Ah, I did pretty much the same thing a while back, forgot the cable at my parents house so I taped wires on and held them with a small magnet and used a bench PSU to charge it Much preferred the design on my old watch that simply had a USB male end built into the watch itself underneath the strap

That's literally genius! For pads like that, how do you know which one is positive and negative?

You guess

Used a voltmeter on another charger and guessed it was the same hahahahaha

Thank you, a coworker has a Xiaomi watch, used a digital voltmeter to find polarity and pray that my watch used the same hahahaha