Travel mug: What type of battery does it use? The Ember uses dual lithium-ion batteries. Related articles Travel mug: How long does it take to charge my Ember? Travel mug: How long can I expect my battery will last? Travel mug: Can it charge while actively heating my drink? Ember Mug: What is the Charging Coaster Voltage? Travel mug: Can I put my Ember in the microwave?