cthenn

I've had my Di2 system for over a year(?) now, and generally, everything works well. But I've had a problem on more than one occasion where the battery will drain after working on my bike. When I'm just doing a lube refresh, what I do is just flip the bike over, wipe the chain down, and re-lube. I always shift into the big ring and little cog to do this. So, after flipping the bike over, I'll turn the cranks, and shift into this gear combo. After finishing, I'll just flip the bike over, and leave it in that gear combo. But it seems like every time I do this, the battery will drain out before the next ride. Usually I'm lubing the chain after a ride, or well before I go out again, so I'm not immediately jumping on the bike afterwards. I can alleviate this problem by simply shifting a few gears on the bike before putting it away. Not sure what I'm doing to drain the battery, has anyone ever experienced this problem?

Metaluna

Hmm, this is a longshot, but maybe one of the "shoulder" buttons is getting stuck in the down position when you flip the bike over, and that's causing the system to stay active and run the battery down? I'm talking about the buttons on the newer Di2 levers that are hidden under the hoods, sort of on the knobby part above the brake pivot.

faulker479

Others that have had this problem fixed it by loosening the derailleur limits screws. The rear derailleur may be trying to shift further than the High Limit screw is allowing. Try unscrewing it until you can see a gap, screw it back in where it just touches the derailleur and then unscrew it a full turn.

TimothyH

Always do the easy and cheap thing first.

Forget about B screws and limit screws for now.

Hold the bike in the air using the saddle and spin the cranks a few times after flipping the bike back over. If it shifts into a different gear then that's your problem.

I'll bet the Di2 lever has been pressed when it is flipped and the bike is trying to shift into the next gear.

Steve B.

This. Beceause the shift never completed, the derailer is still trying to complete the shift, the motor is still pushing and the battery gets drained.

As a PSA about using Di2, always make sure nothing is causing the shift buttons to be pressed if you transport the bike on its side in the back of a car.

noglider 

Elevators turn their own door motors off when the door fails to close. This would be a good place for that kind of logic.

Seattle Forrest

Never occurred to me. Thanks! I don't usually bring the charging cable when I travel with my bike, it would be very disappointing to arrive with a single speed.

faulker479

He said "I can alleviate this problem by simply shifting a few gears on the bike before putting it away" It may be that a shift button is inadvertently being pushed when he flips it back over, but the problem is only while in large chainring an smallest tooth cassette cog. So yes spinning the cranks is the best way to tell if a button was pushed, but having a High Limit screw that is too tight seems to be the real issue. Never mentioned the B screw.

Seattle Forrest

The rest of the post was good advice specific to this problem, but this is a really good principal in general.

Koyote

Hmm. On my Di2 bike, hitting a button while NOT pedaling will indeed move the derailleur, just like on a mechanical system. So I'm not sure that this is the issue. But I sure would like to see the OP come back to tell us if this did work.

'Course, no one suggested another obvious solution: buy a workstand and service your bike right-side up.

Metaluna

I think the issue is that when you don't pedal, the derailleur gets jammed by the chain so it ends up stuck between gears and continuously drawing power (which is not only bad for the battery but must be terrible for the stepper motor and various mechanical bits like pivots). Pedaling allows the chain to shift, both clearing the jam and indicating that the RD was stuck in a bad state. I suspect that there's enough slop in most chains that you could get away with one shift on the RD, but if a button is stuck it will try to do multiple shifts until it jams.

ChinookTx

Even on a work stand, he could hit the button when installing the bike on/taking it off the stand.

After reading this thread, I checked my bike because I've had this issue occasionally. Sure enough, the limit screw was just a bit too tight, and I could semi reliably make the shifting go up to the largest cog but not "give up trying", as if it thought it wasn't fully there yet.

Only time will tell if this fixed it, but after seeing the behavior, I'm pretty sure it will.

Koyote

Thanks, that does sound plausible -- especially since, as I understand it, a Di2 RD will actually overshift and then come back to the correct gear, in order to accomplish an actual shift more rapidly.

jadocs

I agree, first thing that jumped in my mid as well.

rm -rf

I can shift a couple of clicks without spinning the crank -- I don't think it's straining the motor, the chain is just at an angle.

The limit screw sounds like the problem. It needs a gap to allow an over shift. The low limit (largest cog) is adjusted without extra clearance.

I could see this draining the battery overnight. If so, riding in the smallest cog would drain it too!

OP, do you ever leave it in the smallest cog after a ride (without flipping the bike over)?

(Or perhaps the hidden top of the hood buttons? but they aren't running the motors.)

From the dealer manual DM-UL0001-02.pdf

Shift the rear derailleur to the smallest
sprocket, and then tighten the top-side
stopper adjustment bolt until it touches
the stopper at the position where the
rear derailleur finally stopped. From this
position, turn the top adjustment bolt
counterclockwise one turn so that an
over-stroke allowance can always be
maintained.

~~~

The largest cog is adjusted closer:

Shift the rear derailleur to the largest
sprocket, and then tighten the low
adjustment bolt until it touches against
the stopper.
If it is tightened too much, the motor
will detect a problem and gear shifting
operation will not be carried out
correctly.