Transferring this discussion from "Test Ride of the ZEV Scooters," which became a mash-up of various ZEV topics. (I think ZEV deserves a folder here, like other brands.)
The problem: I'll be riding my ZEV S-8500 in any throttle position, then there's a complete loss of power (motor cuts out) until I zero the throttle for a second and twist again. Since this sometimes coincides with riding over a bump, I searched repeatedly for loose/faulty connections. But it doesn't seem to be a simple power interruption. When the bike is apt to do this, it starts rougher (hesitates a bit) from a stop, and there's a quiet growling or groaning sound, from the hub I think, especially when first accelerating. Other times when it accelerates smoothly and quietly, the cutting-out is rare or absent. I used to think a fresh charge made it run better, but that is no longer true. The scooter comes right off the (new) charger now, rides normally for a block or two, then starts cutting out like crazy, multiple times each block.
I bought the scooter from a guy who had it a year and put 600 miles on it. He reported no such problem, but I can't vouch for his honesty. It has a Cycle Analyst (not with throttle control) and an upgraded ZEV 180 amp controller, the former installed by ZEV and the latter by the owner. The included charger went dead in mid-August and I bought a new one, the latest model, from ZEV. Interesting factoid: The cutting out disappeared completely for over 2 weeks when I started using the new charger — I thought the problem was solved. Then for no apparent reason it returned. The new charger seems to work as designed, with an (initial) 12 amp bulk charge, then eventually top-balances with a fraction of an amp. The bike's resting voltage after this is about 101.5, but it immediately drops to about 96 as soon as I start to ride, and stays there. The Cycle Analyst shows no sudden voltage drop when it cuts out, and Vmin is in the mid-80s.
Here's what I tried so far without effect:
- Both brake micro-switches and the side-stand switch are disconnected.
- I repeatedly inspected, and shot with aerosol contact cleaner, all cable connections and small wire connectors behind the dashboard and under the seat, plus the 24-pin connector on the controller. All battery and circuit breaker connections are tight.
- I confirmed constant voltage from the key switch to the controller, including when I jiggle wires and bounce the bike up and down.
- With the bike running on the center stand, I was unable to make it cut out by handling/jiggling wires behind the dash or under the seat. Or the key in the key switch.
- On two separate occasions I measured all cell voltages when fully charged, and again after running the batteries down to where the controller stops the motor. Both times the fully charged cells were all close to 3.34. The first time I found two discharged cells with voltages around 2.8 as compared to about 3.1 for the rest. I charged them individually, bottom-balanced the pack, then fully charged as usual. The cutting out still happened. The 2nd time, all discharged cells were between 3.04 and 3.13. I didn't bother to bottom-balance, and just charged as usual. The cutting out was bad as ever.
Darus Zehrbach at ZEV walked me through most of this, and I sincerely thank him for trying to help. However, his simple/brief suggestions often result in hours of frustration for me. For example, it sounds easy to remove the plastic covering from the handlebars to trace the wires from the throttle, kill switch, etc. I twisted and squeezed and pried and swore until I finally started breaking off the plastic tabs on the covers, so I gave up. I also spent many hours several weeks ago removing the top row of batteries, unnecessarily it seems. There's apparently no wiring diagram or service manual, and I'm still fairly new to EVs, so nearly every step means either guessing or emailing Darus, or both. I'm hoping others here recognize these symptoms and can point me in the right direction. In particular, I think the only possible culprits I haven't checked/tested yet are the BMS and controller themselves. (And maybe the Hall sensor?) Are there any tests I can perform with a multimeter on these components? I assume swapping out controllers is expensive, I haven't really checked. Is there a bad ground wire I may have overlooked?
This has been incredibly frustrating, and I don't mind saying I very much regret the purchase. On the other hand, if I ever get it working reliably, this scooter would be just about perfect for my intended use. Thanks for your suggestions and insights.