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Shimano Dura Ace DI2 Battery Life
The Shimano DuraAce DI2 shifters are electronic, so there is a battery involved. The 71g and 0.53 amp-hour SR-BTR1 lithium ion battery allegedly lasts for months, so charge it every 400 miles, and you’re Good.
A full charge takes 1.5 hours with the SM-BCR1 charger. I would have preferred a more compact charger, instead of one with a long power cord that plugs into a 10 X 7 X 3 cm base into which the batter slots— this stuff has to be packed on a trip.
On the Trek Madone 6.9 SSL, the battery isn’t visible; it sits under the bottom bracket using a built-in mounting setup.
Real world battery life
Be realistic based on your riding style— I’ve heard “3-6 thousand miles” which is wildly at odds with my experience, and is also at odds with the Shimano battery manual, which states that about 780 miles of riding is possible:
Whoever gets 3-6 thousand miles of battery life must be shifting 1/4 to 1/8 as often as I do, which is weird since one of the advantages of DI2 shifting is super fast and simple shifts, so as to achieve just the desired cadence.
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On my Trek Madone 6.9 SSL at mile 1053 (853 miles since the last charge), the front derailleur would no longer operate, and the battery status light was red. The rear derailleur continued to shift for the remainder of the ride.
I charged when new, and after about 200 miles, giving me about 850 miles of shifting life on the battery before it refused to shift the front derailleur. That’s very close to the 780 mile figure that Shimano claims.
Therefore, I offer the following rule of thumb for avoiding the battery every dying unexpectedly: