The power supply for your SwissKubik automatic watch winder will depend on the model you own.Startbox: This winder runs exclusively on batteries (2 C 1.5 volt alkaline batteries - we recommend using Duracell Procell batteries for their quality.)Masterbox: Offering greater power versatility, this winder runs either on mains power or batteries (2 C 1.5 volt alkaline batteries - as with the Startbox, we recommend using Duracell Procell batteries, but others brands also work). The Masterbox demonstrates built-in intelligence by automatically detecting a mains power source: when plugged in, it automatically switches to mains power, preserving its battery life. Similarly, as soon as the watch winder is unplugged from the mains, it automatically resumes battery operation for uninterrupted use. Please note that the USB-C port is a simple power supply used to plug your watch winder into the mains; it cannot be used to recharge batteries. It can also be used to programme your winder via our Mac/Windows app.Whether you opt for the Startbox or Masterbox automatic watch winder, we recommend that you do not use rechargeable batteries.