Unique brushless hub motor issue.

[Mrman7627]

Hello, this is my first post in this forum but this forum has been an asset to me for various ebike issues so first and foremost I'd like to thank all the experienced people here for help with problems I've had in the past. I'm fairly familiar with various aspects of brushless hub motors due too my own trial and error I've replaced a bms before and done other maintenance to other batteries but haven't done a lot of work to the motors themselves though I do feel confident in my abilities to repair an issue when I can determine a problem area and have tried searching for this issue too no avail



I have a 48v 1000w brushless hub motor on the rear wheel for my ebike and a 48v 20ah battery. "Both were the cheapest china made types i could find" I use this ebike for my daily commute too work. About 14 miles per trip twice a day. It's been a trooper and has worked great. Ive ridden it in the rain a few times without issue sense ive tried to do everything i could to weather proof it "just mentioning this too give the most info i can". The issue I'm having is this. I was on my way to work and the wheel partially locked up after almost a mile of riding I could spin the wheel but it was EXTREMELY difficult if I tried to spin the wheel by hand as soon as my hand left the wheel it stopped spinning. I thought it felt a little wobbly when I was riding it this morning but I just switched tired and tubes too a thinner width and it was really windy so I don't know if it was the wind and tires that made it seem weird. Regardless of if the battery was connected or not it was still very hard too turn it.From what I studied the main possible culprits were something being lodged between magnets or the bearings seizing. After taking apart the motor I found the bearings were great and there was nothing lodged between anything. But the magnets on the motor and the wheel itself seem to be sticking to one another not with anything other than there own magnetism nothing has come unglued and the hall sensors appear to be there and in working order however 3 of the little magnet sections on the outer rim of the ebike have a extremely small section of rust. The magnets are also just a tiny bit greasy. In the past I noticed a bit more resistance when riding the bike with no power I sprayed a little wd40 on where the bolts go on and I thought this solved the problem thought i hadnt felt this issue in weeks . But as I said today it messed up. The magnets on the outer rim seem to be sticking magnetically to the magnets on the motor itself when I went to put the motor back together when I was sliding the outer magnets/tire back together with the motor itself they REALLY slammed back together and when I go to try to spin the wheel I still had that extreme resistance and there is no battery connected to it. Also the spinning even with the resistance is clicky? Like it isnt a smooth moving it moves in little ticks. No audibke noise just tick tick tick is what it feels like "I know not a great description but its the best way i can put it into words". The ONLY thing I can think is that some of the wd40 got into the inside of the motor which caused the slight greasy Ness of the magnets and that's somehow causing the magnets to magnetize to each other moreso than usual. My next plan is to use a LITTLE bit of soap and water to remove the greasy Ness and ensure everything is bone dry and put everything back together. I'm at a complete loss it seems so strange any help anyone could give me would be greatly appreciated.

 

[Hwy89]

My thought is that one or more of the magnets have come unglued. When you pulled the stator out they pulled back into their slots. If you take the motor apart again try using a narrow flat steel bar against each magnet and see if any of them can be lifted out.

 

[dogman dan]

No, you have a blown controller. The little ticks are each magnet going by, with a short in the system.

the cogging will go away when you unplug the motor wires. If it does not go away, then your motor has a short in it, and is toast. But usually, the short is caused by a blown fet in the controller, so when you unplug, it disconnects the short in the controller from the phase wires, and the cogging goes away.

It could be the magnets you can easily have both problems at once, but the more likely possibility is its in the controller, or you have a shorted phase wire in the motor.

One possibility for a motor short, is the wires got melty or damaged at the axle, so don't write off the motor immediately if unplugging the controller does not free it up. Usually if the short in a motor is in the windings, its fairly obvious, all black and stinky in side, when the varnish cooked off the winding wire.

