Does the battery protection circuit cut off when the battery gets too low?
In theory yes, but in practice no. The two LEDs are in series, and require 5.2V to draw any current. So as the battery starts to get low, it drops below 7V and Turbo mode is no longer full current (this happens at about 94% of discharge). As voltage drops further, the current keeps dropping faster. Below 5.3V the current is quite minimal, and eventually the LEDs are not driven at all (the converter will continue to run at about 1/3 of a milliamp). The end result is that as the battery draws down you get 30 minutes or more of gradually dimming light to warn you to change batteries.
