Sabvoton 72150 ukc1 usb phone charger shorted!?

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Sep 29, 2015
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Location
london, uk
Hey everyone.

A very strange one last night. I had my usb phone charger lead charging my phone plugged into my ukc1 screen. o
n the right hand side there's a USB with a rubber cover.

You have to hold down the m button to send power to charge a phone. Or whatever.

I pull my phone out, the charger lead which plugs into the phone usb-c touches the suspension fork. A massive spark happens, then display goes. I got it back on after unplugging and plugging the battery. Then error 30h, twist throttle display goes again.

Tried usb Bluetooth on sabvoton to check for issues but the usb doesn't work.

I'm thinking this has blown the 5v rail.

Anyone shed any light ? Before I start opening up controller. And shouldn't this be fused ??
 

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That kind of damage and "massive spark" is not a 5v thing--that's a battery-voltage thing.

Most likely there is a wiring fault somewhere (possibly even internal to the battery and/or controller or motor) that is allowing the battery positive to connect to your frame, thru any point in the wiring that has battery positive voltage on it.

Then when the metal "shield" of the USB connector touched the frame, it provided a ground path for the battery voltage, with the results you see. (presuming the other end of this cable was plugged into the bike's USB port)

It is possible that during the arc flash that the current thru the ground wire in the display cable exceeded what the connector pins, crimps, thin wires, etc in the display itself or in the display-to-controller wiring can handle, and damaged it enough to not work normally, but still allow enough of a connection to sort of start to work.

It is also possible that the current flowing thru the ground in a spike like that generated voltages inside the display or controller that exceeded what some part or parts could handle, and they were damaged in a partly-functional way.

The wiring you can check out visually and with a meter, or just replace it.

The electronics are not likely to show a visual failure, and wihtout knowing what the measurements were before the failure, you may not be able to detect which part failed in the typical multimeter tests. It might require swapping out the display and wiring harness to test if that's where the problem is, or in the controller.


Regarding fusing, since this happened thru the ground path, and the fuse on the battery positive is meant for a much higher current, I don't know of a typical design that would have helped. It would have required a really fast blow fuse in the ground or shield of the USB port itself. It does sound like the battery's BMS shut off like it should have, just not fast enough to prevent damage.

But I don't expect they fused anything on the USB port, anyway, as I see direct connections to those things in all sorts of devices these days. Some have electronic switches on the 5v power to the USB port, but not fuses, and nothing on the data or ground lines.

I don't know what the standard is, if there is one.
 
amberwolf said:
Most likely there is a wiring fault somewhere (possibly even internal to the battery and/or controller or motor) that is allowing the battery positive to connect to your frame, thru any point in the wiring that has battery positive voltage on it.

I suppose the most likely place to start looking for the culprit would be the wire routing from the battery to motor?
 
The first test I would do is to turn on the battery if it has a switch, set your voltmeter to 200VDC, and measure voltage between battery positive and the part of the frame where the spark occured. If you read any steady dc voltage at all, it means there is a connection to the frame somewhere that shouldn't be there.

If you read a steady 0VDC, then measure voltage between that spot on the frame and the battery negative. Again, any steady voltage reading means connection.

Flickering changing voltages usually just indicate stray RF, but you won't typically see this on the 200VDC setting (but if you have autoranging on then it may read stuff at the low scales that isn't from the ebike stuff).


If the battery has a physical switch on it, or is in a cradle and can be pulled out, turn it off or remove it. Then set the meter to 200kohms or auto ohms, and measure between that spot on the frame and the wiring or cradle's battery positive connector pin. Any reading lower than "OL" means there is some form of connection between them, and there shouldn't be.

Same thing for battery negative, if you get OL on the first one.

(If your meter doesn't show OL on the screen when the probes aren't touching anything in ohms setting, then look for whatever it does show then).



If you get any reading in volts or ohms showing a connection, you can first disconnect the battery to controller connection, and see if it's still there. If it is, then it is in whatever wiring or mounting remains connected to the battery or cradle. If it does not, then it is somewhere in the rest of the system.

If the latter, reconnect battery-controller, and move to the next connection, disconnecting and rechecking, etc. This will narrow down to a specific spot or at least section of wiring pretty quickly.



If you don't get any reading showing a connection, you can look for damage or unintended connections anyway.

It could happen anywhere wiring or electronics casings can come in contact with the bike frame. Specifically, anywhere the battery positive wiring could come in contact with the frame or a piece of metal connected to the frame.

For instance, if the controller casing is metal, and internally it is shorted to battery positive (it should be isolated, not electrically active at all), and the casing is clamped or bolted to the frame, that would do it.

Same for battery casing.

For wiring, the most likely fault (for hubmotors) is where motor wiring comes out of the axle, if the axle edges have damaged the outer jacket and then the phase wire insulation. Then, *if* the controller has left battery voltage on a phase for any reason (which shouldn't happen when you're stopped, but...) and that happens to be the one with damaged insulation....

(if multiple phase wires were damaged and touching axle metal, the controller would probably have failed due to shorting between FET bridges)
 
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