Motor Dies on bumps

[stmacdonell]

I have a Bafang BBS02 on my bike with a 20ah 48v battery that I bought and installed this past fall (2015). Things were going great until Monday when my wife hit a bump and the motor stopped responding to the throttle and peddle assist (display was still active and didn't show any errors or a low battery or anything). When I got home I played with the throttle a bit while I had the rear wheel lifted off the ground. The motor was cutting out at some pretty low speeds (that varied). Powering the unit on and off didn't seem to help. I disconnected the battery for a bit and that seemed to fix it.

I took it for a ride and it certainly wasn't cutting out, but it's noticeably less powerful than before. It's been a few days, and its cut out a few more times after hitting bumps, and disconnecting and reconnecting the battery seems to be the only solution.

Where should I look for a problem?

 

[Sunder]

Check the phase wire connections. You could be running on only two out of the three phases.

 

[dogman dan]

Sounds to me like the battery this time,, but usually it's some kind of connector problem.

 

[stmacdonell]

Check the phase wire connections. You could be running on only two out of the three phases.

What are the "phase wire connections?" I.e. what part of my set up do I need to look in?

Sounds to me like the battery this time,, but usually it's some kind of connector problem.

So, you don't think it's a connector problem? I've got a watt meter. Can I use that to tell if it is or is not a battery problem. i.e. if it's sending less than X watts, it's probably the battery... (I'm thinking of running the motor with the rear brake somewhat engaged).

Thanks for your thoughts both!

 

[keithmac]

Phase wires will be inside the motor end housing (iirc the lhs cover is the controller).

 

[docw009]

If you got a wattmeter between the battery and motor, is it the type that resets when the power is interrupted? Then you would know a little more.

I'd check the battery to make sure the cells inside aren't rattling around with broken wires. Seen that with a Dolphin battery when the foam rubber dried out, Had to repack it with styrofoam. Well, the wires weren't broken, but it yanked a connector off the LED meter.

 

[melodious]

+1 on connector problem.

Check the wheel magnet & magnet sensor.
Check connectors inside the battery holder.
Check the connectors between holder & motor.
May as well recheck the throttle pins & LCD pins.

Now for the harder checks they don't pan out... (Means opening up the motor to the internal controller)
Check the 3x phase wires inside your controller.
While you have the controller out, check the 5 pin connector.

Now for an even harder check if that still doesn't pan out... (Means opening up the battery housing to the battery & BMS)
Open the battery case, ID the BMS, check your voltages of each cell string, and report back here.

Charge your battery to full charge status, leave it there for 1/2 day to top balance. Put a meter inside the + & - sides and tell us the total voltage (13p or 14p )
My hunch is you have a battery that isn't fully connected to the controller/motor.

 

[keithmac]

There was a thread on here not long back where a connector under the controller cover wasn't fitted correctly (and then had silicone smeared on top of it) on a BBS-HD. If you pop the cover off make sure you have a good look at all the connections.

 

[brumbrum]

As mentioned by most, in my experience a motor cutting out on bumps means a loose wire/bad connection. It is probably a badly soldered wire that is coming loose. Start by checking all plastic connectors for any wires that may have worked loose or are fraying. Try removing plastic housing connectors and checking the metal terminals that are soldered onto the end of the wires. Sometimes it can just be that a metal terminal is not seated properly within the plastic housing.

 

[Jabotical]

How is the battery connected? Is it one of those that conveniently pop out of an attached rack of some kind, like a bottle battery/shark/dolphin/whatever?
If so, an easy first check is to verify that the battery connectors are making good contact. My holder/rack piece got a little loose and I saw some similar behavior due to it intermittently not making solid contact with the actual battery. To test I wedged the thing in really well with some pieces of cardboard, and the problem immediately went away.

 

[Sunder]

My guess and bear in mind its only a guess - even educated guess is too generous - is that there are multiple contributors to this problem.

My guess is that the root cause is running intermittently on two phases, causing a consistent loss of power.

But it is also causing the controller to run hotter. This is causing the other cutouts.

Removing the battery and putting it back in is allowing it to cool and forces the controller to take another thermal reading, allowing it to operate for a short time again.

I don't own a BBS02, so hopefully someone who does can give you some photos as to how to reach the phase connectors.

I'd also be careful riding it until you've got to the bottom on this. You could be degrading connectors and insulation if you're repeatedly hitting a thermal cutoff.

 

[stmacdonell]

How is the battery connected? Is it one of those that conveniently pop out of an attached rack of some kind, like a bottle battery/shark/dolphin/whatever?
If so, an easy first check is to verify that the battery connectors are making good contact. My holder/rack piece got a little loose and I saw some similar behavior due to it intermittently not making solid contact with the actual battery. To test I wedged the thing in really well with some pieces of cardboard, and the problem immediately went away.

I didn't get a chance to trouble shoot this today. Hopefully I will tomorrow after work. The battery is a 48v 20ah rectangle that looks more or less like this http://lunacycle.com/batteries/packs/48v/48v-panasonic-ga-18650-10ah-pack-performance-lightweight/ (has the connectors pictured). I ordered from Lunacycle and my order says "48v Samsung 18650 20ah ebike battery"

Basically, I taped a bunch of foam to the frame where I wanted to mount the battery so it wouldn't slam into the frame, and then used A LOT of paracord to tie it in place. The XT90 connector from the battery connects to the one going into the BBS02.

Also, just now I tried running the throttle with the wheel off the ground and the rear breaks engaged while the watt meter was hooked up. I read 1300+ watts a few times and it didn't seem to cut out (unless it sensed it was hitting the speed limit I set.)

 

[Jabotical]

Yeah if you've got it connected directly with an XT90 connector like that (not going through a cradle like I was wondering) then the issue is almost certainly not your battery making intermittent contact. Probably should look to the earlier posts for guidance and ignore mine

 

[stmacdonell]

So, sorry i'm slow. I didn't have a lot of time to work on this. I opened it up and was only able to get the left side off. It didn't look like anything was loose. I put it back together, and now when I try and start it up I get Err 8, which it says has something to do with the "Hall sensor." Do I need to get the other side off?

 

[d8veh]

If there were any problem with the battery or its connection, the LCD would go off, and then when you switched on again the LCD, everything would be working again. OP said the LCD stayed on. That means that the problem is between the motor and the controller.

The motor connections are pretty poor. One of my ones wouldn't even stay together, so I had to use pliers on it to get it to grip. Also, the hall connector can give problems, but in that case you normally would get an error code in the display.

It's easy to service the motor connectors. remove the chainwheel to get access to the controller compartment, and then remove the controller, which is moulded into the cover. It leaves it dangling on the motor wires.