Onewheel Build Guide [Continuation from "old" forum]

E-Bikes/OneWheel/EUC/GoCart/Scooter
#82

Yeah i could have probably made them better. But the errors or weak points will hardly burn down my house.

Put fish paper between the groups of batteries in parallel.

Good point, but how to glue the batteries then, also the pack will end up much bigger.

Put fish orings on the + ends

Takes alot of time and in my opinion not really necessary. The batteries already have a o-ring on them and i have never seen one rubbed trough

Route balance wires so that they are not on top of each other. Use kapton tape to secure routing. Place a line of fishpaper where the wires will rest

As i said im not worried about balance wire trouble. They are awg 30 and in the worst case they just burn up.

For+ and - main leads, don’t solder them directly to the battery (see video of how he did it with a little tab and fishpaper where it rests on the sides)

I use a 100w soldering iron and the contact time is very short and not directly on the cells. Also a external tab would create another weakpoint on the battery (i like to be able to hold my battery at the power leads if i have to)

Once battery is done, wrap with kapton tape.

Why? kapton tape is good for holding things down and is very heat resistant. i never heard about its abrasion resistive capabilies

Optionally, I’ve seen some people put a layer of foam
Wrap in the heat shrink

Good point, i should do that with all my batteries. Im looking for something like a large glass fiber tube that i can put under the heat shrink.

As far as protecting the ESC you could make a 3d printed case.

I like your 3d print idea. I could make a fitting case for the a200s that includes the heat sink. I still dont like that the heat sink is connected to battery negative (this is why my last controller was destroyed)

Other than that, i installed a fresh a200s controller but im still having trouble with my IMU. I use very short wires but its still not enough stopping the EMI problems. The project is put on hold and i will probably use a different controller with integrated IMU (Cheap FOCer 2). So i will have to modify the motor to delta for 12s.

2 Likes
#83

What are the imu problems? Have you tried the new IMU calibration tool?

#84

Yeah its not the calibration, when there are some hard acceleration or deccelartions, the IMU somehow crashes and if you look at the graph it just rises slowly (same as roll) until you cut the power and reboot.

I had the same problem before and it went better when i moved the imu away from the high power lines/battery.

#85

When you say “just rises” you mean it no longer shows movement? Or trends upward but still shows movement?

Lots of people are using external imu without a problem. Seems like a shame to downgrade from an a200s to a cheap focer.

#86

Still deciding on batteries. Has anyone built one of these using Samsung 40Ts or other 21700 cell? Trying to absorb as much up to date info on cells as I can but atm am tossing up whether to go for a 12S2P 40T pack or 12S3/4P 30Q pack.

Am in Australia so my will probably end up ordering from BatteryQueen or TechAroundYou, as my selection of cost effective suppliers is pretty slim. Can purchase in pretty large quantities and have the use of an ABN, but just want to make sure I’m getting the best all rounder cells for a variety of projects (first and foremost my onewheel tho).

1 Like
#87

Its slowly moving upwards and because of the wrong values the balance app goes into dead state. Quite dangerous too when not in “test mode” and with high amp values because somtimes there is a sudden full acceleration.

#88

Are you powering the IMU from 3.3V or 5V? Powering from 5V seems to give more noise. Also are you using offset compensations values in the VESC Tools IMU tab?

#89

I use the 3.3v line. Did not use any offset compensations.

#90

Some people while building drones have issues with the ESC draw creating too much noise on the 5v line and use a small external power regulator inbetween such as a pololu to fix the issue.

@Astridash I’ve seen a few people with XRs upgrading to 21700/20700b cells: chibatterysystems[dot]com/services/onewheel-xr-xxr

If you have enough space and the batteries are rated with high enough amp output, as long as cost isn’t an issue I don’t see why you wouldn’t want to go with 21700/20700 over 18650 since they have superior energy density.

#91

You are probably referring to a BEC used to clean up the video feed on FPV drones.

