ElectricMotorcycleForum.com
Tech => Home Brew => Topic started by: Gregski on September 10, 2011, 09:14:23 AM
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So I decided to strap my trusty HP Netbook to my gas tank and tether it to my Alltrax AXE4834 programmable controller via a serial/USB cable and by running their ControllerPro software get some excellent data
what I like best about this setup is that it shows you not only the voltage but the amps without an external shunt as it gets the data directly from the controller, among other things like throttle position, a date/time stamp, and temperature (of something called a diode, lol)
what boggles the mind is that Alltrax has just finally offered the voltage reading on their homegrown Ex-Ray gauge/speedometer, for a while their original device did not even show us that, how lame is that, maybe in a year or two they will display the amps, lol, meanwhile I am thinking of buying an old Windows Mobile phone off of eBay and running ControllerPro on it and using it as my gauge, what do you guys make of that hack/idea?
QUESTIONS:
1. What's the difference between Output Current and Battery Current? And how can I draw 192 amps from the battery pack but "output" 375 at 6:41:08 pm?
2. How can I draw 260 amps from the battery pack when I am using a 200 amp fuse, wouldn't it blow?
3. I forget.... lol
please note I had to trim the attached data file do to this forums file size limitations
(http://gregandsandy.com//wattana/pics/small/DSCN9790.jpg)
(http://gregandsandy.com//wattana/pics/small/DSCN9791.jpg)
(http://gregandsandy.com//wattana/pics/small/DSCN9792.jpg)
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The current difference will be due to the PWM, if you are at 50% PWM your output voltage is 50% of the input, because power in = power out, the current in, is half the current out. That is a simplification of things, but I think that will be the main cause of discrepancy between the readings.
Not too sure about the fuse, possibly the rated current is less than the current it takes to blow it, or it is really slow-blow, or a combination of both.
A phone hack could be interesting, are the proper gauges that expensive that it is worth doing though?
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A phone hack could be interesting, are the proper gauges that expensive that it is worth doing though?
I am a computer geek by trade, so I think I may be able to pull it off, plus I noticed the Alltrax program is a self contained executable and not a piece of software you have to install in the traditional sense where there is a setup.exe file that installs a bunch of .dll libraries and modifies your computer registry.... zzz zzz zzz wake up people, lol
It is very difficult to find a basic gauge that plugs directly into the smart controller like I have via a serial port and does what we need, technically only one does it the Ex-Ray. However the Ex-Ray from Alltrax did not even show you the voltage, just your speed, and average speed, till recently, but it still doesn't show you the amps or the Watt Hours, etc
The Cycle Analyst shows you the volts, the amps, and the amp hours left however it requires an external shunt and a mickey mouse magnetic speedometer pickup off your wheel
there is a third one but shoot I forget what it is called, and those are about it that I know of, all north of $200 bucks
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A friend of mine tried running the Alltrax ControlPro software on his old Windows Mobile device and it does not work, oh well
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The current difference will be due to the PWM, if you are at 50% PWM your output voltage is 50% of the input, because power in = power out, the current in, is half the current out.
OK, if I had a 72 volt controller would it also work the other way around, where the controller can increase the 48 voltage by 50% to say 72 volts while dropping the current by 50% ie 200 amps to 100 amps?
Shoot I just confused myself the power output has to equal and in my example its 9600 vs 7200 - wtf ?
I would have to increase the voltage by 50% while cutting the amps by 33%, this is so confusing....
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No, it doesn't.
Controllers are buck converters. The PWM only works at Pack voltage down to 0. You can go 0-100% PWM, there's no such thing as 150% PWM.
So yeah, increase voltage and you decrease current.
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No, it doesn't.
Controllers are buck converters. The PWM only works at Pack voltage down to 0. You can go 0-100% PWM, there's no such thing as 150% PWM.
So yeah, increase voltage and you decrease current.
thank you very muxh frodus I think I get it, so 50% would look like this
(http://savannahindigo.files.wordpress.com/2011/03/square_wave.jpg)
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logged another ride today, actually did the first half or so of my one way ride to work, so I logged roughly 5 miles, this included two freeway overpasses, anyway my top speed was roughly 35 MPH except when climbing it dropped to 20 MPH
let me just say how much I appreciate you guys taking the time to read this and help out, also I hope you find my posts funny and sarcastic rather than moronic, lol
so here's what I noticed today, and this just blows my mind, at one time the data read
Output Current: 470
Battery Current: 141.9
Battery Voltage 45.2
Now I am not sure what battery voltage means (as I excel at over thinking things, and easily confuse that number with AH), I guess it means how much it's drawing at that time so 45.2 volts X 141.9 amps = 6413.88 Watts
So does that mean at 470 amps I was running on 13.65 volts?
If so, that means I am getting this.
