E-bike motor pulses when I go from a full stop to a full throttle.

[JoeS]

Hey guys and gals,

I bought a used Watseka e-bike 36v 250w 9ah battery color is black.

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Price: $649.00 | Model Year: 2016 | An ultra affordable electric bike sold on Amazon for ~$650, requires 1.5+ hours for assembly along with some basic tools (it comes with a few unique wrenches and instructions to get you going), the kickstand is two-sided and very stable which helps with setup

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Checked it out with a Romai controller tester and it showed it needed a new controller.
Tested motor and Hall Effects Sensorsthey tested as they should as well as did the main phase .
Tested new controller and it passed with flying colors.
Tested twist throttle shows to be work according to Ronai tester.
Battery shows 38.5v.

I replaced the controller hooked it up to battery.

Turned throttle all the way open and rear bike wheel turns but pulses, lets say ever second or second and a half.
if I back off on the throttle and slowly advance the throttle it will slowly pick up momentum and I can then s l o w l y advance the throttle and the motor will pick up speed till the motor reaches top speed.
​

Once back tire is spinning ​

at a good rate I can go on and off throttle no pulsing no hesitation.

If it was an old school car I'd say it has a sticky choke or maybe trying to vapor lock or weak fuel pump but alas, it's electric and not a gas engine.

Wonder what is causing it to pulse when I open the throttle up to the maximum when starting out from a dead stop.
Why does it work if I slowly twist the throttle feathering the power from no throttle to max throttle?

Things that make me say hmmm?

Thanks

Joe in Florida​

 

[harryS]

FIrst question is did the Watseka ever work for you? DId it break down or did you buy a non-running ebike?

These testers are nice for checking motor hall/phase, but I don't know that they're that good for controller testing. Mine has six LED's in a ring, and they spin around once with a working controller. The patterns differ if I mix the Hall wires colors, instead of matching them. You would think ideal is the pairs go in sequence, but I only get that if I miswire it. If I mix the phase wires, the pattern switches from paired LED's to opposite LED's and it spins the other way,

I've never found any instructions that tell what pattern to expect, so without that, all I know is that the controller is powering the phases and reading the Halls, but I do know how mine works with a good controller (I have several spares).

The main reason controllers don't start the motor is because the phase/hall wires are mixed up. I've seen five or six different brands of controllers, maybe four different motor makes, and never had a problem connecting phase/halls by matching the colors. Other people say the manufacturers use arbitrary coloring, but for me, so far so good.

 

[PDXzap]

Have you tried it with another battery?

Wonder what is causing it to pulse when I open the throttle up to the maximum when starting out from a dead stop.
Why does it work if I slowly twist the throttle feathering the power from no throttle to max throttle?

This symptom could easily be explained by a weak cell(s).

 

[steve marino]

I very much suspect the hub motor. Know you don't want to hear that. If you have a new controller and a fresh battery, I would suspect something in the hub motor, even if the test showed ok. There's not much left after verifying that the first two things I mentioned are working properly. I had a bike that acted very much like yours. It would run, then shut down. If I very slowly gave it throttle it worked and ran fine, but as soon as I stopped it started acting up again. Didn't know how to ck the hall sensors, didn't want to dig in there and replace them in any case, so I bit the bullet and changed out the hub motor and that fixed it.