StorageReview checked out the Bluetti B80 Expansion Battery
A quote from the article:
The Bluetti B80 Expansion Battery is an 806Wh LiFePO4 expansion unit designed to pair with the AC60 Portable Power Station. By connecting two units to the AC60, you can get up to 2015Wh in capacity. This expansion allows you to scale power needs based on the use case, helping you save weight if you don't always need the added runtime.Bluetti B80 Expansion Battery Review