More powerchair controllers and motors and Lithium Batteries

[Burgerman]

http://www.chinafreepower.com/product_show.asp?id=97
no prices... L;ots of stuff!

http://evcomponents.com/cscart/index.ph ... ory_id=171
Look around lots of useful gear! And prices...

These both advertise on my site. I might be able to go 36 or 48 or some other big figure after all! Keep same motors and torture them! With no loss of range. Taking a good look later when back.

[JoeC]

Wow- that second site, it's what we've been waiting for. 900 amps rated current from a 25 pound 12v battery- only $440. A pair of those would take 50 pounds out of your chair!

Also exciting is the 40AH battery, 300 amps at just over 13 pounds, very attractive for a "fold up and put in the trunk of a taxi" chair that can actually move under its own power. It's just too bad they're illegal to bring on a commercial passenger flight.

[Burgerman]

Nominal Voltage: 3.2 .
Amp/Hour Rating: 100 .
Max Discharge Rating Continues: 3c (300amps) .
Max Discharge Rating Burst: 20c (2000amps) .
Max/Min Voltage Range: 2.5 - 4.25 .
Weight: 3.5kg (7.72 lbs) .
Dimensions: H 220mm(8.66") W 179mm(7.04") T 62mm(2.44") .
Recommended Charged Voltage: 3.8 .
Recommended Discharge Cutoff: 2.5 .
Cycle Life: >3000 at 80%DOD .
Cycle Life: >5000 at 70%DOD .
Operational Temperature Range: -45degC thru 85degC

7 OF THESE stacked in series will be 29.4v after charging at 4.2v per cel. (fine for the AGM charger at a correct 29.4 - 24v Lead acid chargers work on these cells as they need CC/CV)

Will give a true 100 amp hours plus and leave half the battery box empty... This size will go in the space a group 24 needs. ONE group 24.

Stood vertically they are the same height minus 5mm...
They are 4mm wider. Shouldnt matter.
They are 62mm thick. x4. = 248mm = same as a group 24. Or your Optima but 20mm taller.
That means theres room for two "stacks" exactly. But the second stack needs only 3 cels. So you can fit a true 100 ah in the space we now fit 70 or 55. And they can produce many thousands of amps!

NOW 20mph and 300 amp controllers are easily possible. The batteries exist and are available. So how much IS 16 of those...

Not cheap! eek. But notice cycle life... Should last ten times as long. Since we now have 100 amp hours and so will dischgarge them less deeply too. (speed not withstanding)

Now... I could just go 48 volts instead (series them and use more smaller cells) and use the same motors that I use for 6mph and get 12 easily. Just need a 48v controller!

Might just go for it and try it out. Where can I get a bigger volt controller? I wonder if you could run 2 powerchair controllers, one on each 12v pack and series the output... Phone call in the morning! At 48v 100 amps would be enough. Twice the power. Double the motor power and speed.

[James]

Hi guys,
I saw you posting links to our website about the Headway and ThunderSky cells.
Thanks for the kind comments.

Check out our forum for more info. We just launched it for more EV and battery discussion.

http://www.evcomponents.com/forum

Thanks,
James Morrison
http://www.evcomponents.com

[Burgerman]

Hes on the ball too!

[JoeC]

Hi James, glad to see you over here, and glad to see you're doing business in this kind of battery!

Do you have any further information regarding flying with these batteries? I'd love to put some of these in my wife's chair, but the best interpretation of FAA regulations that I've found is that a device can have a lithium battery totaling no more than 300 watt-hours, regardless of chemistry or construction. Do you know of any exceptions or ways around this?

Thanks!

[JoeC]

Thought this one was worth mentioning, can't believe I never saw it before:

http://www.pgdt.com/pdf/access.pdf

True dual 120 amps, but only 32 volts. Not intended for wheelchairs, but still appears to be built to a high standard of safety. Also not sure about the programming, but wow! Lots of current!

[Burgerman]

Phone call on monday!!!

