One of the most common concerns with the Shimano Di2 electronic shifting system is, of course, what happens when the batteries lose charge. Fortunately, Shimano has the answer. It's called the Shimano Di2 Internal Battery Charger. With a charge time of just an hour and a half, you won't ever miss a ride because of charging. The charger is made to accommodate both internal or external battery systems by connecting to the SM-EW90 junction box. The charger also has two indicator lights--one that tells you when it's charged or charging, and one that tells you if there is a problem with the battery or system.The Shimano Di2 Internal Battery Charger comes in one size and in the color Black. Confused about how to build your Di2 Kit? Read our Learn Article.