UPDATE: I found a schematic of the charger posted on reddit here. The two pulldown resistors on CC1 and CC2 negoitate with “smart” USB C power supplies for 5V, and the blue IC appears to be for overcurrent protection. My workaround bypasses several safety features, but I believe monitoring the watch while charging and connecting the dongle to the watch before plugging it in will mitigate some risk.

Charger schematic

My Pebble Time 2 stopped charging today and I figured out the charging dongle that came with the watch somehow broke. The pogo pins (+) and magnets (-) were shorted together when checking with a multimeter. Searching online shows that I am not the first person for this to happen to, and that Pebble support will generally help you out with a new charger. While waiting for that, I opened up the charger and figured the small IC on the board was shorted somewhere, as the 5V and GND pads on the USB C port were not shorted.

I cut the traces next to the pogo pins with a knife and checking the test pads indicated the pogo pins and magnets were no longer shorted together. Per the official hardware “schematic”, the watch itself has all the power and battery management circuits and just takes in 5 volts. I soldered a piece of wire between one of the 5V pads and the pogo pins. I was able to successfully charge my watch to full without any issues.

The workaround

I’m not sure exactly what the IC in the charging dongle was for, I believe either to negotiate providing 5V with smart USB C chargers, or to stop output when no watch is detected (or both). I have the dongle plugged into a USB A port so the dongle is constantly outputting 5V when plugged in. I am going to try to remember to connect the dongle to the watch before plugging it in to avoid shorting out on my metal watch band or the watch back.