I want. Why havent I seen this before?

Unless its the same as the R-Net with its 2 120 amp channels but not at the same time...

I also want to discuss running two 120 R-nets in series with 4 batteries and 48v... Because instead of the two 110 amp odyssey ones I could fit 4x 50 amp ones. Because if its possible thats a lot of power and 12mph from existing motors if they dont explode!

Will post the results of my call...

[Burgerman]

Spoke to the tech guys at P and G by phone for 30 mins...

They claim after lots of discussion that a Pilot Plus 100 as well as R-Net 120 will both do 100 and 120 amps per channel independently...

They then called back to confirm they were right after yet more discussions.

Which is untrue! As far as I can tell. I tested it with 4 batteries (2 series, 2 parallel) and drove it into a wall with all temperature and timed foldback turned off... It does around half power to each motor and 100 or 120 TOTAL amps...
And the Platform Controller has the same internals (different software) as the R-Net 120...

Dynamic claim the same thing.

I need to test a dynamic DX2 controller against a r-nET 120 on the bench.

Strangely I was told that it DOES split its 100 / 120 amps the last time I called them with the same question!

It MAY be that the cable and battery resistance is causing the voltage to fall and then the controller limits the power.

More testing needed.

[CPguy]

Apparently they are closing down, you may want to strike a bargain. http://evcomponents.com/

[JoeC]

I saw a couple of forum threads elsewhere that say that this shutdown is not going smoothly. I wouldn't risk my money there right now, unless I heard otherwise or had some very good assurances.

[JoeC]

Another company to look at for controller- Curtis Instruments:

http://curtisinstruments.com/index.cfm? ... y&catID=10

I just got off the phone with a sales/tech person, and they assured me that their 75 amp module absolutely CAN deliver 75 amps to both motors at once, which should provide solid competition to the Dynamic DX range as well as P&G. He also claimed that he thought their acceleration ramps could be set as short as 0.1 seconds, better than Dynamic and better than P&G gear will do with what they'll sell you. From what I've read so far, their OEM PC programmer is common to the powerchairs, golf carts, and electric vehicle parts. This means you would be able to buy it from a golf cart or EV conversion place without much hassle.

I don't know about the powerchair efficiencies or voltages, but I saw that they have some 200+ amp single channel controls that are rated for higher voltages. The prices I've seen (ebay, etc) look very competitive. I see some 36 volt 400 amp controllers available for $150 each:

http://shop.ebay.com/?_from=R40&_trksid ... Categories

They're intended for EV use, so I trust their failure modes, vibration resistance, durability, etc, a bit more than I trust the robot combat stuff. If you like massive overkill, this is the way to go. The only catch is that you need to manage processing of the joystick signal to two properly conditioned outputs.

[Burgerman]

Link on desktop for some reasearch! What do I need for say 36v capability and 200 amp per channel??? Must be something there!

[JoeC]

They have all the way up to 800 amp at 48 volt if you want it! The main problem will be in mixing channels. Could you set up a Pilot+ system to drive a pair of high power resistor networks? If they added to 50 ohms for each channel, you would be using less power on this than in energizing parking brakes. If it was set up properly you would have a trustworthy way of generating control voltages for your desired drive dynamics.

Maybe you have a better way of doing this? It occurs to me that if something like I described was wired improperly, it might not be very safe.

[Burgerman]

Well you can do that with a roboteq or a couple of floor cleaner or scooter controllers. But I was hoping for a "cleaner" method, which was simple. The resistor network thing works. But its a bit rough. Resistors heat up and you lose centering accuraccy etc.

[JoeC]

Sorry, on further reading it seems that some of the larger controllers are not for permanent magnet motors. Some of the sep-ex controllers are dual channel to an extent, but nothing quite as integrated as we'd like.

