Wiring issues

[Herby]

Hi all. I’m encountering issues with lcd control panel messages and think there is a short somewhere in the wiring. I have replaced lcd and controller. Battery is good. The problem I think is the harness from the lcd (5 pin connector ) that joins the brakes (2 pin connectors) and then travels through the frame where it end in a flat 5 pin connector that plugs into the controller unit.at the flat pin end there seems to be no resistance between the red and blue wires. Obviously the same lack of resistance at the green 5 pin plug end. Ohm meter tested and there is continuity. I would have thought each wire would be independent and not connected in any way to any other wire.
Any suggestions on where to obtain a replacement cable would be appreciated.
Thanks

 

[matthewslack]

Try Ebay or a general online search.

But given that you will have to remove the existing cable from the frame, and fit the new one through it, why not remove, inspect and attempt to fix the existing one?

 

[Herby]

Thanks Matthew
I’m thinking the short must be inside the sealed connector as the cable seems to be unbroken.

 

[Nealh]

If the trunk cable runs thru the frame and and then has a sharp bend i it as it leaves the bottom of the frame to the controller then often this is wher one will like have an issue. Although visually there seems no break in the outer sheath , interanally the thin wires can break or the their covering may split causing shorts and possible issues being experienced.

Another issue is although trunk cables may look similar they may differ in wire sequence esp in the multipin green julet connector.
What isn't mentioned is the bike brand/make or the controller system used.

 

[Nealh]

I have in the past replace the said trunk cable on an internally routed bike that has had control issues and a new cable has done the trick.
It is as I have said above the bend at the bottom of the frame where it exits that is prone too shorts /intrnal cable damage.

 

[Herby]

Thanks Neal. Bike is something called. neocycle bmx stealth. 20inch fat tyre, folding bike. Said cable appears to have been squeezed when the bike has been folded/unfolded. I have examined the squeeze wires and removed the sheath around the squeezed area and while testing the continuity have jiggled the wires.. No real sharp bends.

 

[Herby]

It’s a bafang 250w motor and screen is bigstone c300s. No throttle or lights.

 

[matthewslack]

I think I would seek to find the fault, in a cautiously destructive way, on the basis that the cable is already junk so nothing to lose! That might open a door to repair, or to replacing just a faulty connector in case a complete identical cable is hard to find. All kinds of connector with wire tails can be found online or butchered out of a donor cable.

 

[Nealh]

You will have to confirm the the controller branding to see if it it a Bafang /stdz or other.

 

[saneagle]

Brake switches are by default in the on position, so yes, you should expect to be able to measure a short circuit.

There are two wires: Ground and any signal. The signal wire is held at 5v by the controller, so if you measure between the signal and and any 5v wires, you'll have continuity; however, they normally use a 5k-10k resistor to hold it up, so if you measure resistance, it should return a value in that range.

There should be no continuity between the ground and any of the others until the brake is operated. The switch connects the signal to the ground, so pulls it down when the brake operates.

You haven't told us what error codes you're getting or which wires you think are shorted. maybe an explanation would help.

 

[Herby]

Brake switches are by default in the on position, so yes, you should expect to be able to measure a short circuit.

There are two wires: Ground and any signal. The signal wire is held at 5v by the controller, so if you measure between the signal and and any 5v wires, you'll have continuity; however, they normally use a 5k-10k resistor to hold it up, so if you measure resistance, it should return a value in that range.

There should be no continuity between the ground and any of the others until the brake is operated. The switch connects the signal to the ground, so pulls it down when the brake operates.

You haven't told us what error codes you're getting or which wires you think are shorted. maybe an explanation would help.

thanks. There are no error codes. I have disconnected the main cable so there is no power running through. Also disconnected from the brakes. The red and blue wire are connected ( continuity tested).
The problem. Unable to to turn on the bike from the lcd screen on button. Bike turns on if I disconnect and reconnect the lcd 5 pin plug or if I disconnect and reconnect the battery. Battery is fully charged and after a few minutes riding the battery level indicator goes down rapidly and then no power to motor. Voltmeter shows battery is still on 54v and hasn’t gone down. The bike will turn off from the lcd screen button. New lcd screen and new controller installed.

 

[saneagle]

thanks. There are no error codes. I have disconnected the main cable so there is no power running through. Also disconnected from the brakes. The red and blue wire are connected ( continuity tested).
The problem. Unable to to turn on the bike from the lcd screen on button. Bike turns on if I disconnect and reconnect the lcd 5 pin plug or if I disconnect and reconnect the battery. Battery is fully charged and after a few minutes riding the battery level indicator goes down rapidly and then no power to motor. Voltmeter shows battery is still on 54v and hasn’t gone down. The bike will turn off from the lcd screen button. New lcd screen and new controller installed.

What you show and say are not at all clear. You show a 5-pin connector in photo 1. What is it on the other end of the wire? You also show a 1 into three cable, but they normally have a moulded round connector on the other end with 6, 7 or 8 pins depending on whether it has the connector for the throttle and separate lights function, not a flat 5-pin because the 5-pin has no brake signal wire. A 5-pin is:
Red - battery voltage
Black - ground
Blue - switched power for the controller
Green - Data receive
yellow - data send

Where's the wire for the brakes?????

If the flat 5-pin connector is on the controller and is for an LCD. The LCD shorts the red to the blue when you switch it on to provide power to the controller.

Did somebody modify something in the past because what you show is just wrong?

