Battery Spy measures the time it takes for your battery to empty. Monitor your battery uptime in a simple, accurate, and elegant way. The counter starts the moment you unplug your AC adapter. Regardless of whether you unplug it at 100% or 65%, Battery Spy will count down the time it takes for your battery to empty (or until you plug in your AC adapter again). It continues to show the percentage from the moment the adapter has been unplugged so you can easily track your battery lifespan, starting from any charge level.