Pixel 3aΒΆ

You can see the battery below, with the yellow kapton tape that insulates the BMS from the battery connectors. Carefully remove all of it.

Battery

Once the pads are soldered, it looks like this.

BMS

The BMS fits neatly into the battery compartment even after removing the battery itself.

motherboard

To get the cables out of the device, you can drill a hole in the back cover

back cables