Currently I have a couple bikes set up to deal with having to share roads with cars. Both combine a 3W amber light on either side of the rear with a pair of TL-200's clipped side by side on the back of an Arlel rack bag. The amber lights have shaped beams and paint the road behind the bike. I run those day and night and just add in the TL-200's after dark.

On the touring bike a custom installation adds them to the back of a Thule rack. On the fat bike they're mounted at axle level which has the added benifit of lighting up the rear wheel. Although the lights themselves aren't all that visible from the sides - the road surface and wheel area they paint yellow definitely catches the attention of motorists and they give me lots of room.

Lipo batteries will hold their charge for a month, NiMh for 30 days and alcaline for years. Personally I like packs I can plug in and swap out.