Hi, thanks for providing the details of your experience, The current with the default bootloader is around 3-6mA from battery taps. I think the 60mA is from the USB port that includes a battery charging current of around 50mA. and about the programming the sense-ble by a raspberry zero, it is another headache, they are out of stock as far as I see. What I have found is we should be able to go to bootloader mode and just replace the uf2 file but I am wondering why seeed’s wiki does not mention that at all!!!