you can surely find a battery that will fit in the seat post of seat tube, but you will probably need to find a custom one. This is commonly done, if you google around you should find some options and tutorials.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

Nope, the Jack man is right. You have to go full custom on the battery if you want it inside the post. For me when I do custom mods on these bikes I put the standard battery under the left chainstay by the BB. Works very nice and clean, especially with Ultegra E-Wires. Also the right stay/ rear derailleur wire is much, much easier to use the wire cover and run it external rather than drill holes for internal. You can completely hide the wiring so just as much is exposed as would be if run internal. The front section is easy. and the internal e-wire box stuffs up into the frame fine at the BB. So you can get a clean mostly internal with no warranty killing frame modifications.

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Retul Certified Master Fitter, FIST certified fitter, Owner of Hypercat Racing http://www.hypercat.com, and friend to the animals.

can you that on the p4 as well without drilling???

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Ziv Sade
IronMan Age Grouper & Endurance Athlete

Philip,

Dumbass question... I've swapped cranks on my P3 a few times but have never taken out the bottom bracket. I'm assuming that the access for the e-wire box would have to come through there, correct? I can't see any other way to get a junction box into a P3's BB area.

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Edit: dumbass question answered by reading the Shimano 6770 dealer's manual. Looks like I need to get some bottom bracket tools!

Thanks for the feedack. I'll study the options and go from there.

Pricey, but can always use Calfee for a complete custom internal set-up.

No. I did install Di2 on P4 and it was relatively straightforward but did drill holes. If you search the forum you can see how I drilled and pictures. If any questions feel free to send them.

I did use a custom battery. I recently purchased Di2 DA for my new bike and now realize my custom battery fits inside the seat post on my P4, was way cheaper than the Shimano battery and should last three times longer. $150 for battery and charger with Shimano is pretty ridiculous, IMHO.

BTW, I would install a fuse or PCB if you go custom battery route.

the new Di2 internal battery is TINY, it fits (with a lot of room to spare) into a 27.2mm seatpost, I would be shocked if you could find a seatpost it will not fit into. You can get all fancy with a custom housing, pay 3x the price of the battery to have Calfee do it, or you can just do the install yourself , wrap it in a little foam if you need to get it to sit tight.

The Cervelo P3 seatpost is a challenge due to its thin torpedo shape. It is a tapered opening with a max width of 20mm or so.

Calfe is not an option for me as I can not bring myself to pay $600 + 50 installation for an internal battery.

I do have a question for any electronics guys:

Can I buy a custom battery that will fit inside the bike, then solder the wires off the battery to a splice onto the EW-SD50 cable wire going to the SM-JC41 junction box??

I can buy a battery with exact voltage and mah rating for $20 on line that is thin and would easily fit inside my seat post.

Is it as easy as cutting the EW-SD50 cable in two and having two wires, one to go to the positive and one to the negative of the battery terminals. If so that would be a 15 min job for me.

FWIW I just measured and the Shimano battery is 17mm at it's widest point...

17mm just might fit. I'll measure with some calipers and see. Can you tell me the length and capacity of the battery??

Still might go down the custom battery route if I can just to save some $$. A battery with circuit protection is just $20.00 as compared to the $200 for the Shimano Battery. But it would save lots of time and hassle.

Anyone know where the SM-BTR2 batter is in stock??

not aware of any places in the US it's available yet but bike24 has it in stock and I think ships for free

Ultegra Di2 has a CANBus chip that allows the battery to power the system. The original 7970 didn't have that which is why you can make your own battery.

In order for you to do your own custom battery you would need to purchase the battery mount (at least $100) and either remove the chip or rig it up to the mount. You won't save much in the end unfortunately. See the thread below for more info on the battery mod that another member did on his bike.

http://forum.slowtwitch.com/...egra_Di2_TT_P3754167

The easiest way to do it is to just get the shimano BTR 2 with the new 3 or 5 port junction. The BTR 2 has its own battery charger as well. I'm not sure if you can sub in another charger.

Will not fit. Contact Calfee design.

PlasmaTT wrote:

Will not fit. Contact Calfee design.

I contacted Bike24 and they gave the dimensions of the Shimano SM-BTR2 internal battery as 17mm x 160mm.

You are correct in that it will not fit inside the narrow seatpost as it is about 16.5mm or so.

