XB-508 Electrical Issue

[woodyvt]

Hi Folks,

I have a problem that I hope your expertise will help me solve...

First, I have an X-treme XB-508. I've never had a problem with it, reliable as all get-out.

I had my back-up battery pack in it yesterday (I have two for those days when I run a lot of errands). To make it easier to swap out batt-packs, I connected the terminals with simple slide-on connectors. While I was riding yesterday, the vibration caused one of the connectors to slide off one of the batteries and I lost power. This has happened a couple times in the past but I had just reconnected the one terminal and away I went. Yesterday was not the same... I connected the terminal, all was fine... I start up and less than 5 seconds later it just died. Crap!
I decide to push it the 4 blocks to my house. Here is the weird thing... As I pushed the bike there was this weird heavy pulsing resistance as the rear wheel rotated. What the heck? I disconnected the battery pack at the plug in the battery box and I put it up on the center stand to take a look... no resistance turning the wheel backwards but that same hard pulse type resistance rotating forward.
I had no other way to get it home so I pushed it the four blocks to my house. It was pretty hard because of that resistance in the rear wheel. I did try to pedal it but the resistance made that impossible.

When I got home, I checked the in-line 30 amp blade fuse and sure enough it is fried. I replaced the fuse, connect the battery pack, turn key on... Zap! Thunk in hub-motor! Fuse fried. Rear wheel started to turn for less than a second and there was a thunk sound from the rear wheel at the same moment. It was so hot in the fuse holder that it melted part of the metal connectors inside. Hmmmm? Out of curiosity, I rotate the rear wheel and now there is no resistance either rotating forward or backward. I tried hooking it up again and got the thunk/ burnt fuse again. Wheel also developed that strange pulsing resistance when I rotated it again manually.
I am pretty lame when it comes to complicated electronics. I can wire a house, I can tune a '60 Chevy but stuff like this and electronic theory boggles my mind.

So this is where I am at:
I disassembled the rear wheel/hub-motor and found that the center part(hub ?) was magnetized to the surrounding metal plates on the rim part. It took some doing and a fair amount of force but I got the center part out. I examined it but couldn't see anything burnt or discolored. I had it apart for about a day and when I reassembled it, there was no further magnetic effect and the wheel spun freely on it's axle. I put the wheel back in the bike, connected all wires except the three heavy motor wires, all 12 volt circuits work, I disconnect the batteries, connect the motor wires, reconnect the batteries, ZAP!, it actually burnt the heavy gauge metal prongs inside the battery pack-to-bike plug.

I have replaced the 30 amp inline fuse holder, the batter pack-to-bike connectors.
With all wires connected it constantly burns the 30 amp fuse.
With heavy gauge hub-motor power wires disconnected from the controller I can turn the key on and have power to all lights, horn, etc. and the fuse does not burn up. As soon as I connect the hub-motor I get a burned fuse, the hub-motor will sometimes "thunk" inside and now has that strange pulsing resistance when rotated manually.
It appears that the controller is working correctly and there is something very wrong inside the rear wheel hub-motor.

I have ordered a new controller and am waiting for that.

Whatcha think? Any ideas? If it's not the controller, what else do you think it could be?

Thank you in advance.

 

[Ricky_nz]

Fuses don't blow violently for no reason so don't keep replacing it!
Each time you are potentially doing more damage.
You should only replace a fuse when you have located the fault, not as a fault finding technique.

For a fuse to blow violently there must be a hard short somewhere.
Likely in the controller unless you can see damaged wires

If you don't have a multimeter it would be good to get one.
It will allow you to do some basic measurements to diagnose problems like this.

A meter would also help to be certain that everything is ok before replacing the controller
If you don't know what to measure there are plenty of people on the forum that can walk you through it.

 

[dogman dan]

The pulsing resisitance is often caused by a short at the phase wires. Cold be in the hub, or even in the controller.

Sounds like you may have cooked off your first motor. For starters, unplug everything from the motor to the controller, and see if the pulsing goes away. If it does, then your problem is in the controller, and much easier to replace.

 

[dnmun]

sounds like the mosfets in the controller are shorted. too bad you took the hubmotor apart. you can test the mosfets and if the phases wires are shorted with a voltmeter. much quicker and easier.

 

[woodyvt]

Thank you all for your responses.

Ricky_nz,

I was attempting to diagnose the problem by process of elimination... a fairly easy process with internal combustion where I have plenty of experience. I have zero experience diagnosing electrical problems and frankly, I don't want any. I'm the kind of guy who wants to be able to physically see what is wrong/broken and get in there and fix it. I can't see electricity. Mosfets, resistors, capacitors, blah, blah, blah, are beyond my feeble comprehension.

I personally hate this bike. The only reason I even ride this lame slow-poke thing is that they have changed the law in my locale, labeled gas motor assisted bicycles as "motor vehicles" and now require a driver license to operate a "motor driven cycle". I was just about to sell the sheepish thing when this problem occurred. Unfortunately I now have top spend money to fix it before I can get rid of it.

Anyway... that is a rant for another forum.

The motor has been reassembled and reinstalled in the bike. The power has been disconnected for well over 48 hours. The pulsing resistance to rotation of the rear wheel continues to exist in both directions.
Two questions regarding the hub-motor itself:
1) What could possibly be wrong with it?
2) Could I have whatever might be wrong with it repaired locally? I know of someone local who rebuilds all manner of electric motors for companies all over the country, some of them quite unique and very large.

Regarding the controller; I have ordered an OEM replacement... well, reordered... first place was back ordered so I have ordered from a second source.

 

[dnmun]

do you know how to use a voltmeter? can you go buy one at harbor freight? do you have a soldering iron and solder?