Battery life is something that a lot of potential Di2 or EPS (and now SRAM eTap of course) customers consider before taking the plunge. How many miles am I going to get? Will it suddenly go flat mid ride? Is there any warning?
I’ve been riding Shimano’s 10-speed Ultegra Di2 since late last year and have covered quite a few miles on it now. I absolutely LOVE IT! It hasn’t missed a beat, is a real pleasure to use and most of all makes you feel totally pro.
With Shimano, you get a nifty little indicator light on the stem-mounted junction box to let you know roughly how much charge is remaining. Press the shifter paddle for a second or two and it lights up in one of four different sequences:
Solid green = From 100% down to 50% battery level remaining
Blinking green = Around 50% remaining
Solid red = Around 25% remaining
Blinking red = Charge me now!!
Even on blinking red you still have (apparently, I haven’t tested it out) over 200 shifts left before completely draining the juice. When it gets really, really low, first the front derailleur quits shifting, then after a couple of hundred more shifts the rear derailleur stops in whichever cog you happen to be riding at the time. From then on you’re single-speeding home!
From a 100% charged starting point, the indicator light on my system changed from solid green to blinking green at 750 miles (1200km). I do change gear quite often, but not so much on the front which requires more battery power.
After 1030 miles (1650km) the indicator light changed to solid red. Not wanting to chance it, I then charged the system up to 100% again! Charging is simple enough. A port on the side of the junction box connects to a USB cable so you can charge from your computer/laptop or any other USB point.
I’m guessing the battery would be good for 1300 miles on a single charge, probably more. That said I’d be inclined to charge it as soon as you hit solid red – maybe sooner if you’re planning some really long rides. So there you go, as long as you’re sensible and keep an eye on that all-important indicator, there’s no reason for your Shimano Di2 to ever run out of juice while out on a ride! Just keep an eye on that light!