Weird failure, any ideas?

[KirstinS]

So my commuter with a front BPM hub, 48v controller and battery just cut out on way home Wednesday

Small bump /pothole and stop

But, and this is the odd bit for me, I have power to LED panel and the throttle provides momentary and weak power before cut out.....then nothing

I've checked the battery (fine on my other bikes and reads ok on the meter too)

I've checked the connections. It's a square wave , throttle only, led setup - so simple as they come

Tested all connections, very flummoxed

Controller dead? Seems unlikely to me as no growly, busted fet sounds

Any guesses ?

Or is there , somwhere. A dodgy connection that I have yet to find?

Thanks all

 

[Deleted member 4366]

It can be loads of things. Measure the 5v to see if there's a short or your 5v regulator has popped. If that's OK. check the phase connectors aren't melted, then open up the controller to check that tracks haven't melted.

 

[Woosh]

I could be one or more FETs.

 

[danielrlee]

This sounds like a problem I had a couple of years back with a sensorless controller. All tests proved inconclusive until I tested the controller with a brushless motor tester which revealed a screwed up phase timing. I never discovered the cause, but replacing the controller solved the issue.

My first suspicion though is that you have a dodgy phase connection as d8veh mentioned.

Also, have you tried another known good throttle yet?

 

[KirstinS]

Ok, I finally gave up and ordered a new controller

Solved ...or so I thought.

Turns out my main Jimmy at insat battery is on the blink. I reckon there must be a loose connection somwhere . It's reading low at output (around 35v) but won't charge

Given the sudden failure over a bump im hopeful for a duff connection over a duff cell/string

Will take it apart tomorrow and have a look see

Gutted though , it's only 16 months old

 

[Woosh]

I reckon there must be a loose connection somwhere . It's reading low at output (around 35v) but won't charge

bumps can kill the BMS.
Open the battery and check the voltage at the balance leads.

 

[KirstinS]

bumps can kill the BMS.
Open the battery and check the voltage at the balance leads.

Thanks, I've set this evening aside to diagnose /dismantle

I do have a spare bms for this case

 

[KirstinS]

Update , after Woosh post i feared theb worst

But then I recalled the intermittent nature of fault

Opened up battery... Two bad welds with flappy nickel strip, see photo

I've lifted for photo but must have been connecting /disconnecting to give intermittent fault

 

[KirstinS]

 

[KirstinS]

 

[KirstinS]

So, that was the issue

Dodgy/broken weld on cell pack due to bump

So convinced was I that issue was controller I bought one I don't want ! And an LED

Grrr

But, very grateful a new battery isn't required , everyone needs a spare controller (although I have at least 4 now - but only one 48v)

 

[KirstinS]

And, for completeness I did test another throttle beforehand and check phases (though not inside controller on.pcb tracks)

I now solder all connections direct including phases since I've had previous issues there

And the thread ends on a happy note

Thanks, as ever , for time and input folks