I keep bikes in the basement, have a cabinet top where I've a 4 port USB outlet unit plugged into an extension cord. It has my Di2 charger and my Garmin cable.

I know now from hard earned lessons to only use this particular USB cable when doing anything with the Garmin, specifically updating software from my laptop using Garmin Express. Then the cable goes right back to the charger USB. Seems not all USB Micro (or whatever the Garmin port is, Mini maybe ?) can deal with data and I've tried half dozen cables before finding one that works. That's now the Garmin Cable.