Can over-spinning a small wheel cause over-volt problems?

D

darkmunk

10 mW
Joined
Apr 13, 2020
Messages
33
Location
Plymouth
My slow EV to fast EV moped conversion is going reasonably well, with some teething problems.
It now has a Sabvoton 72150 and 20s7p pack and it goes like a little rocket.
However, at the end of a fast section after closing the throttle, the Sab' cuts out and needs rebooting.
Is this a common problem?
My speedo doesn't work, but I seem to be doing 35 - 40mph down hill; the original moped was governed to 26mph max.
Are my little wheels, now travelling 30% faster, causing some over-voltage situation on overrun and tripping the controller?
I've tied all sorts of settings but nothing works. The only think that seems to be consistent is the speed at which the problem occurs.
I'm charging the battery to 84v at the moment (haven't worked out how to stop it at 80v), but the problem persists even with only 72v left in it.
 
If the motor's generated voltage at the speed you're going is higher than the battery voltage by enough to trigger the controller's HVC, or even go over it's hardware's capability to handle, you can get various problems.

Does your controller log data such as battery or regen voltages? If so, you might be able to find out if tha'ts the case.
 
I don't think it does write a log.
Tonight, I'll try connecting the brake cutout wires, maybe that will help isolate the return voltage.
 
Well, you can still use a voltmeter on the controller/battery connection, and read what it says just before it cuts out, and just after. It's just tougher because you have to also watch out for road conditions, traffic, etc., at the same time. :(
 
I used to have overvoltage error withy Sabvoton but it was seldom therefore I never looked for true reason behind it. I would reboot the controller on the go with ON/OFF key on my scooter, it takes about 2 or 3 seconds (plus reaction time); might put one in dangerous situation especially if road is busy with traffic or on takeover maneuver. I think I noticed overvoltage error would occur after I hit pothole or similar thing on a road but sometimes it would happen after full throttle.

(error on some other bike...)
Very recently we got overvoltage and some other error which was caused due bad connection in stock connectors, these white CN connectors which come stock with the controller. These errors again started to appear after full throttle test ride and accidentally hitting pothole and some manhole covers. Initially looked like hall sensor broke inside motor but it was found that CN connectors lost good connection/contact.
 
Ah yes. The connections are still a bit temporary, so that’s worth remembering.
But the cutoff is always after a fast section, after shutting off.
 
Seems to be getting worse. Virtually every over-run situation (shutting off) causes it to shut down.
Thanks for the software Minde. I managed to turn on variable regen, but as soon as I went back to the mobile app, variable regen vanished again. The PC software seems to have made the motor rough, but that's almost certainly something I did.
I wonder if setting the peak phase current back up around 300A instead of 180 would do it...
At work now so I'll just have to wait..
BTW, I assume variable regen is not actually regen? Is it actually using battery power to add a reverse torque?
 
Well I tried increasing the max phase current to 300A, but that made no difference.
All the connections are good.
I've tried every permutation of e-brake and regen.
I've tried running the battery down.
I've tried all sorts of setting including no field weakening so it doesn't go too fast.
Nothing has worked yet.
My battery is 20s7p with no BMS.
The moped goes really well. It's an absolute hooligan :) It's just this one glitch, ruining it.
It's still a bit rough on the overrun even with no regen or braking. Then it cuts out and all goes smooth.
 
Tried with and without a resister on the temperature wire, just in case there was a glitch in the software. But it still cuts out.
The other day I had everything set to max fun and was doing about 40mph (no speedo) and when I shut off it didn't just cut out, it locked the back wheel for a second then let go. Luckily all these events happen after shutting the throttle so it's just annoying.
Anyway... it really does seem like too much speed in the little wheels. I may have to go back to the original controller and just make a mental push bike with this one.
I wonder if there is a way to just cut the connection to the controller when I shut the throttle, so that no voltage spike gets to it.
Like a one way valve (diode) on the phase wires? or something.
Come on gang! there must be some electronics whizz who knows how to do this? :)
 
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