Power the whole thing with one battery.
Soldering work should be done on the user end on the previous generation. But the Adapter 2 now has
built-in XT60 and PH2.0 connectors which both support 1-6S LiPo batteries input*. As the Adapter 2
can power your flight controller, you don't need another battery to power your quad.
*For 1S batteries, 3.8V or above is requried. Because some(very few)
quadcopters may consume a lot of current, and the output
voltage of the adapter 2 will be greatly reduced.