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[protomech]

Switched the bike on going home from work. Twisted the grip, motor would move the bike first slightly forward (4-6"), then slightly back (4-6"), then more slightly forward (~2"), then more slightly back (~2"), then stopped moving but started making a electromechanical whirring noise. (noise similar to the noise made when you push the bike while the controller is turned on, but more intense)

Power cycled the bike several times and tried again, same behavior. Tried switching it off and letting it sit for a few minutes (which had worked on the 1 earlier occasion where I saw this), same behavior. Tried moving the bike forward several inches or several feet while on, similar behavior. 

Moving the bike a couple of inches seemed to alter the behavior in that now it might move backwards then forwards before dampening a stationary whir. (adjusting phase on the oscillation pattern?) 

Next I tried waddling the bike (30" inseam) up to around 3-4 mph and cut it on. The motor seemed to "pop" and then resumed normal smooth operation, motor torque controllable by grip twist in the usual fashion, etc. 

I rode around the parking lot, then exited and rode for about a quarter of a mile and stopped in a nearby parking lot to test. Braking to a halt and then accelerating worked fine. Cutting power to the bike and switching it back on brought back the motor oscillation. Using an incline to get the bike moving then switching it on brought back normal smooth motor operation. 

Rode the bike home (12 miles), fine other than one motor cut-out. Power cycling the bike while in motion (how damaging is this to the motor? obviously not a concern if it's a choice between that and getting pasted on the highway, but if it's harmful then I'd rather avoid it) brought back the normal motor operation after the cut-out.

When I got home I switched the bike off, came back 5 minutes later and switched it back on. This time it worked perfectly, smooth motor operation. Rode out to dinner. Switched the bike on after dinner, oscillation. Waddled it forward, pop smooth motor operation.

FYI if you happen to get stuck somewhere with an oscillating motor. I think only one person in the glitch thread has mentioned a similar problem? Don't know if related but circumstances seem related.

[BSDThw]

It sounds like the SIN/COS encoder.

Did you unplug and replug the Cable of the encoder maybe there is some corrosion ...

Do you have the possibility tho recalibrate the encoder setting?

[WindRider]

I was just going to pipe in and mention that I have seen this type of behavior in industrial motors when the encoder feedback is wrong.

[nicktulloh]

It sounds like the SIN/COS encoder.

Did you unplug and replug the Cable of the encoder maybe there is some corrosion ...

Do you have the possibility tho recalibrate the encoder setting?

Just for future reference, where is the encoder plug?

[protomech]

The encoder plug is mounted on the top of the motor, tucked away a bit behind the frame. Black screw-type cap.

Agree that it sounds like an encoder error. Whether motor or controller is in error is TBD.

[BSDThw]

The SIN/COS is a special option of the Sevcon.You have to order it extra and it use some I/O /ADCs different. So it could be that it has a fault there but personally I believe more the Encoder has a mechanic or contact problem.

[expevride]

I have a very similar problem that started May 1st, really bad May 5, was unable to go from a stop, recycled then ok till 45mph then a shudder from the motor, couldn't trust it any further went home and waiting for the dealer to open Tuesday. Very annoying, was running great with no issues since they rebooted the whole system in sept of 2012. Total miles 8785.

[protomech]

I've had this happen maybe a half dozen times recently now. A reliable and easy (if embarrassing) fix is to turn the bike on, waddle it up to 3+ mph and then roll on the throttle.

[s44captain]

Protomech, what was the final answer to resolve the behavior in your bike (I ask as mine seems to have caught the same flu).

[protomech]

The motor was replaced and the controller recalibrated.

The final determination on problem appears to be faulty potting on the motor encoder.

[Justin Andrews]

Yep, this is indeed a SIN/COS encoder issue s44Captain.
If your bike is doing this, get it to your dealer. They should be able to hook it up with the cable and get the MBB to confirm that the calibration is out.

You can kinda keep the bike going by doing regular re-calibrations (as in daily) but you'd need to own the cable yourself to do that (the software is free, you just need a terminal emulator such as Teraterm)

However the best course of action is to get the motor replaced under warranty.

[Doctorbass]

I sent my motor to Zero friday and also my MBB for firmware update ( my local dealer dont have the required LOAD N GO device that do that.

I also had the impeller that was loose on the shaft making strange noise. I guess they will fix everything soon...

i'm really curious to see what kind  action they will do about poting the encoder... will they clean everything and add poting or will they just replace it.. The Loosy impeller on the shaft look like to have the hole enlarged  in the plastic so i guess they will just replace it by a new impeller..

My Zero dont have any MBB now and i can not keep the battery charged since it require the MBB... I hope they will fix everything quickly.

Doc

[s44captain]

Thanks for all the info. I'm dropping mine off for warranty. I'm very thankful for the 2 year warranty.