"Faultless, excellent and a very good choice" [Review: ARCC Conversion for Bromptons]
I had converted a 6-speed Brompton. I find that one of the cables catches continually on the rear derailleur casing, so I have to be careful. I ordered the lower capacity battery, and all-in-all I get 15 miles out of a charge. Though range depends on lots of things, particularly assistance settings, it can be difficult to gauge which battery is necessary. The battery charges from flat to full very quickly.
I asked ARCC to supply and fit a larger Brompton chain wheel, which they happily did: I *really* appreciated their flexibility to accommodate requests. I like the fact that I can manage settings from my smart phone, rather than the supplied remote control, and even more the fact that the on-bike computer remembers settings, so I don't need to re-set them every journey: Let's face it, commuters generally stick with the same settings, and just want to get on and go.
As the bike is electronically assisted, I find that I don't use many of the gears, so if users are buying a Brompton for conversion, I'd just go with the 3-speed; I would say 2 but have reservations about the cable catching as mentioned above. I find the bike eager, and fun to use, a pleasure. It handles slopes exactly as one would want, well.
I have had no problems or niggles in the time I have had it: the ARCC conversion was faultless, excellent, and a very good choice for me.
Photo credits: Richard Peace