Bought a used e-bike, motor cutting off power

[Test]

I recently bought my first, used electric bicycle. It was working well for two weeks.

Today, I got a flat rear tire and took it to a bicycle shop for a quick repair. In this town I am in, there are no electric bike repair shops.

After disassembly and reassembly to get to the rear tire and replace the inner tube, the motor no longer can deliver power to the rear wheel. Since this bike shop is unfamiliar with electric bicycles, they couldn't figure out what's causing the problem.

Here's what I have troubleshooted thus far:

Upon unplugging the battery from the controller and plugging it back in, the battery indicator lights work, and power can be delivered to the headlight. A small amount of throttle can be delivered continuously without cutting power, not seated on the bike with the rear wheel not in contact with the ground. In my opinion, it sounds like a lot of noise is being generated by the motor, although I can't say for certain it is more than what it was before the tire repair.

As soon as I apply more throttle (maybe around 50% or more), the power cuts out. Turning it off and on again does not power anything (the battery indicator flashes for a very brief period, then turns off). Throttle doesn't do anything. The only way to get to the state described in the previous paragraph is disconnecting the battery from the controller and reconnecting it.

I don't have any tools to repair this bike myself, and I'm very new to electric bikes. I would simply like to return to the bike shop with suggestions on how to fix the new issue (edit: I didn't want to imply they broke something on purpose).

Anyone have any suggestions?

Thanks for reading!

 

[Test]

What bike is this?

Why would you unplug the battery and controller just to change rear tire and tube?

This is the used bike I purchased: https://electrobike.com.mx/productos/bicis-electricas/dash/dash

The mechanic that fixed the tire didn't unplug the battery from the controller.

I only described myself doing that trying to troubleshoot the problem as to why the power cut off after the tire repair. After the tire repair, no power was being delivered to the motor. I brought it back to the shop to see if they had an idea what caused this new problem, and they said they don't know as they don't deal with electric bikes.

The only way I know to get power back to the headlight, the battery indicator and the motor, is to unplug the battery from the controller, wait a minute, and then connect them again. Turning the key from off and back to on doesn't work. When the power is being supplied, as soon as I apply too much throttle, it cuts off.

I am just looking for possibilities I can ask the mechanic to try tomorrow as I have no tools to fix it (and don't plan on buying any because I don't live in this town, just visiting for several months).

Thanks for your help!

 

[Test]

Is your motor connector plugged in tightly?

Yes, it appears to be plugged in well at the rear axle. I can give it low throttle with no rear wheel resistance and the power stays on.

I uploaded a video of the problem. The noise right before the power cuts off is definitely noticeable here as I gradually increase throttle.

Odysee

Explore a whole universe of videos on Odysee from regular people just like you!

odysee.com

 

[rich c]

Did you also post on reddit? On there I suggested you check the washer and spacer position to make sure the motor axle is not in a bind in the frame. Also don't expect that they broke something. That will stop any service you may have wanted in the future if you go in with an attitude and will give the LBS another reason to never allow an eBike in the shop. People on here wonder why shops won't work on their eBikes!

 

[Test]

Did you also post on reddit? On there I suggested you check the washer and spacer position to make sure the motor axle is not in a bind. Also don't expect that they broke something. That will stop any service you may have wanted in the future and will give the LBS another reason to never allow an eBike in the shop. People on here wonder why shops won't work on their eBikes!

I didn't post anything on Reddit.

On there I suggested you check the washer and spacer position to make sure the motor axle is not in a bind.

This sounds very much like a possibility I can suggest to him, as when I was watching him fix it, he appeared a bit confused with the order of washers when reassembling the rear axle. We can try to double check the washers and spacers.

Also, I didn't mean any ill-will towards the bike shop. Technically it did break after the tire fix, and perhaps the way I worded it made it sound like it was unexcusable. It was an accident I'm sure, which is why I'm not hesitant to go back there again for another emergency or a tune up.

Does it make sense logically then because of poor washer/spacers that the controller will turn on circuit breakers when too much throttle is applied?

Thanks for your help!

 

[Test]

I'll also add that if I manually pedal at the same speed or faster than when the power cuts off using just the throttle, that loud noise as was shown in the video is not present.

 

[Test]

New observation: I can get it to full throttle if I add throttle very slowly.

Anytime I increase the throttle significantly and suddenly, the power cuts off.

It's sounding a lot like this problem described on another forum: https://electricbike.com/forum/foru...hrottle-quickly-the-power-cuts-off-help-pleas

 

[PedalUma]

The connection from the controller to the wheel is faulty at the left rear chain stay.

 

[indianajo]

This is a rear hub motor bike. What kind of connector(s) connect the motor to the controller?
The 6 pin white rectangular block for the hall effect sensors, can get the pins bent when plugged back together. Pry back the latch with a screwdriver, pull apart, and inspect for that. If one is bent, you can bend it back straight with small pliers.
If the blade in the white connector got broken, I bought a supply of them on e-bay. However, the last time I looked they were gone. Name was "ebike scooter connector".
If the 3 motor wires get plugged in the wrong order, the motor will start backwards. Usually blue to blue, green to green, yellow to yellow. Some controllers use screws & ring terminals on a block.
If you have the 9 pin round connector to the motor, my sympathy. They are so small they can short out in the rain. I cut mine off and replaced with with the white rectangular one, so I don't know what else can go wrong. I suppose it could be plugged in the wrong way with enough force.

 

[Test]

Thanks for the input all.

We ended up taking apart the housing of the controller and just verifying all the connections. When the controller was tilted sideways the problem was no longer there, but when in the vertical position, the problem persisted. Seemed like magic. With some scooting around of wires so far the problem has not come back, but it seems like a really fragile fix not knowing for certain what the culprit was.

