Bafang BBSxx - fault finding and fixes

Done some measuring and got some weird results. High side driving seems okay, but all three low side gate signals looks weird. Will try to replace the driver.

Can somebody explain how this 9 fet configuration works? Seems like low side switch have 2 fets in parallel.

P. S signals measured relative to battery negative.
 

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The low side drive does not look healthy.

Justas said:
Can somebody explain how this 9 fet configuration works? Seems like low side switch have 2 fets in parallel.

Yes, two in parallel on the low side but only one on the high side. In designs that are not using synchronous rectification, the low side FETs have to throw off more heat when they are acting like freewheel diodes.

The BBSHD controller apparently uses synchronous rectification. I have never tested the BBS02, but your waveform indicates synchronous rectification. Otherwise, the low side would only be switching for commutation and not at the PWM frequency.

So go figure why they used 9. Better than 6 but didn't have room for 12?
 
Searched full thread but could not find a good pic of the back side of a bbs02b controller. I have a 36V500W with some burned parts, resistor suppose, if someone can check with a miltimeter to give me the data of the burned two and maybe the two nearby...
The place where resistor are attached to board are partially damaged, so if someone can also draw a line on how to connect them to the next contact, it would be perfect.

Strangely enough this controller, coming from a 36v500w bbs02b motor, had a 48V500W label under the rubber. But this is another story...
https://drive.google.com/file/d/1XWa2PuB7b94tnHPKfmt5KToVtqScKkEX/view?usp=drivesdk
 
banzai said:
Searched full thread but could not find a good pic of the back side of a bbs02b controller. I have a 36V500W with some burned parts, resistor suppose, if someone can check with a miltimeter to give me the data of the burned two and maybe the two nearby...
The place where resistor are attached to board are partially damaged, so if someone can also draw a line on how to connect them to the next contact, it would be perfect.

Strangely enough this controller, coming from a 36v500w bbs02b motor, had a 48V500W label under the rubber. But this is another story...
https://drive.google.com/file/d/1XWa2PuB7b94tnHPKfmt5KToVtqScKkEX/view?usp=drivesdk

These are ferrite beads for suppressing noise in signal lines. You could try to short them if don't have any at hand. This is my controller photo:
https://photos.app.goo.gl/5hpm49AGH5Tb2sRH6
 
The way those are burnt is not a good sign. Something likely shorted to blow those out. If you are lucky, it didn't take out more parts.

I have a BBS02 board around somewhere but at another location. I'll see if I can find it and trace out what those go to.
 
Thanks Justas and fechter, now board at home and I'm out, yes agree with you, I found the main cable just near connector compressed, need to verify if some of the cables are shorted. I tested the Fets from the three cables (YGB) and they seem disconnected, but if I test to the fet legs, and have similar results so they should be OK.
 
The way I test N-CH FETs:
0) Disconnect any other source of power.
1) Disconnect any load that mimics a short (motor windings)
2) Using two volt/ohmeters to measure each other. Set one Ohms the other Volts.
3) Each need to output more than 4V on ohms test to have any chance of working.
4) Abuse one ohmmeter across +drain to -source to power and measure the channel.
5) Abuse another ohmmeter to bias +gate to -source.
6) Observe the channel begins to conduct, or at least it should.
7) Reverse bias -gate to +source, but leave +drain to -source ohmmeter as-is.
8) Observe the channel begins to insulate, or at least it should.

Forward biased gate to source probably shouldn't conduct, but depends on circuit.
If less than 500 ohms and not driven by a pulse transformer, I'd be suspicious...
An ohmmeter won't be able to bias that sort of circuit.
 
Traced the spot, goes to Brown cable, P+ from display cable. Anyone can give a clue on ferrite beads values? Managed to found four of them near mouse/keyboard ps2 connectors from an old mainboard, could be ok? Stupid question maybe...
 
I don't think it's critical. Pretty much anything that fits should work.
The brown wire feeds full pack voltage to the display, so if the wires shorted, there would be enough to blow it.
 
Im making a poor man BBSHD, I plan on bolting a bbshd core to my BBS02B case and see if that woks. Im just wondering if the rotor shaft of the BBSHD is longer or shorter than the BBS02B, I know the rotor itself is longer but dont know if the coiled shaft is. I know the bearings are the same. Cant do this for another month so we'll see.
 
Nope. Two very different builds.
 
Hi

I have a problem.

The gear on my Rotor with Bearing (BBS-HD) has been cut off.

How is that possible?

