Di2 Noob with questions

[Epicus07]

Hey Folks,

My new ride has GRX Di2 with a seatpost mounted ?battery. If I were to get a seatpost that wasn’t compatible with battery storage, where might I put the battery ?

Also how is this all connected? It’s a 2x system with a charging port in the handlebar end and what I believe is a battery in the seatpost. Is there a junction box somewhere internal ?

[Tim Porter]

An incredibly smart and generous guy named Terry has a Shimano oriented site that most likely has answers to all your questions about Di2. Very helpful--send him a coffee in recompense. [No commercial relation, btw.]

https://bettershifting.com

[gravelreformist]

bettershifting.com has a ton of good information. This page might be helpful to start. https://bettershifting.com/building-...hs-and-wiring/

Are you looking to install a dropper post or just a different standard post? Some frames have other locations available, but we'd need to know more specifics about the bike and what you're looking to change.

Also hard to say exactly how yours is wired since basically it works any way that all the wires are connected together. Generally the shifters are wired to the bar end junction, and the junction or a shifter is wired to an internal junction somewhere in the frame, which then goes to the battery and derailleurs.

[Epicus07]

That looks like a great resource thanks

[joeminglin]

Depends on the frame. My Ibis hakka has a compartment cover on the DT by the BB that has a mount for a battery.

Doesn't campy use an internal battery mount that uses the water bottle cage bolts?

[weisan]

Originally Posted by Tim Porter

An incredibly smart and generous guy named Terry has a Shimano oriented site that most likely has answers to all your questions about Di2. Very helpful--send him a coffee in recompense. [No commercial relation, btw.]

https://bettershifting.com

I agreed.
And he's among us in this community. His handle is TerryDi2. You could PM him.

[TerryDi2]

Thanks guys!

So... yeah..

There are Di2 'compatible' seat posts, which basically means you can install the battery in those seat posts using the clips and bits Shimano supplies with the battery.

There are plenty of 'not compatible' seat posts, but that doesn't mean you cannot install the battery in one of those - you generally just need a seat post battery holder. One that is the right diameter for your seat post :).

I have used PRO, Deda & Ritchey battery holders/adapters in the past. I think the Deda is my favourite, but it doesn't really matter... they all do the job.

Now... on some bikes you really cannot put the battery in the seat post. Canyon usually puts the battery in the down tube, because of their fancy seat post design. This is a pain, because sometimes you need to get to the battery (if something goes wrong with the Di2 system).
Having to remove the crankset/BB just to get to the battery isn't great. Some bikes have covers on the bottom of the down tube that lead to a battery compartment.. those are better :)

On my Di2 MTB I put the battery in the steerer - because I could :).
My MTB had a dropper post, which wasn't hollow and there was no space for the battery. Putting the battery in the steerer works, but the ideal place is still the seat post.
(https://bettershifting.com/installat...-fork-steerer/)

My commuter had its battery in the TT / aero extensions (before I switched that over to 105 Di2), Worked great, but the one down side is that you cannot take off the aero bars without crippling the bike :)
(https://bettershifting.com/installin...ro-extensions/)

Finally, there's the SM-BTC1... bottle cage mount for 11-speed internal batteries: https://bettershifting.com/component...ttery-sm-btc1/
You don't want this. It is bulky and I found it very messy... Sure, the battery is hidden away, but it's huge and you still have wires coming out of it.
The one good thing is that it has a 6-port junction built in. The downside of that is that you can have 5 e-tube wires enter/exit the thing.... :)

Originally Posted by Epicus07

Also how is this all connected? It’s a 2x system with a charging port in the handlebar end and what I believe is a battery in the seatpost. Is there a junction box somewhere internal ?

The handlebar junction A (EW-RS910) is probably connected to the shifters using the EW-JC130 Y-splitter (there are other ways, but it doesn't really matter). From there, a single EW-SD50 wire runs through/along the frame to the bottom bracket area.
There will be a Junction B (SM-JC41) somewhere around the BB, and the battery, FD, RD and front of the bike are all connected to that.

[commandcomm]

Great website Terry. It is very informative and easy to follow.

Slight thread hijack. I was looking into getting a di2 groupset for my rim brake bike, but after reviewing your website I am like ***. For Rim brake I have to run internal wires from from shifters to the battery, then from the battery to the derailleurs? Also, if I don’t have internal wire capable handlebars, I need a junction box….***.

Shimano di2 is not wireles as I thought. It easier to get r8000 components and run mechanical like the old times.

[TerryDi2]

Yeah... only the 12-speed disc brake shifters support wireless shifting, but even then, the derailleurs are still wired to the battery.

I am in the process of writing a page on the two wiring options for rim brake handlebars (https://goodshifting.com/installatio...fters-by-wire/ user: goodshifting pass: di2test), but it's not great.

For a fully wireless bike, SRAM is definitely the best option at this time.
(I'm not sure there are wireless SRAM rim brake shifters (?)).

My commuter bike is currently moving from 11-speed 6870 Di2 to 1x 105 Di2. Since it's a rim brake bike, it takes some messing around with wires and junctions. Especially since the frame isn't made with Di2 in mind.. there is no way to run two wires (shifters + RD) to the battery on this frame, and there are no openings between the BB shell and the down tube / seat stay.

I ended up putting a 4-port junction (JC304) in the down tube and connecting the shifters and RD to that.. and then I run a single wire into the frame to the battery.

[htwoopup]

Yes, Terry’s website is great. And he explained it wonderfully above.

That said, before I discovered the better shifting site I was confronted with your battery question.

If you have a non-di2 seatpost, there is also a ghetto way of putting a battery in it….wrap it in bubble wrap and put some tape around the bubble wrap squeezing the wrap and making sure it is on there. Obviously, use the amount of wraps of bubble as you need to firmly hold the battery in the post.

Another ghetto trick is run some thin diameter but sturdy string over the battery and bubble wrap inside the post with the two tail ends dangling out so that you can easily pull the battery out if you ever want to.

[rice rocket]

Originally Posted by TerryDi2

On my Di2 MTB I put the battery in the steerer - because I could .
My MTB had a dropper post, which wasn't hollow and there was no space for the battery. Putting the battery in the steerer works, but the ideal place is still the seat post.

Steerer for me too, so I can run the Ergon suspension post.

Just slims down the stems you can run, but there's still enough fit permutations out there if you're not trying to fit some retro aesthetic.