The phrase "battery level" refers to the amount of power or energy remaining in a battery. It indicates how much charge is left in the battery before it needs to be recharged or replaced. Full definition
Once you make your preferred changes and apply the wallpaper, you'll notice the water level will fluctuate depending on the current battery level of the device. (android.gadgethacks.com)
There's a button on the side to turn it on, and you'll find a typical four LED battery level indicator on the top. (digitaltrends.com)
The digital assistant can now inform about missed calls and phone notifications, while soon she will notify users about low - battery levels on connected devices. (windowsphonearea.com)