If so, that means that they might as well not put any amp ratings on controllers as my 300 amp Alltrax just gave new meaning to giving it 150% - LOL or does this mean my bad boy can pull up to 300 amps at 48 volts or 14,400 watts of pure DC power while spewing out what ever combination of amp/volts it can muster up to 14,400 watts?
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Sounds right to me! But yeh, that is a big output current, not sure what is going on there.
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Are you getting that from the Alltrax Software? or just via hyperTerminal?
Having more amps on the output than the input is normal for a buck converter. Pack voltage x Pack Amps = a wattage = (efficiency loss) x Motor amps x (Pack voltage x PWM%).
So yeah, basically you're running about 13V on the motor. Volts is directly proportional to RPM, so you're at ~27% speed.
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Are you getting that from the Alltrax Software? or just via hyperTerminal?
From the Alltrax ControlPro software.
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400+ seems high, but those are peak values, not sustained. I think it's a 300A all day controller. You may see some small spikes that go that high. How long do the 400A peaks sustain?
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400+ seems high, but those are peak values, not sustained. I think it's a 300A all day controller. You may see some small spikes that go that high. How long do the 400A peaks sustain?
You are once again correct. I went back and looked at the data and I saw 2 second spans where the Output Current was above 300 amps, however it was only above 400 amps for a split second if that
I have to say I love this stuff, I enjoy analyzing the data, and would highly recommend newbies get programmable controllers or some sort of controllers that allow them to connect a laptop to and or display of some sorts and see what the machine is doing, have I not done this with my laptop I would wrongly assume my controller is spewing only up to 300 amps, which is not the case
I am still sorta not ok with something being rated at 300 amps and putting out 420, it's like saying hey this cars top speed is 135 MPH but you know sometimes it goes 160 MPH, lol
thanks again for your help and explanations much appreciated, much !
Date - Time - Throttle Position - Diode Temp - Battery Voltage - Output Current - Battery Current
9/14/2011 18:47:59.699 20 34.9 49.3 380 77.5
9/14/2011 18:47:59.793 30 35.4 45.2 470 141.9
9/14/2011 18:47:59.871 33 34.9 44.6 445 148.3
9/14/2011 18:47:59.964 37 34.9 44.6 440 163.9
9/14/2011 18:48:00.042 42 34.9 44.6 420 174.6
9/14/2011 18:48:00.136 46 34.9 44.8 390 180.5
9/14/2011 18:48:00.214 51 34.9 44.5 370 187.2
9/14/2011 18:48:00.307 59 34.9 44.8 360 213.2
9/14/2011 18:48:00.401 76 34.9 44.6 365 277.7
9/14/2011 18:48:00.479 76 34.9 45.0 370 281.5
9/14/2011 18:48:00.573 76 35.4 44.6 345 263.8
9/14/2011 18:48:00.651 77 34.9 44.9 345 265.2
9/14/2011 18:48:00.744 77 34.9 45.1 365 282.0
9/14/2011 18:48:00.822 77 34.9 44.8 345 266.5
9/14/2011 18:48:00.916 78 34.9 44.4 325 252.4
9/14/2011 18:48:00.994 78 34.9 44.4 305 236.8
9/14/2011 18:48:01.087 82 34.9 44.6 315 256.9
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It's kinda of like a single cylinder bike, if you were to look only at the torque generated on the expansion stroke, you would have four times the usable torque. To rate the engine at something it can only achieve a small percentage of the time would be silly though, just like the Alltrax.
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It's fine gregski,
you just need to wrap your mind around Instantanious and continuous. They'll do 300A Average, but the controller inside might have small spikes that put out a little more current than it wants, it backs off and keeps that current under 300A. The processor inside is constantly regulating the output current to the setting inside the controller while you give the throttle signal and speed up/slow down. It's all working fine, I wouldn't worry about it, Alltrax's are beasts.
Also, they're underrated so when they say 300A, they mean it.
Not like kelly when 600A means 500A for 1 minute and 240A continuous......
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So I spent the last umpteen months waiting on an affordable Alltrax AXE7245 450a 24-72v controller to show up on eBay and it finally did, for $275 (including shipping) = score!
So my new (used) controller arrived yesterday.
I found out you use the same 3A diode for 200A and up contactors so we are good there, however I am using a 470 ohm 10W resistor now and I need the 1000 Ohm 10W for the 72 volt system. Does that mean I don’t need to change until I add two more batteries? Right now I just want to try the new controller with my existing four 12 volt lead acid batteries, ie 48 volt system.
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Monday was Martin Luther King Jr. holiday so I tinkered with the bike, and swapped out the 300 amp controller with the new(er) 450 am controller, and I am pleasantly pleased. First of all the 450 is about 2 inches longer so I had to mount it vertically instead of horizontally, but that's neither here nor there. The important thing is that even with only 4 lead acid batteries (48 volts) the bike is much quicker and I can get up to just shy of 40 mph. I weigh 200lbs so that is pretty darn good. I can't wait to add the other two batteries for my ultimate 72 volt goal / system... stay tuned.