e-bike motor won't spin after getting it back from the LBS

[Mark Stosberg]

I need some some debugging help.

I recently got my wife's electric Yuba Mundo back from the bike shop after they put some new tires. I know and trust the bike shop folk, but they don't have e-bike experience. The mechanic said he test drove the bike and loved how it rode with assist. I presume he did that /after/ he put the new tires on.

When I was riding it home, I notice the front fork with Nine Continent front hub motor was vibrating badly when the throttle was engaged, but I assumed the issue might be transient. The bike was built in 2010, and there have been various hiccups along the way that seemed to self-recover, and I thought this might, too.

Once I was home about 3 minutes later, I inspected the front more closely to see if anything seemed amiss. I found a couple things.
The hub motor has small torque arm that connects back to frame to help hold the wheel in place. The nut was missing off the back of the bolt there, and the bolt was going through the whole at an angle instead of straight.

Also, the hub has a small bar next to it that usually points straight down. It was about 20 degrees off. The bar can be seen here in a photo pointing straight down, pre-repair:

https://farm9.staticflickr.com/8379/8681520811_9eed95e9e8_o.jpg

I reproduced the bad vibration issue for my wife at home, but soon after that, things got more "interesting". The hub quit turning at all when the throttle was engaged. I'm not sure if this related to the vibration issue or not.

Here's what I've done so far to diagnosis why the hub isn't spinning:

• I used a multi-meter to confirm that the battery is working. It's putting out about 39 volts, and it's a 36V system that works from about 42V to 31V. I have a 15Ah LiFePo4 battery.
• I have a Cycle Analyst, and it also reads 39V.
• If I unplug the hub motor and test the DC voltage arriving at the hub, it's just a trickle-- millivolts. The wires are blue, yellow, and green. I'm not sure what's what, so I just checked all the combinations.
• I have an Infineon 35A controller. As I looked it closely, I did find the connection to the hub was loose and tightened it, but that made no difference.
• Next, I used the multi-meter to check the voltage coming /out/ of the controller headed towards the hub. Again, the wires are blue, yellow and green. Again, I just see a trickle of millivolts there, with and without the throttle engaged.

From my multi-meter tests so far, I'm concluding that there's a problem with the controller, since the battery has voltage out to the controller, but the controller has no voltage out to the hub. How could this be related to the vibration from earlier or the loose connection I found? Are they all related, or all there multiple issues going on here?

For an additional test of the hub, I thought of connecting it directly to a battery source to confirm that it spins with juice applied. For that, I will need to be a little more careful to make sure I don't get my wires crossed.

Sound advice and wild speculation are welcome.

Thanks,

Mark

 

[bowlofsalad]

I don't take my bicycles to any LBS any more, I've never really found a place (I've tried several) that had an acceptable level of competency. And I was often met with a level of disgust or arrogance concerning ebikes, like I was an absolute retard for thinking ebikes are a good idea. I mention this after hearing about the way you got your bike back in return, sounds very incompetent, scarily so.

My guess is that there is something wrong with one of the plugs, I'd focus on the one relating to the halls. I'd check the pins and wires, I am a little worried the wrench monkey who messed with your bike gave a cable a hard yank when trying to remove the wheel, forgetting/ignoring the plug. Worst case scenario is you have to open the motor up to resolder a connection, best case scenario might be a bent pin or something just a little loose.

Please don't take this the wrong way, but removing and installing tires is a pretty easy task, and something you should probably jump at the chance to practice. Consider it a chance to work on your technique in the occasion that you get a flat and need to fix it on the side of the road.

 

[DAND214]

As above post I take it's a sensored hub. Power to the motor directly from the battery will not run the motor but could also damage it.
Vibration could be a loose/bent or backed out hall connection. Check if the colors are matched at the hall connector or two crossed. If so you will need to match them when you hook up the phase wires.

I would be very concerned about the miss installed wheel. If the tourqe arm isn't alinged properly, it indicates that the wheel isn't in right.

Dan

 

[teklektik]

I'm thinking you may have two problems:

1. spread dropouts or damaged axle
2. damaged motor wiring

With a suspected axle issue and the LBS pulling the wheel with wiring, I would suspect the motor wiring rather than the controller - which was safely strapped down to the bike. This is not to say that the controller might not have taken a hit later as a secondary issue, but it's not a place I'd start.

The hub motor has small torque arm that connects back to frame to help hold the wheel in place. The nut was missing off the back of the bolt there, and the bolt was going through the whole at an angle instead of straight.

Also, the hub has a small bar next to it that usually points straight down. It was about 20 degrees off. The bar can be seen here in a photo pointing straight down, pre-repair:

I'm guessing that the 'small bar' is the green circle item?

It sounds like the LBS didn't understand the 'torque arm' concept and didn't re-attach it properly (missing nut and bolt that failed to properly anchor the TA). This allowed the axle to rotate in the dropouts. The 'new' angle of the bar thingie is an indication that the axle has rotated. This most likely either spread the dropouts or trashed the axle. In either case - don't ride this until the suspected rotation has been investigated and resolved.

