interesting thread with a wide variety of views / responses, some good some less so. My two penneth worth :- I run ultegra Di2 on my Genesis Datum, it has compact 12-34 cassette, this proves ample for most things but was defeated a couple of weeks ago by a couple of the climbs on the Knock ventoux. obviously the gearing would alter on the moulton but, I'm pretty sure there must be chainrings to suit. With regards the battery, it is internally mounted in the seatpost, I have never experienced any issues with it running out of power on a ride - even so I carry the charger and, a power pack just in case. After the LEL - which I did not connect the bike to a charge once, the battery showed as still having 60% power on the etube app. Even after last weekends london orbital - a total shift fest of short sharp hills, which I ece'd out and, back to make it just under 600km for the weekend, the battery showed at 85% when I got home. I had a bit of a mishap with the first battery which I broke when I removed it from the seatube rubber, it is quite amazing how little is inside the casing, the actual battery is the size of a single AA, which really amazes me how long it lasts for.