To get a feel for Di2 battery life, I’m tracking the number of days as well as the number of hours the trike was moving (and therefor shifting and with the display on) between each charge. The chart at the top shows the distance and number of days between charges since I settled on a consistent configuration: Ultegra derailleur and Alfine display programmed to turn off after 5 seconds. A discharge cycle for this graph is from full charge (4 bars) to 1 bar. I figure in practice I’ll recharge as soon as I hit one bar so that I have an entire bar of “fudge”. So the time between charges shown in the graph should be easily attainable, repeatedly.
The charts show the run down for the first four discharge cycles of the battery’s life, spanning all four seasons in the Boise high desert. For the first two I ran it all the way to zero bars and dead battery just to explore the limit, and to get a feel for how much fudge that last bar provides. The third cycle represents how I plan to manage charging here on out: when it hits 1 bar, charge it when I get a chance, knowing I should have at least a couple weeks grace period. I’ve also plotted each day’s maximum and minimum outside air temperature in an effort to determine how much temperature affects battery life. The trike is stored in an unconditioned garage and parked outside at work.
I’m no longer concerned about battery life, though the first discharge cycle had me worried. 35 days between charges is pretty good, but only 17 hours of total ride time in that period is really low. On a tour I could use this up in a few days. Thankfully the combination of warmer temperatures, Ultegra derailleur instead of Alfine motor, and 5 instead of 300 seconds display time have all contributed to a substantial increase in battery life. 3 months, 700 miles, and 64 hours moving during prime touring season is fantastic. Granted these were all commuting / recreational miles, so maybe a month on the road before even having to think about charging. I can live with that.