And how do I replace it?
How do I remove the Rotor. The Gear is gone and the Rotor is stuck as a rock.
Where do I buy it from? Most cheapest? And fastest delivery?

BR.

Jens...
 

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It should be noted that in april 2019, Bafang changed their rotor design on the BBSHD and use a larger bearing on the motor stator lamination side. Because of this, if you break your rotor from one manufactured before this date, you will need to order a complete stator+rotor setup. Here is a picture of the differences, the greased one is the original one:
20190624_234253.jpg
 
Nope, I think we have a fix from California eBike. Doug ships rotor with backwards compatible parts.
 

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Just remember that not all vendors who supply the parts will set it up for being backwards compatible. Im still waiting to hear back if the bearing is a 606 as they said or a 609, as the dimensions they gave are for a 609. Oh and that is me who asked on FB lol
 
Can anyone tell me if the Nylon gear should spin when pedalling? Have quite a bit of resistance when pedalling and wonder if this is the problem?

*edit* If i remove the nylon gear/pinion, there's no resistance when i turn cranks, resistance must be from either the bearing/freewheel inside the gear or the bearing between them?

I expect "some" resistance, but on a flat it's quite difficult to maintain 10mph/16kmh when battery is off.
 
There's a freewheel between the cranks and the gears. Possibly yours got stuck. There should be essentially no resistance to pedaling from the motor.
 
The freewheel in the nylon gear seems to operate normally, only turns one direction.

Only option is to buy new one and see if that works with less resistance?
 
One more thought....
It's possible the grease on that freewheel has gotten sticky with age. It might be worth pulling the gear off and clean the shaft and the inside of the bearing as much as possible, then use some new grease. There may be a better grease than the stock nasty stuff. If the grease got gooey, you'd be pedaling against the goo.
 
I have a early BBS02 with another blown controller. It lost a leg on a steep climb while on a low (30 -40% current) pas setting but was steep enough to slow the cadence significantly even with significant rider input. Total weight was under 170 pounds but enough. Unfortunately, finding they changed the case when going to the 3077 FET. Does anyone know how to tell for certain that the old style case controllers sold today are made with the 3077 and who may have one. Options for more robust aftermarket controller? Unit has very low miles. Anyone interested in it at a reasonable offer, PM me.
 
Good old Bafang doesn't share any serial numbers tied to changes.
I'm curious, how fast were you riding and climbing and what was your gear ratio?

Controllers are getting really hard to find for "A" version BBS02. Often expensive enough to justify a bare motor BBS02B.
 
It has a 46 tooth chain ring on it and a 32 rear. May need to go up to a 42 or bigger rear to have avoided the controller overheat. My 110 pound grand son was on it pedaling some 50 -55 rpms next to me when it went dead. Just on low pas level settings, maybe 40% power. Center leg again. We were about a mile up the hill that is steep, between 15 - 20%. We were over the worst of it but fortunately we did not get over the ridge and deeper into the woods or it would have been a chore getting back. Pack is 12s lipo. Looking to possibly swap it all out for a bbs hd. I think I can swap a bare bones hd with the existing display and cables. Would still be good for a commuter build but I don't usually keep anything around that fails repeatedly as this has. Cali edikes and luna both have the 25A A version.
 
speedmd said:
It has a 46 tooth chain ring on it and a 32 rear. May need to go up to a 42 or bigger rear to have avoided the controller overheat. My 110 pound grand son was on it pedaling some 50 -55 rpms next to me when it went dead. Just on low pas level settings, maybe 40% power. Center leg again. We were about a mile up the hill that is steep, between 15 - 20%. We were over the worst of it but fortunately we did not get over the ridge and deeper into the woods or it would have been a chore getting back. Pack is 12s lipo. Looking to possibly swap it all out for a bbs hd. I think I can swap a bare bones hd with the existing display and cables. Would still be good for a commuter build but I don't usually keep anything around that fails repeatedly as this has. Cali edikes and luna both have the 25A A version.

Easy peasy change out with a bare motor. BBS02 motors need to be ridden as if they were acoustic bikes and the motor is there to assist. Lugging kills them! Get lazy and ride in a gear you wouldn't pedal in with assist...see ya!
 
Agree Tom. They should have added thermal roll back on this setup. Interesting to see the phase runner and ca setups on the HD. That would be a big improvement to the stock setup. Not sure the BBS02 is worth trying to retro fit with all it's mechanical shortcomings. New style stock controller and at least a temperature probe-indicator should keep it working if I decide to keep it a bit longer.
 
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