A Year of Di2

A year ago today I began running Shimano Di2 electric shift on my recumbent trike.   I’m pleased to report it has exceeded my wildest expectations.  But like most aspects of this now multi-year project, there were problems in the beginning.

My initial build was with the Alfine-11 hub.  When running nominally, this is still the best shifting I’ve ever experienced.  Silent, instantaneous, ergonomic, with all the benefits of an internally geared hub.  And, unfortunately, all the problems.  As I’ve reported ad nauseam in earlier posts, I dumped Alfine when Shimano’s indifference became apparent after my hub failed within a couple hundred miles.  Fortunately I was able to keep the electric shifting by switching to Ultegra Di2.

While running Alfine I experienced disappointing battery life.  This problem resolved itself through some combination of warmer ambient temperatures, a few discharge cycles, running with the minimum 5-second timeout on the gear display, and the switch to Ultegra.  After a year, I appear to be getting roughly 3 months between charges for my daily commute.  A few weeks longer than that if I were to take the battery all the way to empty; I recharge when the battery indicator goes to 1 bar.   Details of my battery life are here.  I summarize my experience with Di2 like this:

When new, Ultegra Di2 shifting is significantly faster, more precise, and quieter than any rear derailleur I’ve ever used, and remains that way, whereas performance degrades with each shift of a system with mechanical cables.  After about three months with mechanical cables, the typical interval of winter commuting before I can’t stand my crappy shifting any longer, I’m faced with either re-lubing or replacing the cables.  Now in that same interval I just plug in a charger overnight.

But it’s better than that.  In addition to the aforementioned benefits, I’ve replaced my crappy mechanical twist shifter with a vastly superior Alfine pushbutton shifter.  Of course Shimano’s part in this was accidental, but the design is just about perfect for the typical recumbent under-seat handlebar arrangement.    Before installing Di2, I fully intended to develop a high quality Di2 twist shifter.  We can debate the merits of that fantasy, but after using the Alfine Di2 shifter with my Ultegra Di2 derailleur, the project is no longer on my list.  It would be a major development effort that would at best achieve only a modest improvement over what I’m running today.   I’ve got better things to do.

I’m sure reliance on a battery is what keeps some people away from Di2.  While I believe the benefits far outweigh the minor drawbacks, I must admit I’ve witnessed two issues with the battery.  The initial concern over battery life, now resolved.  And this:  My brother, who did exactly the same Ultegra Di2 install to his nearly identical trike, wound up installing a Di2 battery that was DOA.  It worked normally for a short while, then began discharging rapidly, and eventually wouldn’t take a charge.  I’ve heard rumors that Shimano released a batch of bad batteries at some point; I thought they were all out of the system by now, but who knows.  My brother has replaced the battery and now seems to be getting performance similar to mine.  Certainly an annoying chapter in his Di2 experience, but hardly an indictment of Di2.  As with any part of a system, batteries can fail, but Shimano has proven they can produce batteries that work reliably over time.  I just might avoid installing a brand new battery right before a tour.  And compared with the Alfine disaster, at least I know what failed, and in a general sense why.  Who knows what failed on my hub, because Shimano isn’t talking.  Further, the Di2 fix was easy and relatively inexpensive.  Preventive measures with Di2 are also easy—carry a spare battery on tour.  Try that with an Alfine hub.

The problem that had me most concerned about Di2 was unreliable shifting, far worse than the SRAM X9 derailleur it replaced.  Spurious shifting, really—it would change gears without any input from me.  I played with the derailleur offset, thinking it might be out of alignment, but that just caused slow, spurious shifts.  I eventually changed the offset back to –4, which is what the Shimano calibration steps result in on my trike, but the spurious shifts continued.

The crazy-long chain is perhaps the Achilles heel of recumbents, a situation I lament in my post about recumbent belt drive.  In certain conditions it represents a large swinging mass that can wreak havoc on the drivetrain.  Trike designers deal with this problem in different ways; ICE’s is to dampen the movement with chain tubes.   Under power/load, the drive side of the chain isn’t an issue because it’s under tension, but the return side is a slack, swinging sack o’ potatoes.   ICE managed this on my Q by pulling the return line up near the frame with a short piece of fabric that hung off one of the derailleur cable stays.  The fabric looped around the chain tube.  Simple and effective.  But in the transition to the Franken-trike I call the HDQ, where the old, broken Q cruciform was replaced with an Adventure HD cruciform, the geometry was different and I couldn’t use that piece of fabric.  I simply omitted it and never looked back, until Di2.

Apparently the Di2 derailleur is much more sensitive to side-to-side movement than the conventional derailleur it replaced.  Suspecting this might be the problem, I installed part of a TerraCycle return idler.   The idea is to put a second idler between the front idler and the rear derailleur, to keep the chain from bouncing around so much.  However on my HDQ, I couldn’t figure out a position for the idler that didn’t interfere with the drive side of the chain.  So I removed the idler and installed just the idler axle, essentially a horizontal metal bar.  Then I looped the return chain (inside the chain tube) over the top of the axle bar, and used a zip tie to prevent the chain from sliding off the end of the bar.  This allows the chain to move side-to-side, following the position of the rear derailleur, but significantly reduces the amount of unintended sideways bouncing.  And I haven’t had a bad shift in the eight months since.

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Idler Interference

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Interference Resolved

Complete disclosure:  At the time I was messing with all of this, I noticed that I’d never bothered to re-adjust my rear suspension after a massively loaded self-supported tour back in 2012.  That was, ahem, almost three years prior.  Carrying about 200 pounds of gear required a much stiffer suspension to keep the power side of the chain aligned with the center point of the suspension pivot, per ICE’s instructions.  Since the tour I’d been running with the suspension adjusted far from optimally, which may have caused some “pogo-ing” when pedaling hard.  So I fixed this at the same time I added the rear idler thingy.  And it’s possible that this, not the idler, solved my problem.  I don’t think so, but either way the problem is solved.  And managing that massive return chain line is always a good thing.

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Suspension Properly Adjusted

All’s well that ends well.  The initial problems I had with Di2 are completely resolved, and the biggest wasn’t a Di2 issue to begin with.  What remains is the most significant improvement in my ride since getting ‘bent.

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2 thoughts on “A Year of Di2

  1. Jose Vidal

    Very interesting . I have a question about my new Alfine Di2 battery and Li-On 7.4V DIY I built myself. I have all the original system Shimano, except SM-JC41 and SM-BTR2, who manufactures these myself, but for some reason the system does not work. Any ideas? Thank you.

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    1. Kurt Post author

      Jose, have you tried connecting the E-tube software and seeing if it recognizes all the DI2 components? It’s possible you have components running incompatible firmware versions, though I’ve never seen that myself. I noticed in one of the you-tube videos demonstrating making a DIY battery that he never talks about setting up the system. It might be that his battery worked because he’d already done that step. I suppose it’s possible that the setup won’t work without a bona-fide Shimano battery, but I don’t know how the system would distinguish it from the DIY battery. At one point I thought the battery unit actually contained a microcontroller, but apparently not according to the video. Maybe over the winter I’ll tear one down and see for myself what’s inside.

      And an obvious point: Do a continuity test of your DIY SM-JC41 connectors.

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