Get a plastic spudger and push upwards on the underside of the connector

Then unscrew the battery from the body.

Then you can remove the battery by simply lifting it out of the case.

DO NOT use metal pry tools or try to pry the battery out with them if it is stuck. Use gentle pressure with a plastic pry tool to pry the battery out.

You will want to remove the battery first to remove all power from the device so you don't short or damage anything inside.