Battery Morph Coffee & Beverage Heat Sensitive Color Changing Mug Nothing is sadder than an empty battery. All cold and lifeless, it needs rejuvenation. Luckily, you filling up your cup juices up morph mug battery! As the morph mug battery gets hotter, its energy level increases. This charming display of vitality also lets you know that your beverage is still hot hot hot. This coffee mug is heat sensitive and color changing. The battery is white until you pour a hot beverage in the cup and the battery turns green.