I'm probably going to invest in a pair of pliers and a screwdriver to investigate when the problem arises again.

 

[harryS]

Before you opened the controller housing, did you recharge the battery? The problem sure sounded like a weak battery to me. I experiment a lot with various batteries, and have come across those symptoms when a battery needs to be recharged.

Nonetheless, glad you have a resolution to the problem.

 

[Test]

Before you opened the controller housing, did you recharge the battery? The problem sure sounded like a weak battery to me. I experiment a lot with various batteries, and have come across those symptoms when a battery needs to be recharged.

Nonetheless, glad you have a resolution to the problem.

Yep, the battery was fully charged at the time of that video in my earlier post. It was also near full charge at the time of fiddling around with the controller and wiring. I suspect some bumpy roads may put it back into its former state, but time will tell. So far it survived the trip back from the bike shop.

 

[harryS]

Probably a pinched power wire then, down to a few strands of copper. Can't carry full current when bent.

 

[PedalUma]

Probably a pinched power wire then, down to a few strands of copper. Can't carry full current when bent.

If this is the problem it will need to be spliced. If something is loose inside the controller a dot of hot glue may do the trick.

 

[Test]

The problem came back after a ride yesterday.

The rear wheel is noticeably stiffer and not spinning as freely as it did before (as was shown in the video). Applying throttle I hear a much longer grinding noise (as was heard in the video), and then the power cuts off.

Is stiffness in the wheel normal when hooked up to the motor?

I bought some tools to try to figure it out myself now.

 

[PedalUma]

Now it needs wafer thin washers. I do not like hub-drive bikes. Stay away from them.

 

[john peck]

I recently bought my first, used electric bicycle. It was working well for two weeks.

Today, I got a flat rear tire and took it to a bicycle shop for a quick repair. In this town I am in, there are no electric bike repair shops.

After disassembly and reassembly to get to the rear tire and replace the inner tube, the motor no longer can deliver power to the rear wheel. Since this bike shop is unfamiliar with electric bicycles, they couldn't figure out what's causing the problem.

Here's what I have troubleshooted thus far:

Upon unplugging the battery from the controller and plugging it back in, the battery indicator lights work, and power can be delivered to the headlight. A small amount of throttle can be delivered continuously without cutting power, not seated on the bike with the rear wheel not in contact with the ground. In my opinion, it sounds like a lot of noise is being generated by the motor, although I can't say for certain it is more than what it was before the tire repair.

As soon as I apply more throttle (maybe around 50% or more), the power cuts out. Turning it off and on again does not power anything (the battery indicator flashes for a very brief period, then turns off). Throttle doesn't do anything. The only way to get to the state described in the previous paragraph is disconnecting the battery from the controller and reconnecting it.

I don't have any tools to repair this bike myself, and I'm very new to electric bikes. I would simply like to return to the bike shop with suggestions on how to fix the new issue (edit: I didn't want to imply they broke something on purpose).

Anyone have any suggestions?

Thanks for reading!

My guess is they screwed up the connector pins taking off the wheel. Do you get an error code on the
display. How about modes can you still change them? Being an emerging industry trained repair is
not to be found outside of urban areas. It behooves you to learn all you can here & from tutorial
videos, Then too it´s wise to have a few basic tools.

 

[Test]

My guess is they screwed up the connector pins taking off the wheel. Do you get an error code on the
display. How about modes can you still change them? Being an emerging industry trained repair is
not to be found outside of urban areas. It behooves you to learn all you can here & from tutorial
videos, Then too it´s wise to have a few basic tools.

This bike just has the basic battery level display and nothing else.

It logically would have to do something connected to the wheel since everything went downhill after the inner tube replacement. The connection to the motor was never severed during the repair, but seeing this is a used electric bicycle, there are some parts of the wire that could be frayed on the inside as Timpo pointed out, and the reassembly could have dislodged some sort of temporary fix that was applied to the wire or connection.

As to the most recent problem of a stiff wheel, I think I fixed it adjusting a small screw on the drum brake. I balanced the rear wheel as well with some bolt adjustments, but I don't know how my weight on the bike will affect both fixes. Will have to test it out tomorrow. But now the wheel spins freely.

Does it seem plausible that because of brake rub that the motor could signal to the controller to cut power because of excessive power demand? I know there are issues of other electric bikes cutting power when climbing hills, so curious if this is a similar scenario (which I hope my drum brake fix also fixes).

 

[harryS]

Try this. Power is off. Lifting wheel, does the wheel spin forward and reverse? SInce it's a geared motor, you will feel the resistance from the gears in reverse, but it should still turn, Then with power on, repeat this test. Does it spin the same in reverse? If the wheel seems to lock up in reverse with power on, there's a circuit problem..

The above is a simple test to see if your motor has a short cicuit. If it locks up with no power, the problem is in the cable or motor. If it locks uo with power, it's in the controller.

 

[Test]

Try this. Power is off. Lifting wheel, does the wheel spin forward and reverse? SInce it's a geared motor, you will feel the resistance from the gears in reverse, but it should still turn, Then with power on, repeat this test. Does it spin the same in reverse? If the wheel seems to lock up in reverse with power on, there's a circuit problem..

The above is a simple test to see if your motor has a short cicuit. If it locks up with no power, the problem is in the cable or motor. If it locks uo with power, it's in the controller.

Wheel spins both forward and reverse, with resistance in reverse. With the power on, it behaves the same with the same level of resistance as with the power off. So hopefully it's just a cable problem, as I wouldn't be keen on trying to fix or buy a new motor.