Are you running the carbon or alu seatpost?

I installed Di2 myself and I have the alu seatpost. I just wrapped the battery in packing foam (ask your bike shop, they will have it lying around from packaging, I used foam from a Bontrager part I ordered) and taped it and then shoved it in the seatpost. Hasn't moved and I have ridden on some rough road. Just make sure its stuffed in there and you should be fine

If you run the carbon post theres a battery hanger you can buy. But IMO you can just mcgyver it in and save the $. And the alu seatpost is fine, so if you have that, just wrap the battery in foam and save your $.

If you have not done a Di2 build though, its not straightforward. Do your homework especially if you are ordering all the parts yourself. Good learning experience though. I am glad I did it on mine!

Just do as the other poster said and wrap and shove it up there. I have thousands of miles on rough chipseal and it hasn’t budged.

I will disagree though and say Di2 isn’t hard to do. Do research to make sure you have everything correct. But actual install easy.

 
Thank you very much for your advice, but i am not some expert about bike technical thing and really with all the time that i spend training triathlon i dont have so much time to spend doing my own instalation, although i really like to have the time, but probably it would be and additional reason to face my wife’s complaint.
So, any specific advise about an special part to use or pictures about how you did it should be fantastic
For example do you think that the giant mount shown in the enclosed link could help me?

https://www.amaincycling.com/...er-150000049/p440697

True, it's easier than the mechanical groupo for sure. But all I'm saying is actually procuring the di2 is not easy, especially for me as I live in Canada. When the UK could send over parts it was much easier and you could pick the pieces but now your stuck with either bike shops ordering the whole thing or you can only choose from local shops; bottom line is its more expensive than before and you need to do research on what to order and size your cables right. But yea, the install isn't "hard" for any decent mechanic, but I wouldn't say the install is "easy" for the average triathlete who never does their own mech work.

Just wrap the battery in thin foam and stuff it jn the seat tube. If you are still confused let a shop deal with it. I don't really know what else to say man

You need a 9 series (carbon seat post) and the di2 bracket. It’s pricey (seat post is $200).

Part numbers shown here on page 4

http://trek.scene7.com/...t_Service_Manual.pdf

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Thus far, knock on wood, I've been able to procure things from Competitive Cyclists for Di2 that are somewhat comparable to the old UK prices whenever they have their stuff on sale (usually in the Spring). I've done two bikes now (one 3 years ago and one 6 months ago) with full Di2, including brifters, for under $1k.

Though being in Canada, no idea if you can have such luck.

And I agree with your last sentence. If you've ever cabled a bike, then Di2 is a cinch. But if you haven't, well it'll be a (doable) project. I actually thought the hardest thing about my SC build was the cabling for the front brake. It was a PITA to get it all lined up with the tight turns.