Shimano Di2 shift not responding fail to startup sleeping

Symptoms of Di2 DN110 battery problems
Pressing shift doesn't do anything, pressing it several times wakes the system up. Like its sleeping.

Pressing the shift mode button on the (SHIMANO XTR SC-M9051 Di2) display always works even when shifters don't respond. Battery shows full.

Once its 'woken up' it shifts normally.

Gets slightly worse if not fully charged.

Symptoms of DN110 Di2 battery failing more
Have to press the shifters dozens of times to wake it up. (Seems worse when its warm in afternoon than when colder in morning?)

Pressing the shift mode button on the (SHIMANO XTR SC-M9051 Di2) display always works even when shifters don't respond. Battery shows full.

Once its awake, shifts ok but after not shifting for a minute, it needs waking up again with a single press before it then starts shifting again.

Fully charging before use makes it fractionally better.

=Checking the battery=

I took mine apart (Details below) and found both cells seemed to be outputting 4.1v and were perfectly ok. I charged them externally with a Li-Ion balance charger and seemed ok too. I tried some other random 18650's I had laying around and they exhibited same shift problems as above. I was starting to doubt there was a problem with the batteries now.....

Perhaps the voltage drops immediately under load, but I imagined the load pressing a shifter button was a pretty minimal current draw. Strange....

=To fix the battery=

Anyway I took the plunge and bought a couple of replacement cells, they are 3/4 AA size, aka 14430 LiIon (14mm diameter, 43 mm long)

(eBay listing title = Replacement Battery ICR14430NR For ICR14430 WITH SOLDER TABS 2pcs/pack) £12.16 + £2 shipping

Note you need non-protected cells to fit lengthways and tabs on unless you have >80W soldering iron or access to a spot welder.

Remove DN100 Di2 battery end
There are two tabs that appear to hold the end on - don't try and lever them up, you just need to pull and wiggle the end and it will come free, most of the force holding it in is the rubber O-ring seal, not the tabs. Once free carefully keep pulling, the batteries will come out like a sausage, expect a reasonable amount of resistance.





Once apart remove the 3 solder tabs on the board being careful not to short them.

(Don't try and shortcut this by leaving them and just removing battery connections, I did this and all it does is make it much harder to put back)

Remove all the tape holding it all together carefully, you can re-use this as its a good thickness for a snug fit.

Then remove the connections on each end of the battery, then unfold the batteries to remove middle connection.

Soldering thee new Di2 batteries back
This is the difficult bit. I had a lot of f*cking about with this.

The tabs on the original batteries are all in the right place, the ones I got had the tabs on the +/- facing opposite ways which is not good. The originals are in near enough a straight line, if you get batteries with tabs facing same way this would make life a lot easier.

Start by working out how to join the middle of the batteries, it needs to be enough so you can solder one tab onto the other but not so much the fold sticks out proud of the battery.

The largest problem is the membrane is only just long enough to solder where the original tabs are - and it wont stretch, and making it so it remains under tension when you are finished will make the joints probably fail in the long run.

You can use pliers to flatten the membrane battery connectors out as they are shaped like a little connectors to slide over the original tabs to make a nice connection.



Original batteries showing original extra tabs that perfectly fit the membrane connectors - in hindsight I may have tried to remove these and re-spot weld them onto new batteries



Afraid this is hard to describe I should have take some pics....

Basically I ended up with a compromise, so middle connection first - joined to -'ive on first battery, just on the edge of the tab. Very difficult as heat wicks out quick (I had 80W Weller). Next to the +ive, this should just sit on the edge of the tab. I used Kapton tape to hold the membrane in place. Finally the end -'ive, again just on the edge of a bit of the tab. Use original tape to tape it up as you go to hold the ensemble together.

Then its fairly easy to solder the 3 contacts back on the board, you may need to straighten them, don't short them with pliers like I did.

After testing I put conformal coating on the pcb, sparingly greased the silicon o-ring and slid the sausage back in.

System back up
I dont know if this is normal but plugging battery back into my bike does nothing, I have to attach the charge lead to magic it back into life, not sure if this is normal I cannot remember how it was when I first built it all?

Anyway I now have a fully function bike again, instant gearchange on first pressing!!!

Useful Notes
I didn't dare test it on a bench power supply as the middle wire (presumably balance charge wire) being unconnected may have some effect - I didn't want to risk blowing anything up - I thought safer to try new batteries first.

The XTR SC-M9051 battery meter (I think) only measures voltage and is useless at telling you if that batteries are any good.

Due to difficulty of reattaching that membrane and higher cost of the 14430 cells, in hindsight I maybe have just used 2 x 16340 cells (or something similar), wire, and heatshrinked it all back together.

Don't buy 'cheap' unbranded or fake branded cells, they are always useless immediately or shortly thereafter, always.

If you have access to a spot welder (I would have at least tried this in hindsight) I would suggest removing the original battery spot welded connectors, bought tag free batteries and spot welded connectors back to new batteries in EXACTLY the same places and it would have been dead easy to put back together.

I hope this helps someone, sorry I have thrown it rather incomprehensibly together.