Bafang M300 43V (Cortina U4) firmwares for display and controller

[LarsBeugelaar]

Hello all,

My ebike had water damage in the display. (The looks of the PCB kind of worry me. It's burnt.) I bought a new display, but I get an E30 error, with E14 sometimes for a moment. The motor does work, but the display only displays when plugging the cable, and not via the power button. (But it sort of does turn on, I can turn on the lights and plus and minus buttons vary the amount of assist. That with a blank display.) Somebody told me that the firmwares could be mismatched and it might cause communication errors. I bought a BESST and with some open source tweaking stuff I found online I got to the point that I could select firmware files to upload. All parts read out fine, but I just do not have access to these files. Can anybody provide me matching firmware files for at least the display and the controller, but perhaps also the battery, etc.? (Or maybe there is a general account going around somewhere with which I can access the cloud functionality?) I really want to avoid having to replace the motor. Thank you

 

[amberwolf]

If the display is completely blank, with nothing displayed on it at all (not just incorrect values), it may indicate a hardware problem with the display, especially since the power button doesn't work either. The power button in most of these displays turns on a tiny transistor switch that passes battery power to the system including the controller. If the controler will power on just by connecting the display cable to it, without this power-button-controlled-transistor working, then the transistor is probably failed (since they usually fail stuck on). That can just be because these transistors are often barely sized large enough to handle the normal power loads, and sometimes just randomly fail without any adverse conditions or other system problems. If the transistor is controlled by the display MCU rather than directly by the button, then it could be a failed MCU (which would also then not display anything on screen).


Mostly the firmware for any particular device isn't available, because you normally can't download it from the devices (they're usually protected against this), so except for some rare cases where someone has managed to get a FW update file from Bafang or a dealer, and even more rarely posted that somewhere, the factory/etc is the only source for FW.

Also, because of design changes over time, FW and hardware versions can be interdependent, so that only a few FW versions work on any specific HW version, and there is nothing available to tell you which are compatible except experimentation (which can brick a device if they're incompatible).

There are also multiple communication protocol versions of some Bafang systems, so different protocol versions can't talk to each other correctly or at all.

If the display you replaced the original with isn't identical to the original, I'd recommend trying to get one that is identical, if possible, to simplify the process of repairing your system.

 

[LarsBeugelaar]

Thank you for your extensive reply.
It's a bit sad to read that this is not managed better by Bafang. The embedded engineer in me is crying a bit.

The strange thing is that when I connect the plug, the display turns on, shows correct info and functions completely like it should. Then the errors might show up, but when pressing power and + buttons they disappear again and it's working fine. Then I press power to turn the bike off and that works too. Pressing again to turn the bike on, however, leaves the display blank. After doing that, the bike is on, though. I can turn the lights on and off and when I press the + button to up the assist, the bike also works like it should, with the exception that the display is blank. Turning off also seems to work, as the lights turn off after holding the power button. I have to replug the display cable to make the display show anything again. Something does not properly go into low power mode, though, as my battery was drained after a few days of not using.

Then for the display markings:

The display that came with the bike, the fire hazard one, reads: "DP.C01.C.1.0 716E1T6030296"
The display I purchased as a replacement reads: "DP.C01.C.1.0 716E1W5210306"

Not the same, but I figured it might just be a serial number.
The local wheelershop where I bought the ebike a few years ago did not have workshop time anytime soon, but reading your story about the hardware and software management of Bafang tells me that they would also be guessing at it and I doubt they have a true specialist running around who knows these ins and outs.

I kindly requested a BESST account for software updates from Bafang for the purpose of fixing my bike after their product started burning in my house. I wonder if they will reply and/or grant.

Can you/somebody tell me if the displays with markings shown above should be interchangeable?

Thank you

 

[amberwolf]

Something does not properly go into low power mode, though, as my battery was drained after a few days of not using.

Do you read any voltage at the motor controller itself in this state (when it should be off but isn't really)?

If there's no easy place to test at the controller, you could modify an extension cable between controller and display so you can access wire conductors on at least the ground and Battery + and "keyswitch / ignition" + wires. You should only get battery voltage across ground and B+, not on KSI, when the system is off. When it's on, you get BV at KSI too, as this feeds the controller's low voltage power supply LVPS and turns on the controller brain.

If there is BV at KSI then the controller's LVPS and brain (and anything powered from it, like hall sensors, PAS, throttle, etc) will have some drain, from a few dozen up to a few hundred mA, from the battery, so in a day you could lose a couple of Ah or more from a battery.

Another place to test for KSI being on is the 5v at hall sensors, PAS, throttle, if you can unplug one and can reach the contacts inside the connectors (might need very tiny conductors to fit in the pin holes). They only get 5v if the controller LVPS is on, which only happens if it gets BV from the display's KSI wire.


If there is voltage at any of those, then the display is not turning off the KSI transistor switch, whcih usually means the switch is failed (shorted on).


The displays should be electrically compatible, most likely, even if for whatever reason their firmware doesn't have identical comm protocols or menu settings/values/etc, so that would not affect the above, even if it affects what the display shows.