The Phase One XT is designed from the ground up to be a field camera, and when you take a camera into the field for long periods power is always a concern.
The Internal Battery
The Phase One XT body and Phase One XT lenses draw their power from the Phase One IQ4 digital back. That means the entire system requires only a single battery (inserted into the Phase One IQ4) for power; the XT itself does not have or need a battery. The battery that goes in the IQ4 weighs just 100 grams and costs just $70, making it easy to pack a few for a longer trip.
External PowerThe IQ4 Infinity Platform accepts power through its USB-C port and Ethernet port (via POE). In the field, that means you can use one of any number of external power packs rather than changing out the internal battery. These power packs are relatively inexpensive and commonly used to charge phones while on the road, and so are often already in a photographers travel kit.
You can read more about USB-C Power Options here.