The e-bike that wouldn‘t

Oftentimes I encounter problems that I never imagined one could have.
Like: „my bike doesn‘t turn on“.

Yeah. So my awesome e-gravel-bike that I got this summer seems to have an issue. And if I still had hair… I would be pulling it out over this.

Trigger warning: the issue isn‘t solved yet. I can only tell you some fun things I found out so far…

For reference: my bike uses the 2025 Bosch Smart System, with the Performance Line SX Motor. It has no display other than the „System Controller“ (two buttons and a few LEDs), and via Bluetooth connects to the Bosch Flow App.

What is wrong?

After my last ride, I plugged the charger in the bike. Roughly two weeks later, just about to take it on vacation - It doesn‘t turn on.… in many different ways. When I push the power button, either of these versions has happened, and for the life of me, I cannot yet troubleshoot what happens when.

1. Shows the startup sequence of blue charging indicator LEDs, blinks all white (signs that the security module seeks connection to my phone to unlock it), then it shows a yellow status light with one red bar where charge would be shown.
   Web says: „there is a non-critical issue“ when the status lights shows yellow. Red would indicate „critical“. Then it shuts off again after a few seconds.
2. Startup sequence - then blinks white for a few minutes (can‘t be shut off by pushing buttons), then stops.
3. Startup sequence, blinks white a handful of times, then shows the „shutting down“ sequence of blue charging indicators.
4. Startup sequence, blinks white, then goes to drive mode color purple (these are blue, green, purple, red for the modes) and red charge indicator. Switches on the bike lights for a second. Then immediately turns off (shutdown light sequence.
5. Randomly, between these tries, it has switched the bike light on and off (without any activity visible at the system controller)

Now, what has the Flow app told me?

I should have taken screenshots or screen recordings of course… will have to do this for round two of this misery. But remember, I am on vacation! I just wanted to get my bike in working order and hit the trails. So, from memory:

• It started with a notice that the connect module (the GPS tracker/ security module oft he bike) would only give hourly status updates due to low battery.
  -> This lets me believe that somehow the bike‘s battery got discharged, despite me having it connected to the charger
• It sometimes scolded me for disconnecting the battery (which is built in, I have to disassemble the motor completely to even start getting to the battery…
• It once told me some other error pertaining to the connect module and the battery, but only for a few seconds…
• Every time the controller on the bike was blinking, it also connected to the phone app
• Sometimes it activated the alarm, because it still registered me moving the bike, but did not power on long enough to actually „unlock“ it.
• Two times I was able to be quick enough to click the „all is good, I got my bike“ button - currently the app again tells me that my bike might be stolen and is in „tracking“ mode.

What else did I observe?

• Connecting the charger to the bike does NOT make the charge indicator LEDs blink.
• The charger seems to be working though, because it does charge the Range Extender which I also have.
• Connecting the range extender to the bike first did not change anything (seemingly same erratic behaviors from list above) compared to being on the built-in battery. Sadly, even with the fully charged range extender, the bike did not turn on - even when the flow app correctly showed the charge at 94%.
• After a while, the bike did not turn on anymore at all when the range extender was not connected.

What hints did I get in addition?

• I learned that the controller itself has a battery, which charges from the bike battery, only when the system is in use. In storage, it can discharge. You can then actually charge it directly via USB-C (luckily, it is only one Torx screw to get to it).
  -> did nothing though…
• I learned that sometimes the connect module acts up, and it can be reset by pushing a physical button (this is a manual showing what it looks like, where it is connected to the bike, and where the reset button sits)
  -> did nothing though….
• I learned that the bike can be „reset“ by pushing the power button for 14 seconds or longer. Tried it. Did not change anything really.
• I learned that the battery can be reset separately… this I have yet to complete, because I did not have the nerves to fully disassemble the motor, all cables, etc… in the entrance of our vacation home, instead of, you know, actually enjoying my vacation.

So, where do we stand:

• Totally useless error codes in the app, no real logic to the behavior displayed by the bike.
• I now own a new set of Torx bits, because I did not have a T40 with me to get the motor unscrewed. There do not seem to be obviously loose connections.
• It is not an undercharged system controller, and a connect module reset could not fix it
• My hypothesis:
  • The battery does not take charge. Something in how the bike distributes energy seems out of whack - otherwise it would work when I connect the Range Extender.
    -> I have no means of troubleshooting this. The only thing I might try myself once I have returned home is to get the motor out completely, get the battery out as well, and see if there is a button to reset it / if I can directly charge it with the charger (haven‘t checked if the connectors match). If this does not work, it will go to the bike shop….
• Sidenote: when the bike was first delivered, there was an issue with the bike‘s lighting system not being properly connected - this was fixed by the shop that delivered the bike. Maybe something to do with that?
• Luckily, there are three electrical component not powered by the bike‘s system: the dropper seatpost and the shifters. And luckily, the rear derailleur can be disconnected from the bike‘s power and take the same battery which the seatpost uses.
  -> After all, the bike was rideable!

To be continued :)