How should the VESC "feel" on a board?

General topics and discussions about the VESC and its development.
rogerd
Posts: 17
Joined: 21 Dec 2015, 15:46

How should the VESC "feel" on a board?

Postby rogerd » 23 Dec 2015, 16:37

I've just had my 1st test of my VESC on my 10s brushless longboard (was 6S on a 150A EZrun car esc). Just up and down the drive (a long drive) and didnt go anywhere near top speed.

1) Smooth start - LOVE IT!
2) Smooth acceleration - really like it.
3) Smooth braking - LOVE IT.

Now the one quesiton I have, is that the acceleration , compared to my car esc setup, is far more gentle with the VESC. To the point that I can hold the throttle wide open after start up and the speed will gradually build up. On my board with 6S and the car esc, doing that would throw you off the board!

Is this how it's meant to be? I like the smooth acceleration, but I would like a little more punch to it in case I want to get moving faster.

okp
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Re: How should the VESC "feel" on a board?

Postby okp » 23 Dec 2015, 17:26

you can play with startup boost ... don't put it higher than 0.090 ... and motor amps.

rogerd
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Joined: 21 Dec 2015, 15:46

Re: How should the VESC "feel" on a board?

Postby rogerd » 23 Dec 2015, 18:08

I have my startup boost at 0.1 - it's what I need to get it to start smoothly. I read that it was ok to go up to 0.15 somwhere?

By motor Amps - do you mean Motor Max current?

benjamin
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Re: How should the VESC "feel" on a board?

Postby benjamin » 23 Dec 2015, 19:06

Which motor do you have? As okp mentioned, you can increase the motor current. Depending on the motor, you can try 80A or so. The field where you change the motor current is motor max. You can also increase batt max to the same value if your battery can supply that much current (LiPo batteries usually can, but not e.g. the space cell from enertion).

rogerd
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Joined: 21 Dec 2015, 15:46

Re: How should the VESC "feel" on a board?

Postby rogerd » 23 Dec 2015, 23:29

It's a Turnigy SK3 6374 245 rated at 70 amps. My batt max is set at a conservative 150Amps as I have 2x 4Ah 25c packs in parallel (200amps theoretically).

I'm just a little suprised I've gone from quite agressive accel on 6s to very gently accel on 10s. I appreciate it's a different type of speed control, and is much more subtle. I just want to check I'm running as I should be.

I've got low voltage protection on at start 37v, cut 35 volt . If it's dry enough I'll test tomorrow and see what amps I'm pulling under full load.

benjamin
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Re: How should the VESC "feel" on a board?

Postby benjamin » 24 Dec 2015, 02:04

You should not set the battery current limit higher than the motor current limit, but it does not matter that much. The battery current is always lower than or equal to the motor current.

For that motor you can try with up to 80 or 90A current limit, but I wouldn't go higher than that.

rogerd
Posts: 17
Joined: 21 Dec 2015, 15:46

Re: How should the VESC "feel" on a board?

Postby rogerd » 24 Dec 2015, 10:25

Curious. I've checked the settings. I've upped the motor to 75A (from 65A), I disable voltage cut off. Backed the max battery amps down to 80A.

It makes no difference at all. I accellerate from standstill, under full throttle, but there is no risk of falling backwards (should there be? or is the PID in the esc set to avoid this?). Loving the smooth start and lack of esc heat.

I put a HK amp/watt meter inline with the battery and it reads a peak of 11Amps going from standstill, wide open throttle - but only in a very short distance 0 i.e. about 5 board lengths (in my hallway). I am assuming it needs more space before it piles on the power?

I test it with real time monitoring in your windows app with the wheel in the air, and on full throttle I manage to get the graph to peak at around 50Amp motor draw, a very brief spike, then it abviously settles way down as there is no real load. I wonder whether the spike is so short it's not long enough for my HK current meter to log it.

rogerd
Posts: 17
Joined: 21 Dec 2015, 15:46

Re: How should the VESC "feel" on a board?

Postby rogerd » 24 Dec 2015, 12:20

Just tested it on a longer run, approaching full speed.

Max draw was 50amps. Accell is still very sedate.

Max motor amps are set at 75amps.

rogerd
Posts: 17
Joined: 21 Dec 2015, 15:46

Re: How should the VESC "feel" on a board?

Postby rogerd » 27 Dec 2015, 16:25

Little update - might be the chip temperature protection kicking in. I get poor performance all round after a short distance. Opening the case the ESC is in makes things faster again. Will test with a laptop connected and upate.

rogerd
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Joined: 21 Dec 2015, 15:46

Re: How should the VESC "feel" on a board?

Postby rogerd » 28 Dec 2015, 18:10

OK - so an update - I've done a few tests (with a laptop plugged in). The temperature is certainly one of the problems. I still feel the VESC is lacking in power. Accelleration/torque power.

OLD config (same motor, etc)
6s 20c 3000mah batts in parallel x4 (12Ah)
Turnighy SK3 6354 245Kv motor
16T pinion pulley, 42T main pulley.
EZRun 150Amp esc.

Measures (today) - 100amps peak (at 6s = 24 volts) on the flat wide open throttle. = 2400 watts. Motor is rated at 2700 watts.

Hard pulling performance (you HAVE to kick off to get going - over aggressive throttle will cog) - you need to lean forward to cope with mid level acceleration. Full acceleration without being ready and you'll come off the board. Fairly loud motor. Strong braking. Hills present no issue at all.


NEW config (same motor - slightly smaller pulley to allow for higher voltage)
10s 25c 4000Mah batts x 2 in parallel (8Ah)
Turnighy SK3 6354 245Kv motor
15T pinion pulley, 42T main pulley.
VESC

Measured (today) 60A peak (at 10s = 40 volts) on the flat wide open throttle. = 2400 watts. Exactly the same as my old setup.

Smooth start from still. Gentle accelleration - you can go wide open all the way to top speed. The board will get fast eventually and then feels fairly responsive. Hills cause the motor to slow right down to a limited top speed. This seems heat related on the ESC. Putting the ESC in a box means it slows down even on the flats.

So I'm using the same wattage on both setups but the VESC setup is really lacking in power which seems to be partly limited by the ESC temperatures. I watched the temps on my laptop whils skating but this is tricky when riding... But I saw them only climb to the mid 70's - was hard to tell (how do I make a log on my laptop I can read after?). But I'm not convinced that's the root cause. It feels like the motor is not being driven properly - particularly as the old setup uses 2400 watts to throw me off the board, and the new setup uses 2400 watts for a very gentle acceleration.

I've attached my current config: are there any obvious errors in it?

https://dl.dropboxusercontent.com/u/139 ... kmotor.xml


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