How do I update the firmware of DJI Power 1000 V2?

You can update the firmware through DJI Home app and DJI Assistant 2.

DJI Home app: After connecting the DJI Power 1000 V2 to the app and configuring the Wi-Fi network, go to Settings > Firmware Update to upgrade to the latest firmware version. DJI Assistant 2: Refer to the Firmware Update section in the user manual. Before the update, install DJI Assistant 2 (Power Series) on your computer.