Floatwheel: 80A Field Weakening

FAQs & How-tos
1

Tony has been making claims about reaching high speeds by using 80A field weakening. There are several reasons why this is not safe yet.

#1 it hasn’t been tested in the field yet
nosedive prone balance vehicles aren’t the best devices for testing this out.
The most that has been tested fairly thoroughly so far is 50A - and it seems to be stable.
We should ask the guy with his giant Dyno setup to test some corner cases for us - if Tony promises to send him a replacement wheel if something breaks

#2 some early tests at 70-80A have shown nasty side effects
I’ve seen a recent video where a board couldn’t disengage after a freespin with 70A or 80A FW

Further evidence at 60A, from Snoo’s comment below:
“Originally, the field weakening was set to 55A. When I bumped it up to 60A and beyond, weird things started happening at high speeds. The duty cycle fluctuations got notably greater, which risks causing a motor shutdown. Mind you, I ride my Floatwheel at an 85-95% duty cycle.
I did initially change the % at which field weakening kicks in. However, narrowing down that range made the fluctuations even more unpredictable, almost like playing Russian roulette with cutoffs. In short, keep it at around 60%.”

UBox Alert: one UBox80V recently died during freespin at 45A FW (fully charged 18s pack)!

#3 the phase wires aren’t designed for more than 30-50A continuous currents
The Floatwheel phase wires are actually much thinner than on the SuperFlux (CannonCore phase wires look like 14AWG, SuperFlux uses 12AWG) - motor cable is 7.0mm vs 9.4mm on the SuperFlux

#4 VESC firmware v6.2 doesn’t adhere to battery current limits when field weakening is in play!
v6.5 beta has better support for this but it just got added last week, so wait till it has been tested some more

Here a screenshot for evidence how 50A field weakening caused battery current to exceed 90A:

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This is from this video (URL with timestamp): https://youtu.be/IvmQil68H-g?t=529
Battery current = Phase current * Duty Cycle - so 100A * 90% = 90A even though max battery amps were set to 70A

Remember: the BMS is designed to cut power at 80A (after 1 full second of continuous 80A current)

#5 Heat buildup with very high phase currents
Even if 80A were proven to be safe in the VESC firmware, thermals would be a problem.
The controller assembly, the phase wires, and the motor connector aren’t really designed to handle this level of continuous currents - so they would heat up very very quickly. Keep that in mind as well if you’re insisting on pushing the limits

6 Likes
2

Wondering if this could explain my sudden nosedive on a ADV (regular) lately, at just 25 kmh on a flat road. I am not interested in speed at all. All I want is torque for trails, and saftety. I had this set at 50, but can I also set it even lower, like 40 or 30, and be even safer?

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extremely unlikely this is related. Log your rides to understand what’s happening. Could be many things - but not field weakening.

1 Like
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Field Weakening & Current Limits on the Floatwheel - Unleashing the BEAST MODE

Introduction

Hey everyone, I am Snoo from the Burnerz Crew. As an electrical engineer and a passionate Floatwheel rider, I’ve been doing some testing with the VESC settings on my Floatwheel. I made a few discoveries that really transformed my ride, and I thought I’d share it with the community.

Field Weakening Settings

Originally, the field weakening was set to 55A. When I bumped it up to 60A and beyond, weird things started happening at high speeds. The duty cycle fluctuations got notably greater, which risks causing a motor shutdown. Mind you, I ride my Floatwheel at an 85-95% duty cycle.

Field Weakening Percentage

Good question brought up by Paul Ray #1649: I did initially change the % at which field weakening kicks in. However, narrowing down that range made the fluctuations even more unpredictable, almost like playing Russian roulette with cutoffs. In short, keep it at around 60%.

Discharge Current

I pushed the Motor Cfg.-General-Current discharge current from 70A to 90A. For those questioning the BMS limit, my understanding is that it’s a “soft limit” with a duration. Surfdado pointed out that it’s one second, but the principle is right: you won’t get shut down at 87A peak, for instance. But if you push it more while this is measured be ready to save a nose-dive.

Battery Drain and Speed

Yes, your battery will drain faster at 55A field weakening. However, my average speed went up by 4-5 km/h on a Burris 7-inch tire. But my range dropped significantly just riding on these higher speeds.

[Comment from Dado: the range dropped primarily due to the higher speeds, if you increase field weakening (within reason) but keep riding at the same speeds your range shouldn’t change]

Controversy and Discussion

Now, I know there’s some debate about the real impact of changing these settings. While I encourage A-B testing, my personal experience tells me that these tweaks significantly affect the board’s performance. Surfdado mentioned that the VESC firmware will bypass the OG set 50A limit when field weakening is in effect, so keep that in mind.

Conclusion

In all, if you want to push your Floatwheel’s performance, these are settings worth exploring. Hannes will include my “Burnerz - BEAST MODE (Floatwheel)” tune in the float package library for easier access via the VESC Tool app. Test it out and let’s keep this discussion going!

Cheers! :beers:

Snoo

3 Likes
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So I feel like 60a is probably the middle ground. Any reason why floatwheel is recommend to use 1000ms and hypercore motor is 500ms? Or did I get this wrong somewhere?

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60A is not middle ground - where did you read that??? But hey, we always need brave souls to test out settings that would be considered unsafe…

500ms vs 1000ms? This is purely based on lack of knowledge and early testing confusion - imho all of those high times are working against us, I prefer to keep mine at the default 200ms

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I’ve experienced (and heard from others that have experienced) noticeable and uncomfortable changes in board feel for hard acceleration at low speed when using too quick of ramp time, since duty cycle can spike from the increased load even at lower speeds. Grain of salt, I haven’t tested this myself in a long while, but I have heard similar results from others including recently, in which increasing the ramp time to 500ms resolved the issue.

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I don’t read that it was safe I was more generally curious, saw a post where ppl set 80a fw on the floatwheel setup says to put 50a fw so I was curious about 60a. That being said Im running 55a fw currently