The Shimano Dura-Ace Di-2 Battery Charger is made specifically to charge the Di2 battery. It fully charges the battery in 60 to 90 minutes. One the battery is fully charged, Shimano claims it will last up to 1000 miles. That is a lot of shifting!
Handy charging light display show when the battery is fully charged and ready for use. For some reason, Shimano decided not to include the power cable, so it must be purchased separately.
Please note: battery charger only. Battery and charging cable sold separately