motor runs fine then stutters after riding for a while

This may be an easy one but I couldn't figure it out myself. I read a couple of threads about stuttering motors to find inspiration but my problem appears to be different from what I was reading about.

I have a 2012 pedal assist only izip via urbano (discontinued model).
I hadn't ridden it for many months. Now after recharging the battery, I can ride for about 15 minutes with the strongest level of pedal assist (which is the level I was always using before), then the motor has a tendency to stutter for about ten seconds before continuing normally until the problem happens again 1-2 minutes later. I noticed that if I switch to a lower level of pedal assist when the stuttering happens, it stops, but the level of assist I get is so low that it probably does not even make up for the added weight of the battery and motor compared to the effort needed to move a non-electric bike.

I'm suspecting the battery but I have doubts because when the battery was getting near to empty and was new, it would just give me reduced power without stuttering. I happen to have a spare controller, although I'm not sure whether it is good. I tried swapping controllers and the stutter-after-a-while problem is also there with the old controller. It might even be worse.

Can someone please help me troubleshoot the problem?

Check the connectors for bent pins and signs of corrosion. Unplug all of the connectors, inspect, and replug them each a few times. Replugging the connectors generates some friction between the contacting surfaces which might help wipe away any corrosion and help maintain excellent continuity. Make sure the connectors aren't bouncing around as you ride and you aren't accidentally tugging on them at some point or something to that effect, make sure there is no damage to wires anywhere along the line, perhaps there was damaged in storage.

If you haven't done so already, a little dielectric grease or boeshield t-9 will do an excellent job of inhibiting corrosion within connectors.

http://www.ebikes.ca/learn/troubleshooting.html From there, this page might help you either now or in the future.

I don't know why the battery itself would cause stuttering, but you might check the pack voltage as well as the individual cells for balance just for the heck of it.

Another possibility is corrosion inside the motor, especially if it's ever been used in the rain or kept in a damp place. The motor corrodes to make a rusty gunge over the hall sensor, which compromises it's signal. That would probably be worse when the motor is cold.

There's a picture of a rusty motor on this page where you can see the gunge over the hall sensors. It's a different motor, but it can happen on any one:

https://www.electricbike.com/9c/

Funny way of reacting to low voltage cutoff? Usually stutter is related to bad connections on motor wires, but the description of when it happens sounds to me like saggy battery voltage under load.

Expensive to find out if it goes away with a new battery though. Especially if it doesn't.

Another possibility I had happen to me. One of the three phase wires was cut, but not all the way through. Low power flowed fine, but higher power could not be carried through the last few strands left. It ran fine half throttle, but stuttered under heavy loads. So it could still be related to plugs and motor wires.

Thank you for the replies. I will use the tips you provided to help troubleshoot the problem. I hope I won't have to go as far as looking inside the motor. If the problem is the battery, I'll have a hard time finding a replacement. The battery is a unique design and the model that didn't stay on the market for very long.

If yours is a geared hub motor, it may be the freewheel has seized. Normally the small jolts from the magnets are only felt when the wheel is turned backwards, the freewheel allowing the wheel to turn without the motor when going forwards. If the internal freewheel has seized, you'd feel the magnet tugs in both directions.

clksoft said:

The battery is a unique design and the model that didn't stay on the market for very long.

Click to expand...

You don't have to use the same type of battery. If you show a photo of it on the bike and tell us the voltage, we can probably offer you an alternative that might be an improvement.

dogman dan said:

Funny way of reacting to low voltage cutoff? Usually stutter is related to bad connections on motor wires, but the description of when it happens sounds to me like saggy battery voltage under load.

Click to expand...

I had these exact symptoms when my first bike hit LVC with a cheap 500W brushed controller.