Here is the lighting system on my Bianchi Volpe, one of my too-many bikes. I ride the Volpe a lot, and one reason is that it does everything with aplomb. I run the lights day and night because the cost is imperceptibly low: I can't feel the drag that the generator hub creates.
On my bikes without generator systems, I love
this battery-powered light.
I use a Cygolite Hotshot as a battery-powered tail light. It can go steady or flashing, and there is a choice of flashing patterns. It is very bright. Both the B&M Ixon and the Hotshot last for several days on a USB charge, largely because they both have lithium-ion batteries.