Having this same problem and did some research into trying to replace the Ember Mug internal battery. Another Reddit post I found ([link|https://www.reddit.com/r/JamesHoffmann/comments/s79huz/long_term_experience_with_a_14oz_ember_mug_2/|https://www.reddit.com/r/JamesHoffmann/comments/s79huz/long_term_experience_with_a_14oz_ember_mug_2/|new_window=true]) states in one of the comments by the OP: "This applies to only the travel mug - the regular mug is molded closed and can't be opened without destroying it" I also found the FCC page for the Ember Mug ([link|https://fccid.io/2AILTCM17/Internal-Photos/Internal-Photos-3517267|https://fccid.io/2AILTCM17/Internal-Photos/Internal-Photos-3517267|new_window=true]) that shows the Battery and other internal electronics but without a way to open the mug and replace it I'm not sure this information is useful... If the Mug ever stops working completely destroying it might be a risk I'm willing to take but for now it seems to be unrepairable.