For the IMU board on a Onewheel an independent BEC doesn’t make any sense as the VESC already has 3.3V and 5V lines that are clean enough.

#92

Maybe is talking about L-C Filter?

#93

Hey there guys,

Finnaly got my onewheel working. I installed the CheapFocer v2 with an integrated IMU, altough only at 12s its way better than with the a200s and external IMU. Whats really nice is that i am now able to change settings on the fly via bluetooth. That makes tuning the PID and tiltback options really easy.

20200601_124621
20200601_124621768×1024 190 KB

20200602_150617
20200602_150617768×1024 133 KB

Still my onewheel threw me off 3 times today. It just plunges foreward, its not the tiltback it just happens randomly. I recorded a logfile while it happend twice. Maybe you can see something i dont?

Anmerkung 2020-06-02 183416
Anmerkung 2020-06-02 1834161030×293 51.4 KB

onewheel_log_3 - Kopie.csv (1.1 MB)

onewheel_log_no_loc.csv (301.1 KB)

1 Like
#94

Just getting mine up and running. With the USB plugged in, I was noticing I can get it to go to the dead just by moving back and forth aggressively. I don’t see the duty cycle spiking above 94% (what I have it set to) but I think that is the only reason it would get in the dead state. I set it to 99% which it can’t get to and I don’t have that happen anymore…

2 Likes
#95

Thank you brycej,

Yes that could be it, i found that after a crash i had to reset the board by unplugging and then replugging it.

Is duty cycle the only value that brings it to a dead state? Maybe its possible to keep this safty setting by adding some overspeed delay?

I have experimented with some PID settings. Adding integer makes the board want to take off immediatly. Did any of you had luck with this?

This are my current settings:

Motor Type: phub-188
ESC: cheapFOCER v2

Motor Type: FOC

Motor Current Max: 80A
Motor Current Max Brake: -80A
Absolute Maximum Current: 100A

Battery Current Max: 60A
Battery Current Max Regen: -60A

Startup Pitch Axis Angle Tolerance: 12
Startup Roll Axis Angle Tolerance: 20
Startup Centering Speed: 30
Brake Current: 0

Tiltback Angle: 5
Tiltback Speed: 7.0
Duty Cycle Tiltback: 0.80

Cutoff Duty: 0.99 (for testing)
Overspeed Delay: 0

Pitch Axis Cutoff: 22
Roll Axis Cutoff: 30

P: 7
I: 0
D: 120

Loop: 1000Hz

Sample Rate: 1000Hz

Madgwick Beta: 0.020

Gyro Offset corrected by ~0.15

All other values are default. Something unusual?

If you found settings that work for you can you please post them too?

2 Likes
#96

Are you sure it’s not the exposed power wires hitting something? Looks scary :grimacing: Any stored VESC errors after that event?

On a completely different topic, is there a lot of difference between the tires that come with these motors? I see the profile on yours is convex, bulging out at the center. Mine is the opposite, concave with the center depressed like this

IMG-20190719-WA0009
IMG-20190719-WA00091372×1024 152 KB

It’s worn a bit more level with use but it’s still like that. What pressur do you inflate to? I go with 20 psi.

#97

Hey jopj,

Its running fine now, i had to tune some settings. The wire was just exposed for the picture, i was not riding like this. I inflate to arounf 16psi

2 Likes
#98

Tire pressure will have a big difference in the tire profile. Higher pressure, more convex. Could be differences in tires too. Width of the wheel will change the profile too. Hopefully that isn’t the case.

#99

I’d think so too, but that doesn’t seem to happen for me. From the maximum 20 psi suggested on the tire down to so low it’ll burp and unseat on turning, it’s shaped pretty much the same. Just more or less soft. On the shop pictures some of them seem to be convex like his and others concave like mine :thinking:

#100

Yeah, and doomy’s tire is really convex at 16 psi. Something has to be physically different. :frowning:

#101

Looks like your tire has"Liwang" as a brand name. doomy’s tire looks like it says “Wanda.” Maybe they are different manufacturers?

2 Likes