Insert the point of a spudger under the edge of the battery connector head opposite of the cable.

There's a surface-mounted component close to the connector. Be careful not to touch it with your spudger!

Lift up the connector with the spudger to separate the rest of the coating and disconnect the battery.

During reassembly:

Inspect the connector head and its socket for any remaining coating that could prevent a good connection.

Peel off the coating, heating the area when the coating becomes too brittle.

It doesn't have to look pretty! You just need to remove enough coating so the connector head sits properly in its socket.