chair a much better chair all round and of course increased its range.
It also extended the life of the chair as it was getting pretty long in the tooth when we fitted the new battery
and the weight reduction meant the wheels lasted longer than they otherwise would have.
We used to get a full days use with the Sonnenschein 40 ah batteries but with the lifepo4 20Ah battery we can get 2 days use off the one charge
My wife has actually used it for 3 days a few times before recharging, although this was with slightly ligher use
The fact that these batteries have almost zero Peukert effect is the other reason why the 20Ah lifepo4 outperforms the 40ah lead gel cell
These batteries will provide 20 amps for a full hour or 40 amps for a half hour or 60 amps for a full 20 minutes , something you cannot get with a lead based battery due to the
Peukert effect. Depending on the brand of battery the peukert effect can be quite high and have a big effect on how long a charge lasts

Nick

[Burgerman]

I realise all of that but I want to go twice as fast that means 4x the energy needed. so 8 or 12 mph becomes practical even off road. And I want more range. So instead of making the battery smaller and lighter I need to cram as many in as humanly possible just as we do now with pb batteries. Then instead of getting similar performance from a smaller battery we get huge performance and range increases!

Why have empty space on board when that can be used up by adding batteries/power which translates into speed and range or fat tyres? I hate waste! Taken to extremes that would mean a powerchair with a battery the size of a matchbox. That would work but it will still perform as it does now plus a small bit for some weight reduction. What we should do is FILL it with those batteries and have 30mph 1 week performance!

[JoeC]

I have looked at the A123 cells in the past, and the math says that a pack built with 8 series and 12 parallel ought to have a resistance on the order of 5 milliohms- about the same as a new set of Odyssey PC1500 in series. The cells are rated for 70 A continuous, 120 for 10 seconds, so a 1440 amp burst is well within such a pack's comfort zone. The allowed charging rate is 10A per cell, 120A for the pack. The best price I've seen on the cells would put this pack's cost in the $650 range, but the cells are rated for 1,000+ cycles at 100% DOD. Not bad for a 15 pound pack!

20 AH would probably give adequate performance, if not range, for someone Burgerman's size. For someone significantly smaller, I can see how this pack would be absurdly better than a pair of group 24 batteries. Less nameplate capacity, but 90 pounds of weight reduction from the batteries.

Can you tell that I'm interested?

[Burgerman]

And a correct charge voltage is 28.8v for 8 cels. So a stock cc cv 28.8v wheelchair charger will charge them. But to gain some real benefit you need to double the AH though since you actually ca fit it.

For easy upgrade what we all need is 48v 100 amp controllers... Then we can double the speed and capacity in one easy go on any wheelchair with the same motors

[JoeC]

Unfortunately, ever since the Therac 25, it has been hell to get any medical device approved:

http://www.ccnr.org/fatal_dose.html

I can tell you from first hand experience that working on an FDA regulated medical device is a soul sucking experience- more than half your day is paperwork, and countless meetings and committees prevent you from getting anything done when you should be designing something. If any change is made, it must be either exhaustively tested to failure, or it must be very convincingly argued that it's physically impossible for the change to cause any new danger or possibility of injury that was not present before.

I agree 100% that a higher voltage motor will improve chair performance in every measurable way, but it will be an epic struggle to get it through certification. The companies had no choice but to do it the first time, other than to close shop and stop making chairs. Now they only make small incremental changes, and although they claim publicly that their new chairs are different and better than ever, their goal when they speak to the regulators is to emphasize that almost nothing has changed.

[Burgerman]

But that only applies to the US and thats 15 percent of the worlds population.



The rest of the world dont move on either!

[pattherat]

Hi Nick, The VR2 OEM Progamming software part number is D50145 MOB.PCP B - OEM (W'CHAIR & SCOOTER). Price is $230.00. Email me if you want to talk further about it: pattherat@earthlink.net . I like what you are doing, I've seen that chair and have thought of modifying it also. Im also interested in the LiFePo4s. Some of the pictures you posted aren't showing up for me, could you repost them and pics of the battery packs?

