What is surge?
Surge behavior is the board telling you that you’re very close to the limit and about to nosedive if you keep pushing.
All FM boards have it, mainly noticeable in 2 situations
- easily noticed by many FM riders: steep uphills when the board is overwhelmed, you can hear a creaking noise and the board sort of jerks up shortly (FM appears to reserve some motor-amps margin just so they can perform the surge behavior)
- less noticeable but heavily relied on by experienced fast riders / racers: at top speed usually in the mid-twenties, but heavily dependent on your battery level, so it appears to be purely duty cycle triggered. The board also briefly surges and riders use this to maintain max speed without nosediving (some people call it “riding the surge”)
For more details see also this: XR-like SURGE Discussion/Feature Request
On FM boards it is an intentional feature, not a bug - apparently it has been added in the early days of the XR.
Who is this for?
Experienced/expert riders/racers who want to be able to ride their board near the limit, if we focus on scenario #2 only (high speed surge)
How does it work ?
It’s currently implemented as a 3-stage setpoint adjustment at 88/90/92% duty, adding 0.5 degrees of setpoint lift each. It is instant so it results in a noticeable but subtle nose wiggle.
When you go back below the threshold then it eases back down within about 20ms.
Can I combine it with duty tiltback?
Yes you can, but it’s best to trigger duty tiltback below 80%. Also if you intend to ride above duty tiltback speeds you probably want the duty tiltback angle fairly mellow (3deg or less)
Has anyone actually tried it yet?
My son and I have tested it using 6s LiPo batteries on an old Funwheel with Fangs… It works great, it is easily noticeable yet subtle enough to not throw you off… When hitting high duty cycles on uphills it is much harder to notice though, but after a few runs I’ve been able to ride right on top of that 90% level without nosedrags
Chase K. has also tested it on his VESC XR with a 15s pack - confirming that he can notice it and that he likes it the way it is.
Cole B. has also been riding it, see his comment below.
Also, testimony from Maclak 15s pack with SuperFlux (March 4th):
And finally from Nico (March 19th):
How can I try it myself?
Here’s the surge-package: it’s 100% compatible with the v0.9 Float Package, it also reports as a v0.9 package. The surge behavior is currently not configurable. It is automatically enabled as long as your duty cycle tiltback is configured to start below 82% duty cycle.
float_surge.vescpkg on Google Drive
For testing I had duty cycle angle at 0 degrees - but Chase had his duty tiltback at 80% and 3 degrees.
What should I expect to feel?
The new Float Package surge behavior is purely focused on duty cycle based situations, not torque based situations.
The easiest way to feel “surge” in the Float Package is when you inch your way toward 90% duty cycle on smooth road. If you do it on slightly uphill you’ll experience surge at slightly lower speeds than if you try it on a completely level road.
On steeper uphills you will also get this duty cycle based surge, but it is less noticeable due to the already high amps needed to maintain speed or accelerate up the hill. So it may take some practice to develop a feel for it.
If you have a buzzer installed, this test-version of the package does trigger the buzzer whenever surge is triggered to give you additional confirmation that surge is happening
Limitations:
If you lead-foot your way toward the speed limit your likely going to blow right past the surge behavior and there’ll only be a short blip that you might not even feel because you’re already nosediving. Finesse is required!
The surge behavior is not amp based, if you’re near or at the amp limit there’s simply no good way for the board to alert you anyway. Lowering your amp limit just to be able to perform surge like FM does makes no sense imho.
Safety checklist
- Enable field weakening - at least 30A
- Set duty tiltback to start at 80% or lower
- Configure a low duty tiltback angle (3 degrees or less, 0 is fine too if you want to only rely on surge)
- If you have FloatControl configure a duty alarm for ~90%
- Disable duty tiltback alerts in FloatControl
- Pad up!
it really does make the ride feel like you’re in the edge of a nose dive, but hey that’s it’s purpose. Personally it just gives me anxiety 