motor cutting out question

[sal_park]

Hi Guys,

I had a bit of an adventure 2 days ago on the way to work - tried a new route and what appeared to be a big puddled turned out to be a flooded path - the water went about 1 1/2 foot deep so the front hub motor (250W bang-fang) was well and truly submerged. I used the motor all the way through the ~600 yard section and it was probably submerged/running for 1 1/2 minutes or so. Everything was fine on the rest of the journey, and again on the way home, although the motor was a little noisier than normal.

Next day on the way home from work (the bike had done around 7 miles since going through the flood) the motor cut out a few times It seemed to be if I'd not used the throttle for a short period that it would happen and would never cut out while I was using the throttle. It only did it a few times and at the end of the ride I could not provoke it into breaking.

I suspect it's the throttle control (thumb type) as the mechanical action of this was getting a bit stiff so I sprayed it with WD-40 a few weeks ago.

Also worthy of note - the controller and battery did not go underwater and I think the battery is fine as my lights (powered by the battery) were working fine while the motor was not.

Anyway, what do you think ? All comments welcome.


sal_park

 

[dogman dan]

Most likely culprit would be the plug connections on a 5v circuit. So either a throttle wire, or a halls wire to the motor got damp and lost contact intermittently. Can happen with wet, even when the plugs look good. On the other hand, I've ridden around puddle splashing for miles, soaking everything and still had it run fine.

Generally even quite a bit of water actually inside the hub cannot cause a failure, since everything inside is soldered connections. But it might be worthwhile to investigate whether the motor really did drink in some water, since you don't want corrosion inside on steel parts.

 

[sal_park]

Thanks, I'll take a look at that. The obvious thing (now you've said it) is the motor has a 3 pin plug which was fully submerged.


sp

 

[dnmun]

the motor also has hall sensors which were shorted out when they got wet.

 

[d8veh]

A couple of things that I can think of assuming a sensored motor (3 big wires plus 5 small ones):
The motor halls got soaked and stopped working. You have a controller with automatic hall detection that can work sensored and sensorless, so it switched to sensorless mode, which would account for the increased noise and slightly rougher operation. Maybe you now have intermittent contact on a hall, so the controller keeps stopping while it makes up its mind what you have.

The most likely problem will come from any mult-pin connector between the motor and controller, so if you have one, open it up and dry it out.

Worst case: you have water in the motor. You need to get it out before it does serious damage. If you have a motor where the side-plate/s is/are held on with small screws, it's easy to open up the motor. If you have a Bafang with a screw-on side-plate, it's nearly impossible to open the motor without the special tool, but you can drain any water by removing the disk screws. Then I'd squirt copious amounts of WD40 in to rinse it out and then keep it warm long enough to vapourise any remaining water before giving it a dose of oil of some sort (ATF).
This is what happens if you let water get in your motor, so whatever solves your problem, you need to check that you don't have any water inside:
http://www.pedelecs.co.uk/forum/electric-bicycles/10532-dirty-rusty-bafang-hub.html

 

[dogman dan]

Bet it was the wet phase wires plug if it was underwater. If some resistance occured on one wire, the motor would stutter every 3rd magnet, but still run. same thing happens under load if you cut all but one strand of a phase wire. The motor runs like, strong strong weak, strong strong weak.

Chances are, all is well now. But you might look inside the motor eventually to be sure it didn't suck in any water while running underwater. In general though, the motor sucks in moisture when it cools, not when it runs warm.