I am about to order the Shimano 9070 Di2 Group Set and install it on my current bike. The distributor has it in two forms, external and internal batteries. On my bike, the external would attach to a plate under the bottom bracket that puts the battery against the under side of the down tube. The internal fits into the seat post. From what I have read, the internal battery weighs less because it does not have to be weather sealed. Here are two questions I need answers to and have found nothing.

What process is required to charge the internal battery?

Assuming that charging means the additional inconvenience of pulling the seat post periodically, does having to do so outweigh the savings in weight and the visual disappearance of the battery?

Thank you in advance for your thoughts and they will influence my decision.

It charges through a port on the front junction box under the stem. No need to remove the seat post.

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My Cervelo R5

Thank you, I hadn't thought about that as a charging method, but it makes sense that Shimano did it that way. So now the decision is down to weight savings and esthetics.

In which case the internal battery wins on both fronts

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The front junction box needed is annoyingly expensive though, plus you have to spend another £50 on cables for the shifters.

I have the internal battery on my c'dale EVO and it is very neat and tidy, tucked into the seat post. I am looking at changing seat post from FSA to ENVE and when that happens the battery will be in the seat tube with foam around it to stop it rattling. Charge through port is simply plug in via USB cable. V happy

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Rides Cannondale System 6
Cannondale Capo
Masi Speciale (city bike)
2013 Cannondale EVO Di2 on order

BCR2 plugged into the junction box?

Thank you all for your quick responses. Of course the idea that the battery might rattle in the seat tube is a little frightening. I just spoke with Gita Bike and Pinarello has an adaptor for use with the Shimano internal battery, so my guess is that rattling will not be a problem. The Pinarello external bracket that mounts under the bottom bracket and against the down tube is made of aluminum, so I doubt that the internal battery adaptor would weigh more. That brings it all back to the weight differential of the batteries. The distributor has (30) 9070s coming in on March 31st and half are already sold, so tomorrow is decision time. Thanks again for the help.

No rattling possible with the internal battery, it comes with a push fit sleeve for most / any seat post.

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Riding my road bike in North Wales

http://www.strava.com/athletes/keith_robertson

Mine didn't come with a sleeve.

Ooh dear... All I know is I've seen a photo with the internal battery surrounded by a bulgy sleeve:



I've got a Di2 9070 group-set on order, so I hope mine comes with one!!

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Riding my road bike in North Wales

http://www.strava.com/athletes/keith_robertson

I got a new batt in the box and it didn't come with that butt plug or O ring.

can i install the battery in a cervelo s5 with aero seatpost?

I did get the two "sleeves", various washers and "C" clip. It all seems quite useless. Suppied directions make no mention of the items.
Seems Shimano was sweeping the floors and just tossed the stuff in the box.

I believe the bulgy sleeve in the pictures is from Trek and came with Madone 7k.