But I made an 18mm x 160mm mockup out of an old bolt and it DOES FIT inside the Seat Tube. So all I need to do is find a way to drop it in once its connected and have it secured with foam or velcro. Since the new SM-EW90-B junction box has an external charging port there is never a need to take the battery out other than to replace it once it will no longer hold a charge.

I hate to go the Calfe battery route as I contacted them and the cost if over $700 for a battery and charger as opposed to $200 or so for the Shimano Internal Battery.

Does that reasoning make sense? I'm learning all this stuff as I go along.

$700 would include a lot more than the battery and charger! That sounds like a full boat retrofit with everything. Have a look here for pricing: http://www.calfeedesign.com/...d-Wiring-System1.pdf

I'm at the official Shimano 9070 media launch for the US now. The Shimano guys say that more and more manufacturers are going to be offering their own internal battery accommodations and seatposts (and of course, Shimano will be offering their own PRO round post that is specific to the battery).

For 'ghetto' retrofits on existing bikes, they said that spray-in insulation works really well - assuming the post is wide enough inside. Your battery gets stuck there forever (well, probably), but it apparently works well. You'll want to leave the wire a little long to accommodate changes in post height - which *might* rattle around a little bit... but I doubt it'd be very noticeable.

FWIW, we've spent two days riding on the new 9070 and all of the new wheels. The new Di2 is... in-sane. Price went up ($4125 for the complete groupset) - but sheesh it works really well. Wheels are a huge step forward, too.

Craig, maybe I misunderstood the person giving me the pricing. Sorry my bad. The pricing options page shows I could probably have gotten away with $595 plus installation. The Ultegra module is a huge percentage of that cost. I believe Devona said it was required for everything to work.

Well I actually found out the Shimano Dura Ace SM-BTR2 internal battery fits inside the Cervelo P3 seat post perfectly. It is super snug and the rough carbon surface inside the post actually acts like velcro and holds that battery firmly in place. I have to use a lot of force to take it back out if I want to.

Using the SM-BCR2 charger/interface I am able to do on-board charging and programming/firmware updating on the system. So my system is up and running and I am very happy now with how it looks and how it operates.

I built the battery for my Di2 system. Cost was around $25 and then another $25 for the charger. I taped them together and they fit inside the seatpost on my SLC-SL. I just clipped the wire going to the battery harness and attached the connector as shown in the second picture. I got that from Napa Auto Parts. It's a connector for a trailer hookup I believe. That couldn't have been more than $5. I have been using this setup for over a year.

Wow Nice. I like to go DIY when possible myself. But I was told this would be challenging with the Ultegra 6770 system because of CANbus circuitry would not allow you to just plug in an equivalent DIY battery instead of the OEM battery which has built in circuitry to work with the CANbus.

Well that's a good reason for me to not upgrade to Di2 11 speed then.

Hi, OK, different bike, but same concept. I just installed the Ultegra Di2 system on my Trek Speed Concept about a month ago, and put a small battery pack down into the seat tube. I used the standard Ultegra battery mount (with the canbus electronics), but trimmed the size down to slide down into the frame. Like others have done, I soldered lead wires to the connections on the battery mount and ran them up and out the top of the seat post (I had to drill pass-thru holes in the aluminum seat mount base) as shown in the included pictures. To charge the battery, I just unplug the connection as shown and hook the charger up to it. When finished charging, I just plug the connections back together and secure the connection to the bottom of the seat using a piece of velcro as shown, this keeps everything tidy and out of the wind. You will also notice a small rear light (trimmed down Bontrager brand) that is on a custom mount to the seat post mount. The battery I used is included in the link below. I think the total cost for the battery, connections, and charger were in the $60-$70 range. This worked out really well and was not to difficult to do. I hope this might give you some ideas. Glen

Battery: http://www.all-battery.com/...tterypack-31145.aspx

I agree it is painful to pay $300 + for OEM or custom battery/charger that could be bought for $30-40 if the circuitry would allow.

I'm sure there are more technical folks out there that have or will have the DIY process to easily do this. I just took the lazy way out and bought the OEM stuff.

I am about to go down the same path, and was wondering if/how you were able to fit internal junction box? Also did you end up with the battery in the frame or seat post? THanks in advance