BBS02 water damage?

[Anschutz]

Hello everyone, I have had a BBS02 750 watt drive on my bike for a little over a year. Code on the housing indicates it was manufactured in January 2015. It is the 25 amp version with 9 mosfets. Total mileage on the motor/controller was just over 2000 km.

A few days ago I washed the bike with a hose and water. I did my best to avoid directly spraying the motor and components. A day later I took the bike for a spin. Curiously the display gave an Err 12 code when pressing the pedal assist button on the throttle. (This was the first time I ever received an error code) Shutting off the battery and restarting would cause the error code to clear. After the ride, I put the bike in my garage however forgot to turn the battery off. The next day I was working in the garage and heard the motor making sizzling/crackling sound and saw a puff of white smoke, then no more sizzle. This is when I realized that I had not turned the battery off.

Today following instructions on this board and elsewhere, I disassembled the motor and dug the controller out of the housing. Pictures are of what I found. I think my only option is to buy a new controller, however would like to avoid a similar fate in the future. So what does everyone think? Was it likely water in the housing that caused the damage? Strangely I didn't find any water in the housing when I disassembled.

 

[alfantastic]

Could possibly be water damage that caused the demise of your controller. It would only take a drop on the wrong part of the board to fry it.

I think you've been unlucky, coz the controllers are potted and look fairly waterproof as standard. I would fit a new Bafang controller and maybe add some extra waterproofing with something like this stuff:

Never Wet Rust-Oleum 18 oz. NeverWet Multi-Purpose Spray Kit

 

[Anschutz]

Thanks for the reply and the water proofing tip. Are you suggesting spraying the outer housing with that stuff or the inside of the controller? I am thinking of adding a layer of silicone on top of the potting material on the controller, plugging all holes and sealing the housing with RV gasket sealant.

It does seem strange that the board fried on the underside. When I removed the potting, the top side of the board looked perfect and I was starting to regret having started. Rather than stop though I decided to go 'all in' and remove the heat sink and board. The board came out of the housing with the potting material still attached to the board. My heart sank when I saw the amount of damage after peeling off the material from the board. On a positive note, I think I was able to find the problem.

The more I think about this, the more I am starting to doubt the damage was from water. Considering how sealed the controller was, I think this may have been due to a chip on the board burning out. Perhaps because I forgot to turn the battery off the day before. I'd be interested in hearing from others about their experience leaving the battery on for extended periods of time when the bike is parked/sitting.

In any event I ordered a new replacement controller from EM3ev last night. Should arrive in about a week. Hopefully it will bring my bike back to life and last much longer.

 

[alfantastic]

I reckon that your blown controller was one with Bafang's rubbish MOSFETs. See link for details:

https://electricbike-blog.com/2015/...using-crappy-mosfets-in-the-bbs02-controller/

Mine was an older one and the controller just mysteriously blew one day. I didn't open it up to check the circuit board, but I bet it looked similar to yours.

I replaced it with a new one, like the one you have bought from Paul, and it's been running sweet for 1000's of miles.

 

[Anschutz]

Yeah, I think the fried board is the result of an inferior electrical component and not due to water. The blackened area of the board is on the underside of the controller and was completely sealed with the potting material. In the picture you can see how I was able to peel it off in one piece from the back of the circuit board. Strangely the mosfets (all 9 of them) looked good. Perhaps when a mosfet goes it causes other parts of the board to get fried? In many ways I hope it was due to a low quality mosfet. I'd feel much better knowing I won't encounter the same problem with the new controller. Worst part of this experience is that my bike is sitting in pieces and I only have a couple more months of riding!

 

[Anschutz]

BYTW thanks for including the link to the article. I had come across the article while researching what could have happened to my controller. It was because of what I read in the article that I decided to give it another go and buy a replacement controller from EM3ev.

 

[cell_man]

It is strange that you had this issue after washing the bike. Personally that doesn't look like water damage, but who knows, it can't be ruled out. I do know that Bafang thought water damage was enough of a problem, to re-design the case and add a seal (new version, which has been supplied for the last few months).

On your version of the BBS02, the controller has a drain hole, so there is no effort to seal the controller, more than the potting that is used on the controller electronics. I guess it was assumed that the potting was enough on it's own (and to be honest, you would think it would be enough), to avoid water damage. Bafang would not have gone to all that trouble and expense to re-design the case, get new casting made etc, if they didn't feel it was worth their while.

The 3077 version controllers were generally released in around August 2015 on the 750W BBS02. I can't see how adding some silicone on the joint between controller and the housing, and also sealing the drain hole would cause any issues, then you would have some additional weather protection, over and above the potting.

I'd also check the motor windings are in good shape too, when you have the motor apart. A blown controller can be a symptom of a burnt out motor.

 

[Anschutz]

Thanks for the reply. Your tip about checking the motor windings makes sense. I have the motor apart and wondering if there is anything I can do over and above a visual inspection of the windings. Perhaps check resistance of the coils? Any suggestions? I think I will seal the motor and drain holes with some sort of silicone when I put it back together. While I understand the rationale I think it makes more sense to try and prevent water from getting in the motor.