[Burgerman]

The battery packs are just the "ping batteries" type lithium polymer ones that we have been discussing elsewhere for months. They are available as A123 ort Lithium ion phosphate, etc. There are many places to buy e bike packs. I have some A123 cells here. They are used by us model plane/heli people as a "safe" alternative to lithium polymer.

Basically these http://shop.ebay.co.uk/i.html?_nkw=a123 ... m270.l1313

But there are electric bike specialists springing up all over with 12, 24, 36, 48v packs ready to go. (like ping batteries) http://www.pingbattery.com/servlet/StoreFront
Check specs though. Many are not high enough C rating for heavy use and dont actually have the capacity it says on the tin... Although these seem good.

The hyperion charger I use for everything can charge them and balance them as well as measure true capacity. http://www.wheelchairdriver.com/hyperion.htm
But only up to 7 cells. So you need to charge them in groups of 4 cells like I do with lead acid batteries to get your 8 cell 28.8v pack.

For real gains you need as much battery on board as possible. That works out a lot expensive or I would have done this already. But the C rating gets less important the more of them you have of course!

8 OF THESE WOULD BE PERFECT FOR MY FAST FULL POWER MODDED 20MPH POWERCHAIR, AT HIGH COST... http://cgi.ebay.co.uk/24V-20AH-LiFePO4- ... 3f017094a8

If you fit smaller capacity then you need higher C rating than this, But at about 1200 pounds UK this would allow high speed AND tons of range. And if used as 48v (subject to suitable controller being found) would allow that speed (16mph from 8mph powerchair motors.

[Burgerman]

Have a browse. These sort of packs are common now. http://shop.ebay.co.uk/i.html?_trkparms ... .m14.l1514

[nick]

Hi John
Im guessing your more of a Blower Bentley man than a Bugatti man

"So instead of making the battery smaller and lighter I need to cram as many in as humanly possible just as we do now with pb batteries. Then instead of getting similar performance from a smaller battery we get huge performance and range increases"

[Burgerman]

Cant stand to see wasted space! My Suzuki GSX1100 Had a huge T4 turbo, and two stages of nitrous injection... There was room. Had 280bhp before the nitrous at the rear wheel You dont HAVE to use it but its there if you want it!

Seems daft to spend all that on battery technology and not get as much extra performance as possible...

[nick]

Well following the saying
Adding lightness adds speed ( well range in this case)
I have done some work on the chair
this is how it was
[img]http://www.flickr.com/photos/9866329@N07/4870954135[/img]
[img]http://www.flickr.com/photos/9866329@N07/4870953789[/img]

But I have pulled it apart
[img]http://www.flickr.com/photos/9866329@N07/4871564702[/img]
[img]http://www.flickr.com/photos/9866329@N07/4870955515[/img]
[img]http://www.flickr.com/photos/9866329@N07/4871565990[/img]

And added some lightness
[img]http://www.flickr.com/photos/9866329@N07/4870958015[/img]
[img]http://www.flickr.com/photos/9866329@N07/4871567666[/img]
[img]http://www.flickr.com/photos/9866329@N07/4870957351[/img]
[img]http://www.flickr.com/photos/9866329@N07/4870957095[/img]

It weighed 7.6 Kg and now weights 6.3 but since drowning it in half a can of Zinc it is now 6.5 Kg
That Zinc paint is really heavy!

There were a few sacrifices to the God of Speed (well lightness actually)
[img]http://www.flickr.com/photos/9866329@N07/4872001340[/img]
[img]http://www.flickr.com/photos/9866329@N07/4871392499[/img]
[img]http://www.flickr.com/photos/9866329@N07/4871390751[/img]
but a new one of these
[img]http://www.flickr.com/photos/9866329@N07/4871393015[/img]
And this
[img]http://www.flickr.com/photos/9866329@N07/4871391939[/img]

That credit card must think its in training for the Olympics!

