Early Di2 systems from the Dura-Ace 7970 and Ultegra 6770 era mounted their batteries externally, typically clipped to the underside of a chainstay or tucked behind the seatpost. The SM-BCR1 is the dedicated charger for that SM-BTR1 external battery. Unlike the newer SM-BCR2 that charges through the junction box, this charger works as a standalone dock: you pop the battery off the bike, slide it into the cradle, and plug in.

The charging process takes 60 to 90 minutes depending on how depleted the battery is. An orange LED stays lit during charging and turns off when the cell reaches full capacity. Once topped off, the SM-BTR1 typically delivers around 1,000 miles of shifting before needing another charge, though heavy front derailleur use can shorten that range since the front mech draws more current than the rear.

Shimano sells the charger and power cord separately, which sounds inconvenient until you realize it lets the same charger work anywhere in the world. The SM-BCR1 is the dock unit with the battery cradle and charging circuitry. The SM-BCC1 power cord, available with plug configurations for different regions, connects the dock to your wall outlet. For North American customers, the SM-BCC1-2 provides the correct plug type. If you're traveling internationally with a Di2-equipped bike, you can carry the same charger and swap cords rather than packing a voltage converter.... Read More