Ember Mug: What type of battery does it use? The Ember uses dual lithium-ion batteries. Related articles Ember Mug: How long does it take to charge my Ember? Ember Mug: What is the temperature range? Ember Mug: Can it charge while actively heating my drink? Ember Mug: Will the battery discharge when in sleep mode? Ember Mug: Can it be used to warm up drinks from room temperature?