Display suddenly shows empty battery

[Keldin]

I'm hoping someone can help me with a sudden fault that appeared yesterday. My folding bike has a battery and controller in the rear bag that means disconnecting and removing when folding.
There are 3 cables (pedelec, motor and the display/brake/throttle). Had 3/4 battery when i did this yesterday morning after getting to work and when I reconnected in the evening the display turns on but showed the battery gauge as empty. No motor response to throttle or pedalling.
The battery is charged (charged it overnight again) and the connections all seem good as far as I can tell. It's only done 20 miles so far.
Does anyone have any idea of what could cause this?
Thanks

 

[Nealh]

As all was well prior to disconnection it may be a wiring/connection fault, either a broken wire or a faulty/bad pin/connector. I would test the wiring starting at the battery end first then work my way through the other cables/leads systematically. Another thought check for a blown fuse first most battery's will have one, other wise something may be wrong with the battery.

 

[patpatbut]

Having a multimeter helps a lot to find out the fault. Starting with the battery and check the voltage.

 

[Keldin]

Voltage showed 38.8 when I tested it part way through charging. Didn't have time this morning to test it after the overnight charge but assumed 38V should be enough for a 36V battery?
Not sure how to test the wiring but I'll open up the controller and see if there is a fuse in there.
Thanks

 

[Keldin]

I'm pretty sure something happened with the wiring. I may have done something wrong when connecting up again in the evening and possibly bent a pin or something. Battery seems good and unless there is some feature of Li-Ion batteries in ebikes that I'm unaware of I would expect the display to show some charge level considering the voltages I'm measuring.
I'll read up on troubleshooting cables and concentrate on that.

 

[KirstinS]

Voltage showed 38.8 when I tested it part way through charging. Didn't have time this morning to test it after the overnight charge but assumed 38V should be enough for a 36V battery?
Not sure how to test the wiring but I'll open up the controller and see if there is a fuse in there.
Thanks

No, both your charger and your battery should read 42v or very close

The charger always 42v and the battery 42 hot off a full charge

 

[KirstinS]

Having a multimeter helps a lot to find out the fault. Starting with the battery and check the voltage.

Personally I'd start with the charger - make sure it reads 42v

Next the battery - should be 42 directly after a full charge

 

[KirstinS]

I'm pretty sure something happened with the wiring. I may have done something wrong when connecting up again in the evening and possibly bent a pin or something. Battery seems good and unless there is some feature of Li-Ion batteries in ebikes that I'm unaware of I would expect the display to show some charge level considering the voltages I'm measuring.
I'll read up on troubleshooting cables and concentrate on that.

Best to do things logically despite your sensible hunch

Charger, then battery (full) give us the results and then we. Can work from there

 

[Keldin]

Charger is 42V. Battery is 41.8V after being off the charger for 12 hours.
I can't see any problems with the wiring and all the connections seem good.

 

[Nealh]

Problem with wiring is it is almost imposs to see any thing wrong, so testing with a multi meter will show up any poor/ negative readings.

 

[Michael0987987]

I had the Same problem I turned my e bike off to put pas sensor on an after doing that I realised I done it backwards when I took it off I noticed my led battery indicator was empty but my battery wAs full an no throttle response any help please??

 

[manman94]

Have LCD 8 display with KT controller problem is when riding it takes 20 seconds or more before the display shows speed,any ideas please

 

[manman94]

My bike has a bafang 250w 36v rear hub motor

 

[saneagle]

Have LCD 8 display with KT controller problem is when riding it takes 20 seconds or more before the display shows speed,any ideas please

Remind us whether you're using a speed sensor or not.

 

[manman94]

Oh yes sorry no I dont have a speed magnets sensor on the wheel but i do have the white wire connector