BatteryBot is the original battery indicator app for Android, released in 2009 as simply "Battery Indicator". Both the free and the Pro versions have maintained a 4.5+ star rating in Google Play from the beginning. It offers two modes: the original status bar indicator and now also a desktop widget. You can use either or both, as you please.
For those who want more than is offered in the free version, or for those who just like to support small, independent developers like me, this Pro version remains lightweight while packing in many useful features:
BatteryBot Pro monitors and shows your battery charge level (percent) as an icon in your status bar, with temperature, health, voltage, and time since plugged / unplugged in the notification area. It also has user-configurable alarms, logs, and widgets.
• Automatic time-remaining estimates based on recent usage
• Several icon sets (including fully configurable green, amber, red, and black icons)
• Small (1x1) and large (4x1) app widgets
• Notification (with status bar icon) is now optional -- can be used as just a desktop widget
• Battery logging. You can log the battery state (charge, status, voltage, temperature) and browse the logs on the phone or export to CSV.
• Manually or automatically disable / reenable device lock screen / lockscreen / keyguard
• Alarms (full, charge above X, charge below X, temperature above X, or health failure)
• Control the notification priority on Android 4.1+ (For example, you can set to "minimum" to hide the icon but keep the notification in the tray.)
• Lots of configurability of behavior and appearance.
• The charging indicator (the bolt under the number that indicates when the device is being charged) for the sets that have it is optional in the Pro version.
• Very lightweight (please email me if you think otherwise, and I'll help you figure out what's wrong — I promise this app will not drain your battery!)
• Shows 1% increments even on most Motorola devices (option needs to be enabled on devices that default to 10% increments)
• Well-tested and supported on all major versions of Android (2.1, 2.2, 2.3, 3.0, 3.1, 4.0, 4.1, 4.2; Eclair, Froyo, Gingerbread, Honeycomb, Ice Cream Sandwich / ICS, Jelly Bean) and form factors (small phones, medium phones, large phones, 7-inch tablets, 10-inch tablets).
• Open source
• Added Japanese translations