 

[cell_man]

With a hub motor, you can check a motor by rotating it with the phase wires disconnected, then linking different pairs and confirming that there is a strong resistance. With no phase wires linked there is little resistance, with any pair linked, it has a noticeable cogging, with all 3 linked, the feeling is a continuous constant resistance to rotation.

Unfortunately there are various 1 way bearings and stuff in the bbs motors, so I'm not to sure if this test can be done or not on them. You'd be turning the chainwheel to test the motor.

 

[sather]

???? Every BBS02 controller that I have ever seen have been encapsulated "potted" in a grey rubber like substance so none of the circuit board or components are exposed to moisture.

 

[cell_man]

???? Every BBS02 controller that I have ever seen have been encapsulated "potted" in a grey rubber like substance so none of the circuit board or components are exposed to moisture.

Yeah, and like I said above, I'm surprised that there are any issues with water damage on a fully encapsulated controller, BUT bafang probably know a bit about their motors and why they fail (and i heard as much from a senior person in Bafang). They must have thought it was worth their while to go to the trouble (and expense) of redesigning the BBBS02b to improve the water seal on the controller (in the same way the HD is sealed).

 

[Anschutz]

Well since my last post my new controller has arrived. I have not yet installed. Instead I'm taking some time to try and figure out what happened to the first controller. Here is a picture of the same controller with much of the black soot cleaned off (left). The image on the right is of the same controller taken from another post and placed side-by-side for comparison. From what I can tell, it looks like the solder bridges fried. Perhaps some moisture got between two bridges and caused a short?

I'm also going to check the motor windings with a ohm meter to confirm none are shorted. I'm having some difficulty however getting the windings out of the housing. Although I've removed the 5 hex screws, the windings won't budge. If anyone can point me to post or video on how to remove the windings and roller gear from the housing I'd appreciate it

 

[d8veh]

You can't short out a battery with water - not enough to heat up and melt solder anyway. It would vapourise as soon as it gets hot and break the connection.

At the position of your damage, you have a positive(?) track/trace adjacent to a phase wire connection but I don't believe that it was a direct short that caused the problem.

The mosfet must have opened or shorted, which would dump the whole battery through a single phase with the motor stalled, which would melt the tracks. It's vaguely possible that water caused a short between one of the mosfet gates and the battery positive, which would have switched on all three mosfets on that phase.

My guess is that one of your motor phase coils will be in a bad state, though it's possible that the track/trace blew before serious damage was done.

Only the tracks/traces between the mosfets and the battery are live. The rest of the controller gets its power through the LCD switch, which was presumably switched off.

 

[ziltoid81]

My BBS01 was literally under water some time when i rode through 30-40cm deep water, in addition to that i rode it often in heavy rain and never dryed the bike after, i doubt theres a moisture issue.
I commuted 12000km in every condition and its still running.

 

[Anschutz]

Well with weather starting to warm up, I'm finally back to trying to diagnose what went wrong with my BBS02 motor. I'm becoming more convinced the issue I experienced is related to water getting into the BBS02 rotor and coil. Here are a couple pictures. The first is of the coil. The second is of the rotor that shows rust. Seeing rust leads me to believe that water got into the motor at some point. I don't know however if water in the coil/rotor is what caused the motor to fail.

I have a new controller ready to install, however want to first test the continuity of the coils. Can anyone describe how to do this? I understand the BBS02 has three separate coils to test. I have a multi-meter however uncertain where to place the probes. I would really appreciate if someone could describe how to do this (or provide a picture/reference). Thanks in advance!

PS: Since my original post I have heard from others that have experienced the same issue. They disassembled their controller removing the potting material and the controller circuit board to be fried at the exact same location. It would seem this issue is not an isolated case and likely due to a design flaw with the BBS02.

 

[walls99]

Testing the continuity of the coils is not going to be that helpful because the 3 windings are connected together, so they should test as shorted between any of the 3 phases. See: https://en.wikipedia.org/wiki/Brushless_DC_electric_motor#Variations_in_construction.
It's unlikely the motor is going to be the issue unless it overheated and this would be easily visible because the winding would be dark/burned up. But if you really want to test the motor winding you need either a precision milliohmmeter or an impedance tester, see this thread for more info: https://endless-sphere.com/forums/viewtopic.php?f=2&t=21454

Looking at the pic of the damaged controller board, I've noticed the 5V regulator marked ST 78LM05 and its surrounding are looking darker than they should, it could just be residue from the main meltdown but if not, a failure of this 5V regulator could have caused the bigger meltdown...

 

[Anschutz]

Thank you for the reply and the links. From what I've read it sounds like the only way for me to test is to have an electric motor repair place check it out. Do you know what the implications would be of connecting a new controller to a motor with burnt windings? I suppose what I'm asking is if burned windings can fry the controller. I'm tempted to put it back together attach the new controller and see how it goes. It would be a shame however if by doing so it ruins a new controller.

 

[walls99]

Your motor windings look fine from the pic you posted, burned windings are easy to spot, see a "good" example here: https://endless-sphere.com/forums/viewtopic.php?f=28&t=58898&start=875#p1240836.