When I was riding it home, I notice the front fork with Nine Continent front hub motor was vibrating badly when the throttle was engaged,...
...The hub quit turning at all when the throttle was engaged.

The vibration was probably an inoperative phase. Because you were rolling, the remaining phases ran when they could. Once you stopped, either things got more damaged, or you have stopped on a dead phase and it won't spontaneously start (You can try lifting the front wheel and giving a little throttle while you spin the wheel to get it started. If it spins up, then you have an inoperative phase.).

In the picture, the harness appears to have a solid block of connectors so getting the phase wire order fouled up is unlikely. I suspect the wiring is damaged and you have shorted phase wires. This might happen either because:

• The LBS flopped the wire around when they were working the tire and caused a short, or
• the twisting or damaged axle also damaged the wiring as a trickle-down casualty.

So - all this is speculation, but that's a knee-jerk evaluation - (being wrong would be Very Good...)

Dropouts/Axle
I would recommend removing the axle nut on the non-wiring side and examining the axle and dropout. Ideally the axle flats are a nice snug fit into the 10mm dropout and the dropout looks like a clean parallel slot. If you don't feel comfy with this inspection, post a close-up with the nut off. If the dropout slot is spread (V-shaped) or the axle looks mangled, then replacements may be needed. If the issue/damage is small, you may be able to get away with re-seating everything or perhaps adding an additional torque arm on the other side to reinforce the situation.

• BTW: The nut only needs to be 'pretty snug' when you re-assemble this - don't go crazy with a long handled wrench and really crank it down - these axles are often of low quality steel and stripping them is a possibility.

Wiring
First go for the easy one: separate the phase (3 big wires) and hall (5 small wires) connectors and inspect the pins. All the pins should be the same length. Sometimes they get pushed back out of the shroud and fail to make connection. If so, push the pins back into place from the back of the housing. Re-connect and try again. With luck - all will be well.

If not, then with the bike powered off, unplug the phase wires (heavy R/G/B wires). Spin the wheel - it should spin freely. Next use a short bit of wire or a paperclip to methodically short the R/G, G/B, and B/R motor wires. In each case spin the wheel and it should have drag - the drag should be the same in each case.

• Here we are using the motor as a generator running a dead short which requires noticeable effort to turn, vs 'no-short' which should spin easily.

If the 'free spinning' and drag don't work out this way (i.e. the 'no-short' case is not free-spinning, has similar or more drag than a 'shorted' case, or one or more shorted cases make no change), then you likely have shorted wires.

You can also use your meter to test continuity between each phase wire and the axle. There should be no continuity. If there is, then there is some wiring damage.

There's other things to test, but this should get you started.

FWIW - If you are going to have a non-ebike LBS fuss with your wheels, I might recommend that you remove the wheel yourself. Leave the torque arm in place with the axle nut and zip-tie the wiring to the TA so it can't flop around. Not the best situation in any case, but...

 

[dnmun]

yep, the mechanic could be so dufous he drove it without the torque arm installed properly and spun the axle in the dropouts.

does the wire look like it has wrinkles and twisted.

 

[dogman dan]

Likely it cut a wire where it goes into the motor. It could be a phase wire or a hall.

If you are lucky, the problem is actually in a plug, since the shop did unplug the motor to do the tire I bet.

You'll need to get in the habit of doing a closer inspection if they touch your bike. What action to take now depends on you and the attitude of the bike shop. They owe you something, but much depends on if you would like them to hate you in the future. Get them to give you some free service rather than cash makes sense to me. But maybe just service that never takes that wheel off again.

 

[Mark Stosberg]

Thanks for the all the replies!

It appears I didn't get automated notifications for any after the first so I just found them now. Thanks so much for the suggestions. I'm going to act on the feedback here and will report back the results!

 

[Mark Stosberg]

The diagnosis that that one of three phases was out of commission appears correct.

I closely inspected the 3 Anderson Powerpole connectors near the wheel. One pair was slightly melted near the connectors and the connectors were darkened. Not good!

I found that I have some spare Powerpole connectors. As a first course of action I'll work on replacing the damaged Powerpoles and see what that does. I'll let you know.

 

[BikeFanatic]

I bet the one phase connector was not seated well, sometimes and anderson pin can back out some, I always find I have a loose phase connection when my motor stutters. This is the best case senario, you only have to replace the andersons on that phase wire. good for you.

Also as others said I would be very careful letting the bike shop unmount and mount my hub onto the bike, since they have so little experience, they could easily spin the motor in the dropout and damage your wires.

good luck.

 

[teklektik]

I found that I have some spare Powerpole connectors. As a first course of action I'll work on replacing the damaged Powerpoles and see what that does.

Excellent news! Replacing the plastic shrouds is annoying but quick. No need to replace the blade unless it's badly burned/pitted.

How did the dropout inspection turn out?

 

[999zip999]

If it is not working then don't hog down on throttle if not working. Take it ez on the throttle till.you get it working right.