Updated for what is a finished Brompton. Almost two years duking it out through midtown gridlock with this contraption and still livin' to talk about it.
My frugalness had insisted on reusing an old NiteRider Digital from the ancient past. A homemade battery pack of 13 nickel-manganese C-cells fueled the NiteRider LED rear flasher and, when the halogen (HALOGEN!) front light was turned on, about 2 hours of run time! Just enough juice to get me far enough away from home after dark to get me lots of time to get killed with no lights on while riding all the way back home!
So the Brompton has been upgraded for modern LED lighting from Dinotte. XML-2 headlight and the Daytime Red Taillight. Anything to skew to odds towards greater visibility and survivability in Manhattan traffic. Although I don't consider Manhattan the riskiest of traffic to ride in because the traffic density rarely gives a driver enough time to text or use a smart phone. Cabbies cutting/short stopping for fares is something else.
Also installed a Sugino single chainring crankset to allow me to spin 175 crankarms. This is as close as I'm gonna get to making a Brompton ride EuroPro like my roadbike.