My headlamp wouldn't charge until I did some difficult soldering

To trigger a charge, a USB-C device has to have a 5.1k ohm resistor on each of the two CC pins. Whoever engineered this headlamp neglected to include them, even though the connector had the pins. This means that USB-C chargers will see no resistor and assume there's nothing to charge. After some difficult soldering, I bodged in one of the two resistors, allowing it to charge in one of the two cable orientations.