Z20 - Motor or Controller Problem - w/Video

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Last seen: 15 years 8 months ago
Joined: Wednesday, December 12, 2007 - 11:53
Points: 53
Z20 - Motor or Controller Problem - w/Video

I am having issues with my Z20. It sounds and acts like it is a motor problem, but I don't know enough to rule out the controller.

If anybody could help with a diagnosis or troubleshooting tips, I would be grateful.

- Sometimes motor engages, sometimes not
- When motor does engage, big vibrations/noise from rear wheel
- Doesn't seem to want to go very fast (maybe 15mph), but I haven't tried to push it considering the vibrations and noise

The problem started during a ride on 5/16/08. I was going about 30mph (GPS) on a flat road and the Z suddenly dropped speed and significant vibrations started from the rear wheel. It seemed the bike didn't want to go more than about 15mph (GPS). The gauge indicated 80% remaining power, PakTrakr confirmed batts still had lots of charge. Immediately when symptoms started, I stopped and felt the controller and it did feel mildly hot (didn't hurt to touch, but more than warm). Outdoor air temp was 66F. The fans were not on. I let the bike sit for a few minutes to possibly cool the controller and limped back home. The vibrations occurred over the majority of the remaining 3-miles, but would occasionally stop and the scoot would accelerate and act like there wasn't a problem. After a short distance, the bike would again drop in speed and the vibrations would return.

After a full charge and letting it sit for a couple hours, I attempted to ride again to see if the problem had gone away. This time, the motor didn't engage. Later I tried again, and the motor would engage sometimes, but not others.

Video demonstrating problem:

Scooter Info:
- 647 'EVT miles'
- 263 'Real miles' (from trip logs and GPS, could be at most 20 miles more)
- Ridden 35 times, avg trip 8 GPS miles, max trip 10.5 GPS miles.
- Haven't seen a +70F temp yet, so temp shouldn't have been an issue
- Rarely ever maxed out (throttle), typical speed is 30mph (GPS).

I checked the front-end wiring, and everything is visibly OK. All electronics work. Haven't yet checked rear-end wiring (controller, breaker, etc).

This issue may have similar symptoms as described in a previous thread

iconoclast's picture
Last seen: 10 years 4 days ago
Joined: Saturday, June 7, 2008 - 22:17
Points: 11
Re: Z20 - Motor or Controller Problem - w/Video

Hi Mike,

Your problem is identical to one I'm having with my E-Max sport. TracyUSA diagnosed a similar problem as a bad motor (and fixed it) but I think these symptoms may also be caused by a bad controller or Hall Effect sensor. (As far as I can tell, my motor is OK from a teardown inspection).

I'll be happy to help you diagnose your problem if we can get some diagnostic tests mapped out. I have some test plans for unit testing, but I need to confirm these with a known good unit.

After we isolate the problem unit, if we can come up with an individual component test plan (voltage, amperage, resistance values) we can probably fix it with some very inexpensive replacement components.

Here's a link to my original post:



Last seen: 14 years 8 months ago
Joined: Tuesday, December 4, 2007 - 09:18
Points: 15
Re: Z20 - Motor or Controller Problem - w/Video

Sounds like you have a phase out in the system. There are several things that might cause this. I would first check the connections in the white connector that come from the motor. This connector holds the hall effect sensor(wheel position sensors) wires. If any of these are not making contact then you would have a symptom like what you are seeing. Its a start...

Last seen: 15 years 8 months ago
Joined: Wednesday, December 12, 2007 - 11:53
Points: 53
Re: Z20 - Motor or Controller Problem - w/Video

I'm hoping to get the time tonight to attempt voltage testing of the controller, hall sensors, etc.

I heard from EVT last week. They believe it is the controller and will be sending me a replacement as soon as they get more from China. They estimated a 2-week wait for them to arrive + shipping time to me.

usatracy over at NovaScooters believes it is the Hal Sensors in the motor. He ran into nearly the exact problem before and fixed it by replacing the sensor (something like a $3 part). He prescribed some testing to verify the HAL sensor functionality, which I will attempt.

The scooter has been out of commission for a little over 3 weeks now. Likely another 2-4 weeks before I receive another EVT controller. If that doesn't fix the problem, and I wait for EVT it could very well be 2-months before it is running again. (I'll order new parts through Nova before it gets to that)

My next EV will definitely be a conversion. If I'm going to spend all this time/money on fixing mistakes, they may as well be my own. Plus, I won't have to put up with crap components. The Z was a learning vehicle for me...so it's not all bad. However, it has made my friends and neighbors decide against an electric vehicle. They just don't want to deal with all of the problems.

I'll post an update after I do the testing.

Last seen: 12 years 7 months ago
Joined: Thursday, July 26, 2007 - 21:55
Points: 49
Re: Z20 - Motor or Controller Problem - w/Video

Hey, Mike,

I've also heard from EVTA that new controllers were coming in "2 weeks." However, I just received that message 1 day ago (the 11th). Since you were told "2 weeks" last week, I can only imagine that everybody's being told "2 weeks."

On the bright side, Andy at EVTA did mention that the next batch of controllers will be a new model. There have also been whispers that EVTA is going with Kelly controllers on their next go around. Not sure if the ones we'll be receiving will be Kelly, but I hope so.

For now, I've given up on my Z-20b being a viable source of transportation and only view it as a hobby in electronics

This board is an amazing source of info. Thanks and happy fixing to all.


Brock's picture
Last seen: 12 years 6 months ago
Joined: Thursday, August 16, 2007 - 19:27
Points: 87
Re: Z20 - Motor or Controller Problem - w/Video

That is what mine did before it stopped all together. More of a growling / jerking sound. Now that I have a new controller I know that sound isn't right, it still growls, but not like it did. Mine got a bit intermittent, then quit and never started again. When it was intermittent sometimes if I spun the wheel it would start, sometimes not.

Based on my limited experiences I would say it is the controller.

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