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If a DC Wheelchair motor is rated at 9.4 Amps...

If a DC Wheelchair motor is rated at 9.4 Amps, is that the under full load?

I can't find much in the way of specs, but the motors are clearly labelled..

Type: SSG0220
Voltage(V): 24v DC
Amperage(A): 9.4A

  ** EDIT **

I didn't get the answer I was seeking, so today I pulled the base out. After some testing, the results indicate that the 9.4v must be an average load reading.

With the base lifted (wheel turning freely) the current draw was 3.3A

With the base settled (wheels in contact with a sheet of plywood), the base pushed up against the wall and some weight applied... The max current draw was 15.2A

I posted the results for anyone who may search for it in the future.

Rick

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Sisco's picture

I already ordered a Sabertooth 2x25 so even if these motors only require 9.4A I have room to grow (or use this controller with other motors). The 2x25 will be at my door tomorrow.

My main interest is if the rated Amps, in this case 9.4A, printed on a motor is typically figured with the motor under full load.

I will pull the base out today and test the motors to get my answer. The motors are still mounted to the base of the chair, so I can test current draw at idle, on level floor and up against something. I just didn't know if someone here already had the answer.

Rick

Bajdi's picture

When you make a H-bridge with relays you will not be able to control the speed of the motor. You can find some reasonably priced H-bridges on Ebay, made in China: http://tinyurl.com/cjthn45

fifer253's picture

Indeed you cannot, unless you put a MOSFET in series with the power supply, and for $11 for enough relays for two motor controls plus an extra, you can spend a fair bit of cash on two high power MOSFETS and still come out spending less than two of the boards you mentioned. Plus you have 60-80 amps and LOTS of voltage handling to work with to make it really overkill :)

Chris the Carpenter's picture

You know what dude, just go ahead and get the 25A driver, and here's why.

You got big ass motors there and you are going to be moving a big, heavy robot. Let's say the 9.4A is no-load, well right off the bat, you are over the 10A driver as soon as it has to move something. Let's say the 9.4A is mid-range --Well, mid-range and just drivin' around is average for your motor, but is 100% of your driver. Let's say it is peak and you will only draw 6 or 7 amps normally. Well, at start-up and direction changes, your amps are going to peak -not to mention at 7 amps, you are still at 70% of your driver (continuously).

I would go 25A if you can afford it. Things are much happeier (and last much longer) when they are only asked to work at 40 or 50%. -And the few times your motors suck a good burst of power, you have overhead to handle it.

Yeah, dude. Screw the "break your wrist" amp test, just get the bigger driver.

fifer253's picture
Sisco's picture

I will bring it in tomorrow and try that. I just didn't know if anyone knew off the top of their head. Perhaps someone who has already worked with wheelchair motors.

Chris the Carpenter's picture

Really easy way to find out...

Hold the shaft firm with some vise grips and don't let it spin. Apply full power and read the current draw with a meter. Done!

Maxhirez's picture
"A SKOWHEGAN MAN BROKE BOTH WRISTS TODAY WHEN..."
Maxhirez's picture
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mixmar's picture

I read a post from you somewhere where you adviced to just measure the resistanse throught the coil and take the lowest value and apply ohm law to it. that worked like a charm for me. good advice. That might be an option here unless taking CTC(nice bearded man)'s advice on going with the 25Amp one.