Rechargeable is good, but I like using AAAs. In flash mode on the Swerve I get 1000-1500 miles out of a set of AAAs before the light starts dimming. The light employs two so-called 1/2 Watt LEDs with lenses that produce a fairly narrow beam which is what makes it so bright. It needs to be aimed properly for max effectiveness which is the case with many of these taillights. Hanging off a loop on a backpack or seat bag won't usually cut it.