The front (if applicable) and rear derailleurs each have one rechargeable lithium-ion battery. These batteries last about 60 riding hours on a full charge. A full battery charge takes about 1 hour and is done using the eTap USB charging cradle.
How much battery life is left?
Every time you shift, a light will flash on both the shifter and derailleur.
Green = up to 75% battery charge remaining.
Red = 10-25% battery charge remaining.
Flashing Red = Less than 10% battery charge remaining.
To prevent battery depletion and to protect the components, install the derailleur battery blocks and battery contact covers before transportation.