I have a power bank that makes a Mobius think it is connected to a computer and forces it to go into standby mode rather than begin recording. Some "smart" power banks will cause this issue unfortunately. The solution has been to modify the existing cable by cutting the white and green data wires while leaving the red and black power wires intact.( You will probably need to completely isolate the shielding from the connection as well.)
If you happen to have a short spare USB-A to mini-B cable around you can try this fix-it out and see if it works for you before committing to the cable you want to use on your bike.
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Mobius doesn't see my power bank as a computer. As I said in my previous comment, Mobius stays in standby mode forever when indeed connected to a computer, while when connected to my powerbank then Mobius auto shutdowns after 30s (my settings to save battery if not recording btw), then the powerbank also auto turns off. So my current wish is for the powerbank to continue charging Mobius even when Mobius is off. Not quite sure which powerbank should I buy to solve this