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Why is my VESC Speed (in MPH) half what it should be?

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ALarabie
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Why is my VESC Speed (in MPH) half what it should be?

Hi all.

I've just installed an FSESC 4.20 Dual 100A in a WowGo AT2 and everything is running really nice so far.

The only thing I can't figure out is why my MPH speed display is halved... 

Im using a Maytech MTSKR2005WF controller over UART. On this controller you can have it display the data its getting over UART, like Speed, Voltage, Mosfet Temps, Distance traveled, etc...

I rode side by side with my buddy on his Evolve GTR to compared speeds, and mine was displaying half of his. And at full speed it only shows 10 to 11 mph. Pretty much half of the board's rated top speed.

I double checked my gear/wheel diameter and they are all correct; 15t/66t and 190mm wheel diameter. 4.4 Gear ratio.

Is it because its a Dual ESC and the speed calculation are only done for 1 of the ESCs? (sounds dumb when I type it out cheeky). 

Anyway, I cant find anything in VESC Tool that relates to MPH or Speed calculation of any kind.

I have somany more questions about VESC Tool, but we'll start here for now..

AL

vadicus
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Motor poles affect speed calculation as well. Try values of 4 or 2 or the actual poles you motor has.

 

 

NextGen FOC High voltage 144v/34s, 30kw (https://vesc-project.com/node/1477)

ALarabie
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Thanks for the reply Vadicus. 

I have it set to 14 (which was the default) and altho I can't find the exact specs for these Wowgo motors (6368 170kv 1500w), similar motors are 14 pole as well. And I can't see the magnets to count them.

Since 14 poles is 7 pole pairs. Should I try 7? Would cutting the pole count in 1/2 double the speed calc?

Also, any bad side effects of having the poles set wrong?

Any other suggestions?

vadicus
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Yes, decreasing the pole count will increase speed calculations.

Other than incorrect speed (distance, consumption, etc) calculations, there is no side effects. The controller doesn't care much what you put in there.

Double check your gear ratio and the wheel diameter. I see this skateboard comes with 175 or 120mm diameter wheels. You set 190mm which seems a bit too high.

Once you think you have everything dialed in, use a phone gps speedometer to fgo exactly one mile and compare the phone readings and your controller calculations. Provided you have the wheel diameter and gear ratio set correctly, that will give you a good idea if the pole count is right. like if you get 1/2 of the distance, you know your pole count is off by 1/2.

 

 

NextGen FOC High voltage 144v/34s, 30kw (https://vesc-project.com/node/1477)

ALarabie
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Ok, Ill try that. I didn't mention, I'm not riding the stock wheels currently. I'm riding 8" off road tires (200x50mm). I put calipers on em and they came out at 190mm (189.7mm now that they're worn a bit). The VESC setup guides I've looked at all say its important to be precise here.  I've triple checked everything else.

As for Speed and Distance, I've been tracking my rides, and I've also been saving Real Time Data from the ESC (to my phone over Bluetooth) for Analysis. 

Looking at that, the VESC tracked the distance of that ride as 14.63 miles (23539.91 meters). Looking at the 2 other tracking apps I also had running (Evolve and Ride), those both tracked the same distance of 12.6 miles.

VESC RT data reported Avg. Speed of 4.91 mph, with the other 2 tracking apps showing 11.8 mph and 11.6 mph respectively. The RT Data does not show top speed, only Avg.

I'll change the poles before my next ride and see what I get.

Thanks again.

ALarabie
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Ok, just got back from a ride. Got mixed results.

Changing the motor poles in iOS VESC tool did nothing, the displayed speed was always off by about 1/2. I could only set even numbers, so I tried going down to 4 and up to 28. Neither seem to change anything.

But I remember the Maytech controller also has a motor pole setting also.  So, I set the pole in VESC back to 14 and changed the motor pole setting to 7 in the Maytech controller, now the speed is bang on.

The Travel Distance tho.. Wow that is messed up..  I was watching the distance go up by 1 mile about every 30 feet or so.. The odometer is only two digits, so the mileage would keep going over 99 and starting over from 0 again. I started tracking RT Data, but after changing some settings I rebooted the ESC and forgot to start tracking RT data again, so I have no data to look at... boo

As its stands now, the MPH now display correctly in the handset. Yay!

But the Traveled distance is just plain wacky. 

vadicus
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it's possible that the remote has it's own settings for speed calculation. I wonder if the manufacturer provides a manual or some kind of support. 

 

 

NextGen FOC High voltage 144v/34s, 30kw (https://vesc-project.com/node/1477)