MAC 7T Hall's busted, replaced x2 , removed PCB, video incl.

[cal3thousand]

BUSTED:

So on the very last leg of my wife's long overdue bike build, I plugged the CA-DP wire into the Hall connector of the motor accidentally. Yes, I know the controller has a 6 pin JST and a hall should only have 5. But on this motor, a temp sensor has been installed by the factory and another wire comes out, so I put a 6 pin on there. (Apparently, I wasn't the only person to have made the same mistake http://endless-sphere.com/forums/viewtopic.php?f=2&t=31775)

The motor would not run and just made a noise like it wanted to run. Holding the wheel and pushing it backwards slightly and hitting throttle made the motor jump a tiny bit and then nothing. Per the other thread's conclusion, I knew it was the halls.

Having never done this before, I contemplated everything from swapping the motor to a HS3525 I have on had to sourcing a new stator for the MAC. But I'm cheap, so I figured I could fix it.

I tested the halls with a DMM while spinning the MAC backwards and 2 of the halls were showing nearly 5v and never dropped. Having some hall sensors on hand, I decided to give it a try. Did my best to remove the epoxy and not damage the windings with a heat gun and pick. Cleaned off the PCB, soldered 3 new halls onto it. (I didn't know which order to do it and thought this would give it the best alignment). Then I glued everything down with DP420 and waited for it to dry. Reassembled the motor to test.


REPLACED:

Now, I get a growling noise from the motor, but it doesn't turn. I made sure to test the PCB traces to the connector end for continuity on each leg. But I also reused the capacitor from the PCB without thinking. So I have a big suspicion that this is the culprit. I haven't tested the halls on the motor as it was getting late. Will do this tonight.

STILL NEED HELP:

Do you think I goofed by not replacing the cap? Or could it be a hall alignment issue? (I'm not sure I had them where they were supposed go exactly since the epoxy made it hard to precisely tell). I know that I need to do some more testing tonight (Got too late last night to finish), but I wanted to see if anyone had a good answers or tips based on experience so I can go back with a more focused attack.

Here's some photos of the situation: ( I know we love photos )

Before the repair attempt (notice the cap(?) on there) :


The halls are in place, trying out alignment, about to solder


Traces/wiring tested for continuity, everything glued down

 

[cal3thousand]

Bueller!??!?!!??

 

[cal3thousand]

Ran out to the Radio Shack and grabbed a new capacitor (10^4 pico F = 0.01 µF) but the only one they had was rated 50V and was much larger. Oh well, put it in there and I got a new noise from the motor:

[youtube]cGukrhdU95s[/youtube]


Yay? :? It's better than the previous noises, so we're getting somewhere I hope


So, I got the idea to grab my sensorless controller off of my other bike and test things out. The sensorless would run the motor backwards at first. Then I toggled power on/off and it ran forwards like I wanted. So at least I know I'm putting this thing back together properly each time, I just have to get the halls correct. At this point, I read some information about how halls really worked and came to the conclusion that I had not aligned the halls correctly. If the halls are supposed to read relative position with a magnetic field, their distances from the magnet ring need to be as similar as possible and my previous attempt was anything but precise.

I looked at some pictures and videos and noticed that the BMC motors had their halls mounted on the side of the stator with the top of the hall sensor at the edge of the 'ring'. That puts the halls equidistant from the magnet ring and within it's field. (If I let go of the hall at this location, it would get pulled to the magnets and stick.) I tacked each of the 3 sensors in between the stator gaps with Super Glue and confirmed that they were each located at a different section of a magnet i.e. one was at one pole, one at another, and one in the middle of a magnet.



I also got to making a small harness of 3 pairs of wire on a parallel circuit with a new .01µF 50V Cap for the + and - Hall sensor leads and partially soldered them in before bedtime. After work, I get to solder the rest in and glue it back down. Hopefully, I get to deliver a bike to my wife soon.

Am I doing it right?

