@Hochprofil: which big frame do you think looks good?

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No longer in the industry

BIG bike! Looks good. Enjoy it.

All i can say is WOW ! A very very BEAUTIFUL BIKE ! ENJOY IT.

It's inside the massive headtube!... only joking, it's in the seatpost.

Here are some photos of the build and my hack job with the battery.

LOL Not sure I see what you did there.
Why strip the battery, then wrap it in tape? What's that do?

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I only train on days that end with "y".

Eli

Serious question?...

1. Physical dimension - casing adds about 5mm around the edge and would never fit within the post

2. Connectivity - see attached

Cool...I haven't been around long enough to see those. Maybe do that on my Caad10 (take it from under the bb), but then I'll have to get inside the bike and change the wiring, right? How do you pull the wiring up through the seat-tube? Also, how small is the battery? Small enough to fit in 27.2 or no way? The second picture makes it look like...maybe! My battery looks like no way (Ultegra).

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I only train on days that end with "y".

Eli

Yeah, it's heaps cleaner and makes sense to go internal. The battery charge lasts for a very long time. I actually got the Ultegra electronics kit as it had superior cabling at the time, but the battery is the same for DA.

Battery size shouldn't be an issue as you can separate the two cells (about AA in size), solder together and create a tube shaped unit for standard posts.

If you have a standard Di2 fit out, all you need to do is route the battery cable up inside through the seat tube. I used a piece of steel wire with a bent hook to grab the cable from inside the BB area. If your stock cable isn't long enough, you can order different lengths from a Shimano dealer. Just measure your seat tube and allow a bit of slack for connecting / disconnecting with the post removed. You will see that I actually took the socket from the stock battery holder and the socket from the base of the battery housing and they are connected together within the seat tube. This is important as the Ultegra unit has small circuitboards inside these parts which are required for the whole system to function so they must be retained. Secondly, they allow for easy charging as you can place the socket part from the original battery case into the Shimano charge unit to charge - without having to remove the battery from inside the seatpost.

You will need to be careful not to short the battery or even worse connect with wrong polarity as you can blow not only the battery - but the whole DI2 circuit (circuitry in the derailleurs I believe). Not for the feint hearted! I can try and post a guide if I get time.

Otherwise, wait a couple of month for Shimano to release the Di2 internal battery (tubular shaped designed for seat post installation) - part no SM-BTR2. Exactly the same as above but will probably sting you about $150 USD though.

Fascinating. When/if you find time to post a guide, please shoot me a PM and let me know? I'd love to try this (read: have my buddy Mike try this, who is heaps more handy than I am).

Cheers

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I only train on days that end with "y".

Eli

Hi everyone,

I'm writtig to you regarding the Di2 modifications. In fact I'm working in developping a e-bike test platform
that will use the gear shifting system Shimano Di2 6870 and we want to replace the battery (external SM-SMBTR1) for a voltage source but we are not sure about how to connect the three conctacts and the polarity.
Have you measure the voltage output of three battery pins?

Thank you in advance for your help.

Ricardo

You don't need all 3 wires. You only need the + and -. Probably black and red.
Also, you don't need that little circuit board either. You only need the chip from the battery mount that has the 2 posts on it. See the picture where he has is hanging out of the top of the seat tube. That part you need.