Regardless, the enAble40 system with the 75 amp output looks like a worthy contender. Once I try some more serious programming of the Pilot+, I will let you know if we're ever able to get more than 80 amps total out of the 80 amp module. If it really IS limited to 80 total (or 100 total for the 100 etc), then I will maintain my position that the DX2 at 2x120 amps is the strongest you can get for a neatly integrated powerchair.

I have also heard that the new generation of Roboteq will be coming with a much improved ability to be controlled with the analog input. By this I mean a finer graduation between levels of ramp rates, and a larger number of exponential curves available for the stick. This would allow you to use it without the extra step of the RC controller that is presently required to tame the thing to reasonable powerchair behavior.

[Burgerman]

I have driven a powerchair that used a couple of brushed boat controllers (175 amp each) with no control software at all. Just did what you told it to do...

The input was from a rc transmitter and reciever as it was so easy to set up.

Now... It was with all softwre in the transmitter "off" so just direct on the sticks, a little "ahem" jumpy! Not uncontrollable but EXTREMELY lively...

With only EXPONENTIAL added to the Aileron, and Elevator channels its totally controllable, once the steering turn speed was reduced. (Servo Travel adjust on the Aileron channel.) And the reverse travel adjusted to about 35 percent.

After that it was just ABSOLUTELY precise and accurate with endless power when you wanted it.

So the only software that the controllers really need are travel ajust back/forward and left right. And exponential.

All that acceleration rubbish just makes them unpredictable. All the other settings really are not required!

Expo gives a smooth response around neutral, but is totally instant when you actually want it to turn or go. And it stops when you tell it too as well. What were the powerchair manufacturers thinking?

I though the roboteq could already be controlled by analog input? Maybe not.

[JoeC]

The Roboteq can do analog in, but my understanding is that it doesn't do it well. The exponential curves available were only "strong" and "weak", then linear or log, and then with the acceleration ramp rate all the way up it was far too lively for the intended users to control. The percentage ramp rates available for RS232 and RC were settable in small increments, and the ramp rates available for the analog input were not the same- only available as a few course chunks. I believe that this also was the case for the top speed. This resulted in a chair that was either slow and sluggish, or too jumpy to be controlled by the person using it. Perhaps a stronger exponential curve and a different joystick could have addressed the problem, but the guy working on it found an easier way out by using an RC controller.

[Burgerman]

The radio control transmitters (at least the good ones) let you choose your own multi point curves, and control throws. Thats the kind of programming powerchairs need. The reason they dont is because you would still get instant full power if you knocked the stick in a resturant... Its great if you accept responsibility, and guard the joystick ALL the time. I do. It wouldnt bother me. But others dont. You only have to be lax once. Think what would happen in a busy bar if you snagged some girls handbag strap or something! Thats why they like soggy delayed controls... If the joystick was snagged, you cought it with a camera strap (or a bra strap - I go to strange places!) or inadvertantly operated it somehow then the resturant/bar would be wrecked! Delays (acceleration) means everything builds slowly so no sudden death and destruction! But no control either...

[JoeC]

Some people are also talking about installing a big red kill switch within reach, just in case something goes wrong. If luck is on your side and you can hit it in time, it would de-energize a contactor to the main battery link, similar to the master key switch in an electric motorcycle or combat robot.

[Burgerman]

That works in the event of a wiring failure or component failure but it still means a 4 year old can run over himself very fast if he graps the stick while you are distracted. But theres no perfect solution. You can understand why therey send chairs out all delayed and soggy though!

[JoeC]

One of the things that I like best about the wheelchair drive electronics over the Roboteq and similar is the ability to switch to a different drive mode based on where you are. There is NO way that I could drive my wife's soccer chair to work on soccer mode. I guess I could, but I am sure that it would be very stressful and wear me out by the time I got where I was going. High turn speed and turn acceleration while going over a bump with no suspension? Not good!

Speaking of suspension, I have to put together a new thread on that topic soon. I recently replaced the suspension in her chair with real shocks, and it's quite a bit different. (Yes, yes, I know, big pneumatic tires!)