Either battery or Omron recharger.

The device could also be operated with a power supply unit, but this is not included in the scope of delivery and is not necessary.
The battery consumption is surprisingly low, I can't remember the last time I changed the batteries.

Hoi Magistratus
Your question had me wondering at first glance because, lixunjack writes, it runs on 4 AA batteries. Then I saw in the product description at Galaxus: "Battery operated". That seems to me to be a mistake. I have just reported it.
Greetings

You do not charge it. You will need four A4 batteries or so.