 

[Herby]

What you show and say are not at all clear. You show a 5-pin connector in photo 1. What is it on the other end of the wire? You also show a 1 into three cable, but they normally have a moulded round connector on the other end with 6, 7 or 8 pins depending on whether it has the connector for the throttle and separate lights function, not a flat 5-pin because the 5-pin has no brake signal wire. A 5-pin is:
Red - battery voltage
Black - ground
Blue - switched power for the controller
Green - Data receive
yellow - data send

Where's the wire for the brakes?????

If the flat 5-pin connector is on the controller and is for an LCD. The LCD shorts the red to the blue when you switch it on to provide power to the controller.

Did somebody modify something in the past because what you show is just wrong?

Thanks again. The brake wire is hidden behind my finger. It’s is a flat 5pin at one end with a 2 pin for the brakes (but just a single wire). The flat 5 pin and 2 pin connect to the controller. At the other end the green julet connects to the lcd and the 2 Red junkets connect to the brakes. Unknown if previous owners modified.
Hopefully this photo explains the connectors.

 

[saneagle]

I'm pretty sure that the cable has been butchered, and it probably means that the controller is not OEM. Where did you get this bike from? Has it ever worked? You guys always hide vital facts so that it's impossible to give sensible answers to your questions. Please tell us the whole story.

I've never seen a replacement cable like that, so buying a replacement is probably impossible. The question is why is it like that?

 

[Herby]

The whole story ?
bought it from police auction (stolen/recovered). No key or charger. Only requires key to remove battery. Bought a 48v charger. Bike worked fine for about a year. I’d say it’s about 10 years old. Then it would not turn on via the lcd screen buttons. Thought it might have been a battery issue so unclipped the frame hinge to access the battery, still fully charged ( it’s a folding bike). Re clipped the hinge and the screen came to life. Bike worked fine again but still would not turn on via lcd. LCD works to turn it off though. After each ride would unclip the hinge to disconnect the battery. After a few weeks like this the lcd battery indicator seems arted to show rapid drain of battery while riding and then no power to motor. Pedalled home manually and checked. Battery. Still fully charged. Bought a replacement lcd and made n difference. Sourced a replacement controller through Ali baba. No improvement. Checked this cable and found that red and blue wires are connected with no resistance. I assume that this shouldn’t b happening. Why would 2 wires thst are encased need to be connected ? That’s the whole story.

 

[saneagle]

The whole story ?
bought it from police auction (stolen/recovered). No key or charger. Only requires key to remove battery. Bought a 48v charger. Bike worked fine for about a year. I’d say it’s about 10 years old. Then it would not turn on via the lcd screen buttons. Thought it might have been a battery issue so unclipped the frame hinge to access the battery, still fully charged ( it’s a folding bike). Re clipped the hinge and the screen came to life. Bike worked fine again but still would not turn on via lcd. LCD works to turn it off though. After each ride would unclip the hinge to disconnect the battery. After a few weeks like this the lcd battery indicator seems arted to show rapid drain of battery while riding and then no power to motor. Pedalled home manually and checked. Battery. Still fully charged. Bought a replacement lcd and made n difference. Sourced a replacement controller through Ali baba. No improvement. Checked this cable and found that red and blue wires are connected with no resistance. I assume that this shouldn’t b happening. Why would 2 wires thst are encased need to be connected ? That’s the whole story.

As I said, the LCD connects the red wire to the blue when you switch it on. The bike will run on level 1 and throttle without the LzcD connected if you bridge those two wires, which is how we test the controller when the LCD or its wiring is suspected as faulty. There is absolutely no problem with those wires being shorted either before or after switching on, other than the controller takes a small amount of power from the battery, so will drain it if left like that fir too long (days).

I'd be looking at all battery connections, and if they're OK, you need to do a load test on the battery.

 

[Herby]

Legend. Thank you. If it’s the battery then the bike will be junk, too costly to replace a battery. I still don’t really understand why/how red and blue would be connected when the harness is not connected to anything. When reassembled If red is active and carries voltage it would already connect to blue before any buttons are pushed. Maybe thats why I hear a spark when I reconnect the battery (re-join the folding hinge).

 

[saneagle]

Legend. Thank you. If it’s the battery then the bike will be junk, too costly to replace a battery. I still don’t really understand why/how red and blue would be connected when the harness is not connected to anything. When reassembled If red is active and carries voltage it would already connect to blue before any buttons are pushed. Maybe thats why I hear a spark when I reconnect the battery (re-join the folding hinge).

You always get a spark when you connect a live battery to an ebike because its controller has large capacitors in it, which immediately charge with huge current. That spark can burn the connectors, which is probably what's happened to yours. You should always switch off the battery before connecting if it has a switch on it.

I said before that you should check that connector. The bladed ones are quite durable, but the ones with round pins on one side and thin tubes on the other are easily compromised or destroyed. I've had to replace many of them.

I'm thinking about your red and blue wires. How are you measuring the short? The result might be false. Try measuring the actual resistance between them to see if it has a high value. Those wires are connected to a MOSFET that switches them on and off. It's common for MOSFETs to leak a bit of charge.

 

[Herby]

Thanks again for taking the time to reply: very much appreciated. The cable is removed from the bike and so not connected to anything and no voltage going through. I have attached 2 pics of the multimeter reading as I connect to the terminals. I’m sure they shouldn’t be showing this reading. I don’t think it’s a false reading.

 

[saneagle]

Thanks again for taking the time to reply: very much appreciated. The cable is removed from the bike and so not connected to anything and no voltage going through. I have attached 2 pics of the multimeter reading as I connect to the terminals. I’m sure they shouldn’t be showing this reading. I don’t think it’s a false reading.

That looks like 10k, which is in the right range - nearly an open circuit, not a short circuit. Whatever reading it shows on that scale when you touch the probes together would be a short circuit.