Coming up with ways to make you safer on the road, for Serfas lights this is a top priority. The new BLAST Audible Low Battery Indicator emits a loud 85 Decibel signal when your light battery gets under 10-minute runtime in that specific mode. How does it work? When the battery reaches 10 minutes of runtime, in its current mode, the light will emit a long beep followed immediately by a short beep. Sound will continue every minute. When the power button is pressed it will put the light in the next longest running mode and it will restart the battery low alert until 10 minutes of runtime in the mode is reached. Repeat as necessary. Example: Going from highest mode to lowest mode at first beep could extend runtime up to 5 times. Light will emit beep sound repeatedly when last minute of runtime in the current mode is reached. While charging the light the power button will blink blue. When full charge is achieved light will beep to notify charging cycle is complete.