(BTW, DP420 just falls apart with some heat and a pick. I did not expect that at all. For you guys relying on this stuff to hold on your TAs without fasteners, I hope your dropouts don't pick up too much heat from the axle. )

 

[cal3thousand]

So, I got to buttoning the thing back up and testing it....

and I failed.

It doesn't even move now. It made a thud noise once like it tried to go and then nothing. This hall tester that I have is also not cooperating with me (the connectors are not the same position as other ones I've seen and I can't read chinese), so I will have to rig up a testing circuit with some LEDs before this motor can be fully fixed.

I think I'll just throw a sensorless controller on there and cry for a little bit (j/k). I really need to get this bike moving and that will be the quickest way. I guess I will revisit this thread and repair at a later date. :x

 

[drummerian]

I am also having this same problem! Please keep us updated if you progress

I am waiting on my halls to arrive to replace. One is definatly not working.

 

[cal3thousand]

I am also having this same problem! Please keep us updated if you progress

I am waiting on my halls to arrive to replace. One is definatly not working.

Will do.

I have Paul (cell_man;em3ev) sending me a PCB and halls. I also ordered 3mm shrink and some 10AWG cable to do the upgrade while I'm at it.

In the meantime, I have located a new 8T from Toronto that I hope to get here soon. That way, the 8T will go into this bike (quick stator swap) and I can work on the busted 7T stator and lace the other housing at the same time. We'll have more news on Monday hopefully.

 

[drummerian]

I will try and replace my hall as soon as I can. At least you got a few years of use out of yours before it broke!

 

[John in CR]

The only motor I've ever had with a hall problem, it originated from the insulation on the hall wires getting hot enough to cause a hall wire short. Mine was especially hard to find because in only started to short once the motor got up to operating temperature. Even if quality wiring is used for the phase wires, the same may not be true for hall wires. Halls are quite dependable items, so the rate of failure around here is unusual. If you have a hall failure the cause should be addressed, not just replacement.

Also, hall orientation of the center hall can be an issue as they center one is upside down on some motors.

Last, get that tester working. The hall plug is in the standard arrangement for the +5v and ground.

Good Luck!

John

 

[cal3thousand]

I will try and replace my hall as soon as I can. At least you got a few years of use out of yours before it broke!

I didn't even get a mile on the road before this broke. Stupid accident during the build.

I paid a member here for the 8T and I have been riding this thing on a sensorless Lyen 12FET. Just have to baby the throttle on take off until about 15 mph.

The only motor I've ever had with a hall problem, it originated from the insulation on the hall wires getting hot enough to cause a hall wire short. Mine was especially hard to find because in only started to short once the motor got up to operating temperature. Even if quality wiring is used for the phase wires, the same may not be true for hall wires. Halls are quite dependable items, so the rate of failure around here is unusual. If you have a hall failure the cause should be addressed, not just replacement.

Also, hall orientation of the center hall can be an issue as they center one is upside down on some motors.

Last, get that tester working. The hall plug is in the standard arrangement for the +5v and ground.

Good Luck!

John

I wonder if the wires in mine are shorted or if it is just my poor installation technique. I will mimic the 8Ts hall locations after I crack it open to swap stators.

On related news, I got the ebike tester out and the negative post on the 9V battery was corroded. Gonna scrape it off and get this thing working.

Thanks!

 

[drummerian]

Thanks for the update.

Any chance you can photograph the angle of the halls in the 8t just so I can compare mine. Thanks in advance

 

[drummerian]

I have now managed to fix my motor with new halls. Hope I can help if needed

 

[cal3thousand]

I have now managed to fix my motor with new halls. Hope I can help if needed

Nice!!! congrats.

I got busy this weekend with Ikea, so the bike didn't get much love. (In-laws are coming this week and we need to get the place in order)

Another interesting thing this weekend though. I hooked up the ebike tester to the motor and the halls lit up. I'll get a video together to see if they are really working in order; but it seems as if my repair actually go halls working to send signals back. Now to test the controller too to see if that was the issue all along. I'm neck deep in crap for the next few days, but I will be off starting on Wednesday, so I will have something by then.