Di2 woes, and a couple of questions

[pclay]

Hi

For the past year or so, the battery on my Ultegra Di2 bike has been going from fully charged to flat in the space of about 4 days. Riding the bike just meant I had to charge the battey the day before the ride. The bike has done 5000 miles and the groupset is Ultegra 6770 6870 from 2016.

I got fed up of the battery draining, so I bought a new battery, upgrading from the SM-BTR2 to the newer BT-DN110. Yes, syncro shifting is now possible.

But alas, the new battery went flat in 4 days. I took the bike to my a LBS who ran a Di2 diagnostic / battery drain check on each compoinent. They have flagged the rear derailleur as being the issue.

I have unplugged the rear derailleur, and 4 days later the battery still has charge.

So, I have 2 questions really:

1 Will the Di2 rear derailleur R8050 work with 6770 6870 shifters and front derailleur? (I think it will)

2. If my old 6770 6870 derailiuer is the issue, is it good for the skip, or can any kind of reapir be undertaken?

Thanks

 

[si_c]

In terms of compatibility, this is the go-to website but it seems the newer 11 speed stuff is not compatible with the 6770 derailleurs.

It sounds like there is an issue in the derailleur causing the battery drain, it might be fixable by someone who understands electronics, but your best bet for a replacement derailleur is probably ebay at this point.

 

[tom73]

paging @JhnBssll

 

[JhnBssll]

You can't mix 10 speed and 11 speed mechs but the shifters would be fine so to use an 11 speed rear mech with the 6770 shifters you'll need a new front mech from an 11 speed di2 group - ie 6780 onwards.

 

[pclay]

Correction. My bike has 6870 11 speed Di2.

 

[JhnBssll]

In which case no problem at all, an 8050 mech will work just fine

 

[pclay]

Thank you

They are expensive items of kit! My bike has been in the shed since Tuesday afternoon with the RD unplugged (3 days). The battery is still charged! If the battery is still charged on Sunday (5 days of RD being unplugged) then I will order the 8050 RD.

 

[pclay]

The RD i have is the 6870 GS (medium cage) as my cassette goes upto 32t.

Would the short cage 6870 work with this cassette, perhaps with a wolf tooth extender or similar? The only reason why I ask is because there are many more second hand SS 6870 RD on ebay than there are GS.

I have another bike with 105 short cage working with a 34t casette with an RD hanger extender.

 

[derrick]

The RD i have is the 6870 GS (medium cage) as my cassette goes upto 32t.

Would the short cage 6870 work with this cassette, perhaps with a wolf tooth extender or similar? The only reason why I ask is because there are many more second hand SS 6870 RD on ebay than there are GS.

I have another bike with 105 short cage working with a 34t casette with an RD hanger extender.

Just change the cage. https://www.sjscycles.co.uk/search/?term=di2 rear derailier spares

 

[JhnBssll]

Worth noting that the short and long cages on the R8050 are not interchangeable without modifying the end stop position. I dont know if this is a new thing for the latest Ultegra or if it also affects other models but I found out first hand to my chagrin when the ceramicspeed cage didn't fit my R8050 GS mech. I had to buy an SS mech and sell the medium cage one on.