Battery display shows empty on fully charged battery

[Gobbledygook]

Hi, I'm hoping someone can help with my problem as I'm stumped.

TL/DR The display on my LCD shows zero bars even though my 36v battery is providing 41.5v. The bike therefore won't power by throttle or when peddling. Any ideas what's wrong?

Long version: Cyclotricity 250W front wheel drive kit.

Worked fine for years, then there was an intermittent power problem (LCD occasionally powering off completely) which I traced to the main system cable. I replaced this and the battery indicator on the LCD showed no bars even when the battery was fully charged (all LEDs on the battery indicator are lit, 41.5v measured at the battery, the end of the main system cable and even on the circuit board inside the LCD when I took it apart). The bike therefore won't power by throttle or when peddling.

I assumed there was now an LCD fault so bought another one from Cyclotricity. When this was plugged in, the battery tripped (could be reset by turning it on and off), and kept tripping until I unplugged the controller. It's possible my dismantling of the old LCD resulted in controller damage, so I bought a new controller from Cyclotricity and the battery no longer trips, but both my new and old LCD show zero bars even though my 36v battery is providing 41.5v. I setup the P values on the new LCD as per the old (P1=87, P2=1, P3=1, P4=0, P5=12)

I contacted Cyclotricity and they talked me through some fault finding and then recommend replacing the system cable. I explain that this is already new, but they insisted it must be at fault. I belled out the cable and there's no fault, so I sent them back the LCD as I suspect it could be faulty. They send me a new LCD, with no comment as to whether the old one was faulty, and the replacement shows zero bars just like the other two!.

I've tried various P5 settings but no joy. Could a faulty battery or faulty motor cause this? I don't want to buy any more parts until I know what's wrong. Any ideas on how to diagnose this?

 

[docw009]

My experience relates to KT controllers and displays, Sounds like you have a variant with the same P values.

Even though my LCD5 passes thru the battery voltage, it needs data packets from the controller to show the battery icon and also the speed. I've had a couple of cases (two different bikes) where the receive data line from the controller was broken. These bikes didn't have a handlebar harness. The display cable went directly to the controller, and the round WP connector changed to a flat JST 5 pin.

However, my bikes worked even though speedometer and battery icon were off, and I don't know why they didn't show a Comm Error as you would expect.


Now your bike display is powering up, so it's getting 36V, and you have checked it on the display connector? If it powers up, it sends battery power to the control pin to turn on the controller, See if you can find a way to measure that. One way to infer that is to check your throttle connector for voltage.

Another approach is to bypass the display, If this is a KT model, jumpering control to battery will do that. Here's how they do it with the flat display connector, They even ship that jumper plug with certain bare controllers,


It also works with the round connector, By the way, I have also done this with ebikeling controllers, a brainpower controller with the S866 display, and a Bafang BBS02 mid drive. They use the battery and control pins to start the controllers. In all theses cases, the controller has throttle and PAS,

If you do not have a KT controller, well, you're on your own,

 

[amberwolf]

What happens if you discharge the battery down to say, halfway, then power everything off, disconnect the battery for a long while (day+), and then reconnect the battery?

There are some systems that can operate on either 36 or 48v that autodetect which pack is there. At full charge a 36v battery looks like an empty 48v pack to some of these, which then think they have a 48v pack not a 36v, and so now the battery meter shows empty. So it could have gotten into this condition, and sometimes can be reset by the above method, or others I don't recall ATM.

 

[Gobbledygook]

Thanks, that's brilliant!

The controller is a KT36ZWSR, so I'm in luck.

From the LCD I have dismantled there's only one wire with 41.5v on it. It's a red wire inside the LCD so l hope they are using the same convention as in your picture. The pin marked 'control' in your picture is connected to a blue wire. Other wires are black green and yellow, so it looks like it matches your colour setup.

I've got the round connectors, so I'll try connecting red and blue inside my old LCD and see what happens. If nothing I'll then connect yellow to ground and try that.

It will be next week before I can try it, but I'll report back when I have.

 

[Gobbledygook]

What happens if you discharge the battery down to say, halfway, then power everything off, disconnect the battery for a long while (day+), and then reconnect the battery?

There are some systems that can operate on either 36 or 48v that autodetect which pack is there. At full charge a 36v battery looks like an empty 48v pack to some of these, which then think they have a 48v pack not a 36v, and so now the battery meter shows empty. So it could have gotten into this condition, and sometimes can be reset by the above method, or others I don't recall ATM.

I'll give it a go. They sell both 36v and 48v batteries but only one LCD, so it must autodetect. I can't discharge the battery using the motor, but I'll try dropping some voltage by charging something from the USB.

 

[amberwolf]

From the LCD I have dismantled there's only one wire with 41.5v on it. It's a red wire inside the LCD

Virtually all of these systems use the same 5-wire convention, B+ from controller, B+ back to controller on "ignition" when you turn on the display, TX, RX, and B- (ground). The protocols and data used on the TX/RX are quite varied, making intercompatibility rarer than it should be, but the rest are the same.

However, wire color varies widely, so don't go by color--go by the pad with the correct marking on the PCB, or by which pin on the connector they used (for those you can find a pinout for) etc.

 

[Gobbledygook]

Thanks, I'll examine the PCB first and see if I can decipher any markings.

 

[amberwolf]

If you post a pic we can make educated guesses.

 

[Gobbledygook]

I found the problem, one of the pins in the connection between the system cable and controller had bent when I fitted the replacement system cable , so wasn't making a connection. Bent it back and my new LCD now works as it should.

I noticed when I was belling out the cable into the old broken control unit that there was a score down the inside of the connector, caused by the bent pin, which sent me to look at the connection between my new controller and new system cable - and there it was.

Interestingly, my old LCD still displays no battery bars when I plug it in, but the new one works fine so I'm happy. Might plug the old one back in when the battery is half drained and see if it makes a difference.

To complete the thread, for anyone else who comes across it while searching, the wire colours inside the LCD connect through to the circuit board in the controller marked as follows:

Red = g (this was the live wire at 41.5v)
Black = N
Green= TX
Blue = DM
Yellow = RX

Assuming DM=Control, the location of the pins in the Juliet connector also match those in the picture, so there's a very good chance if I'd tried the bypass based on docw009's pictures, it would have worked.