I can confirm that the battery is included.

What is missing for the installation with the PC is a printer cable.

A rechargeable battery is already included.

Scope of delivery:
HP OfficeJet 250 all-in-one mobile printer
HP OfficeJet 200 series battery
HP 62 Black setup ink cartridge (approx. 200 pages)
HP 62 Cyan/Magenta/Yellow setup ink cartridge (approx. 120 pages)
Software CD
Installation poster
Power cable