HI ,
i'm looking to buy a R8050 Di2 groupset , my frame don't have any kind of internal mounting , so only option is to go with external battery "SM-BTR1" and external battery mount "BM-DN100" , i'm buying SM-EW90 Junction A with the group .
Now , i'm curious about 2 points :
1- As per my understanding , BM-DN100 is enough for the syncro-shifting to work , even if i'm working with older model external battery "SM-BTR1" Am i correct ??
https://carltonbale.com/shimano-di2-e...omment-page-8/

2 - I'm not buying the wireless unit , i'm looking to the ability of customizing my group via e-tube pc app ... Can i use SM-BCR2 charger with the "BT-DN100+SM-BTR1+SM-EW90 Setup" for charging battery through Junction A and connecting group to PC ?
R8050 manual shows SM-BTR1 is to be used with SM-BCR1 , However , e-tube compatibility guide shows that BM-DN100 is compatible with SM-BCR2 ..

Please advise

I don't think that will work. Pretty sure there's smarts in the new battery that control the system.

You mean which part will not work , the syncro shifting or charging SM-BTR1 using SM-BCR2 through junction A "SM-EW90" ??
As per : Shimano Ultegra and Dura-Ace Di2 Electronic Shifting ? Everything You Need to Know ? Carlton Bale .com
BM-DN100 is responsible for syncro shifting and connecting to wireless unit "if i understand correctly BM-DN100 have smarts that control the system"

What frame are you using that you cannot put the battery inside the seatpost? No bike comes with an internal "battery mount", you just put a battery plug adapter in the seatpost and call it a day.

I believe your DN100 scheme will permit synchro shifting per the latest compatibility chart...

https://e-tubeproject.shimano.com/pdf....3.3-00-EN.pdf

Frame is a scott Contessa speedster , problem is to route the battery cable to the battery inside the seat post ..

Doesn't look like it would be that much of a problem, not moreso than any other bike not-sold-Di2. Seeing photos of the bottom bracket cluster and where/how cables come out of the frame would help.

Frame don't have internal mounting to guide the cable from junction B to battery inserted inside seat-post

From Compatibility Guide is think syncro-shift is enabled , From R8050 Guide BM-DN100 is compaible with SM-BCR2 for PC Link .
Question is will SM-BCR2 work for charging through Junction A ? As Group manual , shows SM-BCR2 is only used for SM-BTR2
https://si.shimano.com/pdfs/dm/DM-R8050-02-ENG.pdf

No metal frame has such a "guide". My Carver didn't.

https://imgur.com/a/sFfTf

Only question is whether the bottom bracket you use allows a cable to go around it.

Shimano BBR60 .

Shimano BBs like that should be fine for internal Di2 routing aroun d the center sleeve. Only remaining question is how cables exit the frame to reach the FD and RD.

Not having seen this frame, I doubt you need to worry about external batteries....unless you really like the added complication/clutter. But like I've said, I haven't seen anything other than Scott's website photos to judge by.

The external battery isn't necessarily your only option. Alternatively, Shimano sells an external holder for the internal battery, the SM-BTC1. So you could buy an SM-BTC1, a BT-DN110 internal seatpost battery, and an SM-BCR2 charger. Now you have a system that mounts externally, works for both charging and wired firmware upgrades, AND could be moved to an internal seatpost setup in the future without changing out any hardware (except cables).

That said, I used to have the exact external battery/DN100/R8050 setup you are looking at, and it definitely worked perfectly with synchro shift. I had a wireless unit in the system but I don't think that matters.

As for "e-tube" compatibility, they are possibly talking about compatibility with the e-tube Windows app over a USB connection. On internal battery systems, the SM-BCR2 charger can also be used for limited diagnostics and firmware upgrades, so maybe that works for external battery systems as well? I don't know if the SM-BCR2 can actually charge the external battery though. I've Googled this and couldn't find any conclusive first-hand reports of success or failure. If it does work, I would recommend getting that instead of the normal external charger, for the connectivity checking and firmware upgrade capability.

Thanks for the reply .
i'm buying the SM-BCR2 as syncro may not work if all component aren't updated to same recent FW i assume also i need it for customization "shift speed , etc .. "
i can buy an external charger SM-BCR1 "Only if BCR2 don't work for charging" , SM-BTC1 is almost same value
So Question is , SM-BTC1 is intended for Mountain DI2 , and it have 6 ports as i understand and can be used instead of junction B , but is is compatible with rest of the group ,,, can't find that in compatibility matrix , not sure if someone have done that before

I didn't even realize that the SM-BTC1 had a B junction in it. I thought it was basically just a plastic tube to hold the battery, but if it also replaces that horrible under-BB junction box (SM-JC40), then it's starting to look like a pretty good value (it looks like it might even include an e-tube wire for the battery, so that's another $20 savings). Anyway I'd be amazed if it didn't work with road groups, as I think the B junction just passively wires all the ports together and doesn't care what kind of packets are being sent over the CAN bus. The other junction B's (SM-JC40, JC41) are used for both mountain and road, so this should work with both also.

P.S. According to this, the SM-BTC1 is compatible with road and mountain groups. It doesn't specifically list the Ultegra 8000 generation, but from an e-tube point of view, there's no difference.

https://www.bike-discount.de/en/buy/...sm-btc1-220699

well , vice versa , in the M8050 guide , you can use sm-btc1+ BT-DN110 with no Junction or BM-DN100 + BTR1 + SM-JC40 ..
I believe it may work , not sure why sm-btc1 is not mentioned in R8050 guide "weight maybe" ... cable routing looks worse though in sm-btc1 case