The Shimano Di2 SM-BCR1 External Battery Charger is made specifically to charge the original external Di2 battery. The battery itself is removed from it's clip-in mount, then popped into the charging dock, which is designed to fully charge the battery in 60 to 90 minutes. Once the battery is fully charged, the battery will generally last for up to 1000 miles of use.

A handy charge display indicates when the battery is fully charged and ready for use. This is just the charging dock. Shimano sells the charger and AC cord separately due international distribution. For the US and Canada, you need to purchase the SM-BCC1-2 Battery Charging Cord, which has the US 2-prong plug design.