We got the new wheels and Tire's the other day and have taken a motor and wheel around to a local pulley company to have a flange and drive ring made up
I thought they were just a pulley company and was going to adapt a pulley as John had done
But turns out they can make me a complete hub/flange
The pulley idea is a great idea and one I would have never thought of till I saw it on John's site
The tyres are good as they are actually a 6 ply and synthetic enhanced which I presume means silica
But the wheels are not flat in the centre , bit are domed
These are the only ones I could get so the idea of cutting out the centre and mounting them like John has ,has gone out the window
The pullley shop is going to make me a steel disk that I will push to the bottom of that big axle type part sticking out of the wheel
I will then spot weld with the Mig the inner circle to that stub axle and then trim the axle down
Like this but a disk
[img]http://www.gokartgalaxy.com/images/steelwheels.jpg[/img]

New Wheels and tyres
[img]http://www.flickr.com/photos/9866329@N07/4871569574[/img]
[img]http://www.flickr.com/photos/9866329@N07/4870960605[/img]
[img]http://www.flickr.com/photos/9866329@N07/4870959961[/img]

well thats it for now
the new batteries and VR software should turn up this week so thats is a bit exciting

Nick

[TwoTeasChris]

ADMIN: This post is the same as Nick's above with img tags changed to url. Might want to paste this over that.


Well following the saying
Adding lightness adds speed ( well range in this case)
I have done some work on the chair
this is how it was
http://www.flickr.com/photos/9866329@N07/4870954135
http://www.flickr.com/photos/9866329@N07/4870953789

But I have pulled it apart
http://www.flickr.com/photos/9866329@N07/4871564702
http://www.flickr.com/photos/9866329@N07/4870955515
http://www.flickr.com/photos/9866329@N07/4871565990

And added some lightness
http://www.flickr.com/photos/9866329@N07/4870958015
http://www.flickr.com/photos/9866329@N07/4871567666
http://www.flickr.com/photos/9866329@N07/4870957351
http://www.flickr.com/photos/9866329@N07/4870957095

It weighed 7.6 Kg and now weights 6.3 but since drowning it in half a can of Zinc it is now 6.5 Kg
That Zinc paint is really heavy!

There were a few sacrifices to the God of Speed (well lightness actually)
http://www.flickr.com/photos/9866329@N07/4872001340
http://www.flickr.com/photos/9866329@N07/4871392499
http://www.flickr.com/photos/9866329@N07/4871390751
but a new one of these
http://www.flickr.com/photos/9866329@N07/4871393015
And this
http://www.flickr.com/photos/9866329@N07/4871391939

That credit card must think its in training for the Olympics!

We got the new wheels and Tire's the other day and have taken a motor and wheel around to a local pulley company to have a flange and drive ring made up
I thought they were just a pulley company and was going to adapt a pulley as John had done
But turns out they can make me a complete hub/flange
The pulley idea is a great idea and one I would have never thought of till I saw it on John's site
The tyres are good as they are actually a 6 ply and synthetic enhanced which I presume means silica
But the wheels are not flat in the centre , bit are domed
These are the only ones I could get so the idea of cutting out the centre and mounting them like John has ,has gone out the window
The pullley shop is going to make me a steel disk that I will push to the bottom of that big axle type part sticking out of the wheel
I will then spot weld with the Mig the inner circle to that stub axle and then trim the axle down
Like this but a disk
http://www.gokartgalaxy.com/images/steelwheels.jpg

New Wheels and tyres
http://www.flickr.com/photos/9866329@N07/4871569574
http://www.flickr.com/photos/9866329@N07/4870960605
http://www.flickr.com/photos/9866329@N07/4870959961

well thats it for now
the new batteries and VR software should turn up this week so thats is a bit exciting

Nick

[Burgerman]

I think its pretty easy to follow as it now is. Thanks for fixing. Wonder why it did not work? AnywayI will leave it as it shows what to do if it doesent work...

All that work to lose a few pounds looks like a very difficult exercise! And the wheeld / tyres? What sizes and what logic behind them? Would be interesting to know why you chose what you did.