DURA-ACE R9250 semi-wireless Rear Derailleur Manual published

Updated August 4, 2021 by BetterShifting Terry

Half a year ago Shimano submitted their R9250 rear derailleur to the FCC for approval. This FCC filing is required because of the wireless (BluetoothLE/ANT) technology in the new semi-wireless 12 speed Di2 groupsets. Back then there wasn't a whole lot we could tell from the documents, other than this:

  • It's called R9250
  • It uses the BT-DN300 battery
  • It therefore also uses the EW-SD300 wires
  • It's semi-wireless, both derailleurs are connected to the battery

Part of the FCC documents is also the manual for the rear derailleur itself.

Unfortunately Shimano requested that to be private/confidential, so we couldn't see it.

Until today. FCC documents can only be confidential for so long, and today the 6 month period ended.

What can we learn from the manual?

Let's walk through the manual and see what we can find. You can actually download the manual on any FCC related website, but I've also uploaded it to bettershifting.com for your convenience: R9250 Rear Derailleur / Battery charger manual.

If you want to skip ahead to the most interesting sections of this page, here are some links:


Interesting! It looks like the charging port has moved from the Junction A to the rear derailleur. Not only that, but the rear derailleur now also features an LED and a button mode switch.


No more junctions boxes! No wires up front

Since the new system will be semi-wireless - the derailleurs are connected to the battery via EW-SD300 and that's all - it makes sense for the rear derailleur to have all these things. The entire Junction A will no longer be needed, reducing clutter and wiring at the front of the bike.

Also, a patent previously filed by Shimano suggests that the battery will have an integrated B Junction. The battery in the image below has three ports, two of which would be EW-SD300 ports. The third port is most likely not an EW-SD300 type and used for sensors, lights, etc.

Two ports on the new Di2 battery

What will you do with extra components like satellite shifters or climbing shifters? It looks like you'll be able to plug those in at the Shift levers - they'll have 1-2 EW-SD300 ports and one satellite shifter port. More on that at the bottom of this page.

Synchroshift and Wireless function

So what does the button do? Quite a lot actually. Look at this image:


That right, it:

  • Lets you check the battery level
  • Changes shift mode
  • Enables BluetoothLE connection mode
  • Switches to (micro)adjust mode
  • Is used to pair switches

Missing from the list above is RD Crash Reset mode. This is either a mistake.. or the functionality has moved to the E-Tube Mobile app. The latter makes sense, as the button now suddenly has a lot of functionality tied to it.

And yeah, Synchronized Shift still exists:


Battery status

The battery status LED works just like before, indicating the charge level of the BT-DN300 battery:


However, looking at the About wireless functions section of the manual, this particular bit is interesting:


Dual control lever battery level information

Previously, users on WeightWeenies have suggested that the shift levers would be self-charging and not require any batteries to operate. If so, there would be no need for battery level data to be sent over ANT or BluetoothLE. I haven't actually seen the new levers myself, so I'm just guessing here. Your guess is as good as mine :).

Charging the battery via the rear derailleur

So yeah, you'll charge your 12 speed Di2 battery via the rear derailleur. The charging cable looks a lot like Shimano's power meter charging cable. It's not 100% the same though, there are subtle differences.


Either way, this new charger will certainly be a lot less fiddly than the current SM-BCR2 charger and the other end just plugs into a USB port. No more charging brick!


This is what the prototype unit looks like from the outside:

RD-R9250 outside

You can see the charging port at the bottom and the EW-SD300 Electric Wire port on the top.

The inside of the unit looks like this:

RD-R9250 inside

The red arrows are Shimano's, but I added the letters myself. This is what they indicate:

  • A: Antenna
  • B: BluetoothLE / ANT module
  • C: Charging port
  • W: Wireless integrated Circuitry

Note that the circuit board has RD-R9250 printed on it.

Also, take a good look at the part of the circuit board the EW-SD300 wire plugs into. Because the same part can be found on the circuit board for the ST-R9270 Hydraulic Disc Dual Control Lever:

ST-R9270 inside PCB

Not one, but three of them! Now.. as with previous generation hydraulic dual control levers, you probably will not be able to connect three wires to it - current generation levers feature two E-Tube ports (EW-SD50 type). However, two ports just like the current levers seems reasonable.

User ooo from WeightWeenies suggests that it's 1 EW-SD300 port + 1 satellite port for the hydraulic levers and 2 EW-SD300 ports + 1 satellite port for the rim brake levers.

The size of the unit pictured above is 16.6 mm x 23.5 mm, by the way:

ST-R9270 PCB drawing


When will it actually be released or even announced? No one outside of Shimano really knows. I'll be there to keep you up to date when it happens though!

September seems likely, but I'm just making an educated guess here.

BetterShifting Terry

About the Author - BetterShifting Terry

I enjoy playing with bike tech - both bike building and wheel building, bike maintenance and of course, Di2. Besides writing content and working on the technical side of BetterShifting, I also work as a Software Developer in The Netherlands. Read more on the About this site page.

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