Ultegra Di2 hacking

Discuss light weight issues concerning road bikes & parts.
drmutley
Posts: 344
Joined: Fri Feb 11, 2011 4:23 am

by drmutley

Nimra:
It's easy just to cut the mount down to a very small size and stuff it down the seatpost, then connect a lipo stick battery terminal side...

Nimra
Posts: 6
Joined: Mon Apr 15, 2013 7:25 am

by Nimra

Hi,
yo ... thanks. I guess this is the way I have to make it.
I mentioned, that Calfee do the same ...

by Weenie


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rmerka
Posts: 618
Joined: Wed Mar 06, 2013 4:23 pm
Location: Austin, TX

by rmerka

Super_fast wrote:
jeffr wrote:In di2 there is no single 'cpu' or 'brain'. It's a distributed networked system with some processing capability at each point. Just like a bunch of computers on a LAN. They each tell the others what they are doing and broadcast commands and status. I suspect ui2 is the same.


Exactly, in every part in the Ultegra DI2 group is a micro-controller so it can communicate with the other parts. The current Dura Ace shifters have no electronics in them, but the Ultegra shifter do have a small board with a micro-controller.

I posted on Fairwheelbikes some results of my measurements.


If anyone's interested this is what Shimano uses: http://en.wikipedia.org/wiki/CAN_bus which is exactly what jeffr and Super_fast are saying.

Super_fast
Posts: 341
Joined: Tue Nov 01, 2005 9:36 am

by Super_fast

A sales rep from Shimano mentioned 1 time the system uses CANbus, but I have never seen any proof.

CANbus uses 4 wires, DI2 only 2 since the information is modulated on top of the supply line. This modulation is certainly not an (open) standard. The microcontrollers used by Shimano seem to me made on special order, contrary to the old Dura Ace that used Ti MSP430 micro controllers.

maxxevv
Posts: 1952
Joined: Wed Feb 09, 2005 4:51 am

by maxxevv

Super_fast wrote:
CANbus uses 4 wires, DI2 only 2 since the information is modulated on top of the supply line. This modulation is certainly not an (open) standard.


That's not quite true. CANBus can utilize 2 wires (last paragraph) :

http://www.axiomatic.com/whatiscan.pdf" onclick="window.open(this.href);return false;

Its a 'half-duplex' as Fluke puts it here:

http://www.fluke.com/fluke/usen/solutio ... CANBus.htm

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rmerka
Posts: 618
Joined: Wed Mar 06, 2013 4:23 pm
Location: Austin, TX

by rmerka

I was reasonably sure that Shimano was using either the ISO 11898.2 or 11898.3, both a 2-wire CANbus standard, but I don't work for Shimano so I can't say with absolute certainty. But that is still my best guess. It makes sense to me that they would choose the CANbus protocol as it's proven with regard to reliability and quite popular in the auto world.

Nimra
Posts: 6
Joined: Mon Apr 15, 2013 7:25 am

by Nimra

drmutley wrote:Nimra:
It's easy just to cut the mount down to a very small size and stuff it down the seatpost, then connect a lipo stick battery terminal side...


Hi,

it's me again ;-)

What tools are useful for cutting the mount down? Could it be opened partially by disassembling?
Or do I need a Dremel do grind the thing down?

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rmerka
Posts: 618
Joined: Wed Mar 06, 2013 4:23 pm
Location: Austin, TX

by rmerka

Nimra wrote:Hi,

it's me again ;-)

What tools are useful for cutting the mount down? Could it be opened partially by disassembling?
Or do I need a Dremel do grind the thing down?


I'm curious why, at this point in time, you would cut down the external Di2 battery in order to fit it in a seatpost. I mean no disrespect to the DIY attitude as I have GREAT respect for it. It's just that a year ago this made perfect sense, but now you can just get an SM-BTR2 and stick it in there. For probably less money than buying a quality lipo battery and a mount...

Nimra
Posts: 6
Joined: Mon Apr 15, 2013 7:25 am

by Nimra

Hi, the sm btr stick don't fit into my aero seatpost, an capacity is pretty low.

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rmerka
Posts: 618
Joined: Wed Mar 06, 2013 4:23 pm
Location: Austin, TX

by rmerka

Nimra wrote:Hi, the sm btr stick don't fit into my aero seatpost, an capacity is pretty low.


Makes sense now from a fitment standpoint. Capacity wise, from my experience, you don't need a lot for di2. Good luck and stay safe. As a side note make sure you use top quality lipo batteries so this doesn't happen to your backside:

Image

Dammit
Posts: 443
Joined: Sun Mar 27, 2011 8:16 pm

by Dammit

rmerka wrote:
Nimra wrote:Hi,

it's me again ;-)

What tools are useful for cutting the mount down? Could it be opened partially by disassembling?
Or do I need a Dremel do grind the thing down?


I'm curious why, at this point in time, you would cut down the external Di2 battery in order to fit it in a seatpost. I mean no disrespect to the DIY attitude as I have GREAT respect for it. It's just that a year ago this made perfect sense, but now you can just get an SM-BTR2 and stick it in there. For probably less money than buying a quality lipo battery and a mount...


I can (and have) make an in-seatpost battery for my 7970 for less than 10 euro.

brownish
Posts: 98
Joined: Thu May 03, 2007 5:47 am

by brownish

I need an EW-SD50 wire longer than the longest available 1200mm. Has anyone been able to successfully cut and splice two together?

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rmerka
Posts: 618
Joined: Wed Mar 06, 2013 4:23 pm
Location: Austin, TX

by rmerka

I wonder if you could use another internal junction box? Has anyone ever tried that?

Nimra
Posts: 6
Joined: Mon Apr 15, 2013 7:25 am

by Nimra

rmerka wrote:I wonder if you could use another internal junction box? Has anyone ever tried that?


... me too. But I think you need one of the battery connectors (seat tube type or frame type).

There should be no problem with longer cables (soldered or crimped) if they don't get extreme longer.


So ... LiPo batteries are dangerous ... all of them. You need a very good charger / balancer and you should take care for the right settings.

LiFePo batteries are way safer (we use them in motorcycles for the track), they can even get charged with standard equipment.

by Weenie


Nimra
Posts: 6
Joined: Mon Apr 15, 2013 7:25 am

by Nimra

This picture shows the electronics of a SM BTR1 seatpost battery.

Image

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