The Shimano SM-BTR1 is an external, rechargeable lithium-ion battery engineered specifically for use with Shimano Di2 electronic shifting systems. Designed for frames that do not support internal battery routing, this battery installs on the down tube or seat tube using a dedicated mount. The SM-BTR1 is well-suited for cyclists who rely on electronic shifting but ride older models or frames lacking integrated battery compartments.

Compatibility is broad: the battery works with a variety of Shimano Di2 groupsets, including Dura-Ace 7970, 9070, R9150, Ultegra 6770, 6870, R8050, GRX Di2 RX815, Alfine/Nexus Di2, XTR Di2 M9050, and XT Di2 M8050. This makes it ideal for upgrading or maintaining older Di2 systems, or for use with cyclocross, gravel, or road bikes equipped with external wires.

With a 7.4V nominal voltage and a 500mAh (3.7Wh) capacity, the battery typically delivers between 1,000 and 2,000 kilometers of reliable shifting per charge, depending on usage patterns and environmental conditions. Charging takes about 90 minutes using the SM-BCR1 charger. At only 70 grams, it adds minimal weight to the bike. The SM-BTR1’s sealed plastic housing ensures durability against the elements, and its simple setup makes it a practical choice for both mechanics and DIY users.

This battery is best for those who value straightforward installation, versatility across Shimano Di2 systems, and the ability to keep older electronic shifting setups running smoothly.