This is the Shimano SM-BTR1 Di2 Battery. 

Features:

• Di2 External Battery, battery charger, and power cable are universal between Dura-Ace 9070, 7970, Ultegra 6870, 6770 and Alfine Di2 systems
• Weighs only 71g
• Lasts around 1,000 miles on average
  

Specifications:

Type: Lithium Ion

Nominal Capacity: 530 mAh

Weight: 71g

Operating Temperature Range: -20 – 60C (when discharging), 0 – 45C (when charging)

Storage Temperature Range:  -20 – 60C

Nominal Voltage: 7.4V

This product was added to our catalog on July 26, 2014