Otto Bock 600 Review

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Otto Bock 600 Review

Postby Burgerman » 28 Feb 2010, 13:46

http://www.wheelchairdriver.com/otto-bock-600-.htm (Goes to my review page)

Add your own comments or pictures and experiences on the Otto Bock 600 Powerchair if you have experience of this chair here and I will link to this thread from that page.

Add comments even if you dont have direct experience too if you want, but please say so!

My summary - a little bose heavy, bad programming (like all chairs).

Thanks. Burgerman
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Re: Otto Bock 600 Review

Postby JoeC » 08 Mar 2010, 18:15

Any further information on this chair? At the US Western regional power soccer tournament this weekend, I observed a new version of this chair in pre-release form. It was factory fitted with mounting points for the foot guard, and had a factory installed cooling fan on the motor controller. Although the chair appeared to have some power, it was lousy for the sport. The seat position was way too far forward, preventing rapid turns or good traction. It was easy to make the chair do a "donut", spinning in a relatively small circle with one tire squealing on a gymnasium floor. It looked and sounded kind of impressive, if you don't know anything about traction or weight distribution.

The motors were marked 12V, 350 watts, but I did not see any other details that stuck in my mind. Since the motors are actually taking 24 volts, the nameplate would indicate that they would be nominally 1400 watt motors.

Nothing on this chair looked especially interesting, other than that a second manufacturer is making a purpose-built sports chair. What I'd like to hear is if anybody knows about the "enAble50" electronics system, apparently built in-house by Otto Bock.
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Re: Otto Bock 600 Review

Postby Burgerman » 08 Mar 2010, 19:09

The motors were marked 12V, 350 watts, but I did not see any other details that stuck in my mind. Since the motors are actually taking 24 volts, the nameplate would indicate that they would be nominally 1400 watt motors.

The above confused me a little!!?

I have no idea about this chair, never heard of it. 1400 watts? 350 watts at 12v? Thats doesent make any sense? :) Did you type something wrong?

Unless you mean 12v 350 watt x2 because of of double voltage, and x2 again because of two motors?

Never understood the watts thing on motors because my 900(?) watt motors (each?) take 100 amps (controller limit) easily and thats way more than the rated amps according to Mr Ohm and the law. 100 x 24 = 2400 watts? Unless its a continuous rating which is pretty meaningless.
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Re: Otto Bock 600 Review

Postby JoeC » 08 Mar 2010, 19:31

No, I meant 1400 watts at 24 volts- here's a chart with all the different ways to arrange Ohm's law:

http://www.sengpielaudio.com/calculator-ohm.htm

Voltage squared over R is power, so doubling the voltage quadruples the power. The question is about whether or not a motor can take it! The "power rating" of a motor is what's ambiguous, because you could do it different ways. Is it peak mechanical power output? Is it the highest electrical input that the motor can sustain for hours without melting down? Is it the maximum power that it can take for a few seconds without burning? Maybe it's the stall current times the operating voltage- I think that one is closer to the standard.

I don't really know what to make of wattage ratings on a motor unless all of the specs (voltage, time, allowed temperature, etc) are spelled out, not as an apples-to-apples comparison.

Looking at the voltage relationship to motor power once again makes me even more determined to do this wiring upgrade. I haven't done the measurements yet (tournament all weekend), but thicker wires can only improve things. I'll be upgrading the battery cable at the very least in order to use the new charger.
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Re: Otto Bock 600 Review

Postby Burgerman » 08 Mar 2010, 21:44

Interesting calculator page now in favorites!

I did my own simple ohms law one years ago here:

But I forgot how to do close so you have to pres ESC instead...

It may need to be told to run in XP compatibility (right click it)...

Attached for amusement value!

You will definitely see a difference with the cables.
I am using 8mm (stock 6 square mm) and if I charge at 40 amps they get hot...
Yours are thinner than both! Theres probably not much difference between the motors and the wirings impedance...

Definitely measre the full power voltage at the motor and at the battery while stalled. I am interested! You are probably feeding about 14v to the motors!
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Ohms Law Calc.zip
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Re: Otto Bock 600 Review

Postby JoeC » 08 Mar 2010, 22:51

I'm slated to do more chair work tonight, along with house work, so I'll try to get the measurements done while I'm at it. I forget if this was your idea or mine, but I'm going to drill out a spare brush cap to measure the voltage at the actual brush.

I expect that at stall I will see less than 10 volts across the motor- but that's just due to the resistance and current limit. I expect to see about 0.3 volts per motor lead, and less than .7 volts from the battery cables. The remainder will be across the controller, but this is where I get kind of fuzzy on PWM and ohm's law. Joule heating should only occur during the "on" part of the PWM cycle, so there should be a lot less energy wasted than the voltage and current measured into and out of the controller would suggest.

What will be a little more interesting will be to do the measurement during a dead-start acceleration at the point in time around 3 or 4 mph where the motors would like to draw no more than 80 amps each from a 24 volt supply. That would show the maximum current through the controller at the maximum voltage applied to the motors- the peak electrical power. This is where I think that controller efficiency will show its true benefit.

The batteries and cables only care about current, not actual power out of the controller, so a stall test will still be informative regarding voltage losses.
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Re: Otto Bock 600 Review

Postby JoeC » 09 Mar 2010, 08:31

Just tried to do that measurement, but my Tenma clamp meter seems to be acting up. The 0-40 amp range seems fine, but when I click over to get up to the 0-400 range, it says I'm only measuring up to around 53 amps drawn from the battery. Did some metal sawing and fitting before I got around to the electrical stuff tonight, so I will have to dig out my Fluke probe another time.
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