 

[Mrman7627]

Alright thank you both for the advice! It's crazy how the controller can still affect the motor even when there's no power going too it. Ya learn something new everyday! One other part I forgot to mention when I was walking it home if I lifted the back wheel up and tried to move the throttle the tire would try too move but just stop when I think about it sometimes on my initial start of my ride as I'm peddling to help get it up too speed I would hit the throttle and it would start then stop then id try again and it would be fine so i writ it off to my tire being a little too flat and assumed it was just trying to give too much power so the controller does sound likely. The inside of the motor didn't smell and I didn't see anything that looked scorched but there were times where after my ride the motor felt hot not warm but hot. Though that was intermittent. And that sometimes working and sometimes not working sounds like the controller too! Luckily I have another controller and motor but the wheel the motor its on is warped so ive gotta transfer it to the other wheel from an accident though and the controller didn't come with any wire harnesses on it so to ensure I wire everything correctly too the throttle I've gotta make sure I wire the two red wires it has on it correctly so I don't destroy "another" throttle. Well I should be able too fix this when I get home from work today. Thanks again everyone I'll give an update after I finish the work!

 

[Alan B]

When the motor turns it generates voltage. If there is a short anywhere in the motor or controller this generates current that opposes the motor's rotation, you have a shorted generator. Just like having maximal regen. So you do have power, just not from the battery.

 

[Hwy89]

I assumed that the motor wires were unplugged from the controller when you disassembled it.

 

[Mrman7627]

It WAS the controller!!!!!! I feel silly for not unhooking the controller and testing things. Just got back a bit ago from a 14 mile ride and everything is in working order no overly hot motor no random stopping when i hit the throttle and in fact my battery seems to be running more efficiently now as in its not draining quite as fast "though the tires being a smaller width might have something too do with that as well or perhaps its because i re-secured all the connections and maybe they are working better i dont know". Whats weird is i dont see any visible damage to the controller all the capacitors and resistors are on the board none of the capacitors are bloated no scorching and all the different chips and what not still seem too be present. I would like too figure out what went wrong and why the problem was intermittent instead of instantaneous. Im gonna look around on some other pages here and see what the best way to prevent something like this from happening in the future. I may have caused the controller to overheat now that i think about it "i covered it and some of the areas where there were connectors in a little duct tape as a temporary water proofing solution until i could either get a good frame or find a better solution not a ton of duct tape mind you but i suppose anything that inhibits a cheaply made china controller from dissipating heat may cause an issue. Once again thank you all for your advice and patience! Ive been reading through some other threads on here "i find the one about building batteries and the issues a person was having with multiple faulty BMS boards of particular interest cause i was planning on experimenting with that myself and felt it had some GREAT insight. I also noticed how PATIENT and nice people in this forum seem too be. Often times in other forums i see people getting flamed all the time "especially if a person doesnt listen to whats being told too them until they are told multiple times lol" But on here i see nothing of the sort so far and that makes me pretty happy. I hope in time as i gain knowledge i can become an asset too this forum as well. Have a great night everyone!!!

 

[dogman dan]

If your short was a blown fet, it could not fix itself and then run again. you have a short somewhere else, likely in the wiring to the motor. This is a short on the fat wires, if it was cogging like hell..

if it was cogging. if it was stuttering, that's just more likely a bad connection on any of the motor wires, but more likely to be the small halls wires or that plug.

Intermittent problems are wiring issues, 99.99999999% of the time.

To see what cogging really is, unplug the motor, and somehow connect and short two of the big fat wires, then spin the wheel by hand.

I'm thinking you have stutter now.

 

[Mrman7627]

Well when it happened a little bit before I could still ride it there was just some excessive pull and a light cogging similar to the recent problem just not nearely fully locked . I have ridden it before with one of the big wires not connected and it wouldn't really start until I had peddled for a few seconds with no power then would just feel like it was randomly cutting out for a few seconds. As of today I've taken it on two 14 mile rides and it's running great though the rear wheel feels a TINY bit wobbly until it's up too speed but I also just noticed I put the tire tread on backwards or thought perhaps I didn't do a good enough job seating the tire as I was on a time limit so I thought either of those two things could've caused it. But other than that great. I rescued all the wires this time a little differently cause there was no throttle wiring harness so I had to splice the wires together and the three big wires are better secured this time as well. The three hall sensors looked intact though one looked a little but more rough on the part that's embedded into one of the magnets but it didn't really seem bad just a tiny bit degraded in comparison too the others. The connectionsecond could have been a bit bad as I had covered them in duct tape to do a short term water proofing attempt. One of the three resistors on the old controller was a bit higher up than the other two but it was still properly soldered.