Battery Clock is a free Android utility tool that features a beautiful battery widget that also functions as a clock. It is designed by BrainCrash Soft and is available for download on the Google Play Store.

The widget is resizable and comes with high-quality graphics, with a radial representation of battery percentage and numerical battery percent displayed on the widget. Users can customize all the widget colors and transparency from the app, and it also shows time and date. Tapping the upper part of the widget opens the alarm feature. Additionally, the widget has an option to show charge/discharge time left, and discharge prediction that estimates how long the battery lasts.

Moreover, the app has graphical history of battery usage, including battery details like temperature, voltage, health, status, and more. Users can also configure every detail of the widget using the widget designer. However, users are advised not to use task manager, task killer, or other power-saving features that are often built into the system as they may affect the app's performance.

Overall, Battery Clock is a light and optimized app that should not drain your battery. It is important to note that home screen widgets will not work if the app is moved to the SD card due to the limitation of the Android platform.