The Atomos Shinobi II can be supplied with power in several ways, so that a separate battery is not absolutely necessary, but can be used as an option.

1. USB-C PD: The Shinobi II can be powered via the USB-C port, which is a convenient option, especially if you also want to charge your camera device via the same port.
2. NP-F battery: The monitor can also be powered by an NP-F style battery, which is a good option for longer-lasting shots.

This means that a separate battery is not absolutely necessary, but it offers flexibility and longevity in terms of power supply.