So if your menubar is as packed as mine, you usually have to kill menubar utils just to get to your application menus (specially bad when I run Photoshop). SlimBatteryMonitor comes to rescue. SlimBatteryMonitor is a replacement power gauge for Apple’s Mac OS X that tracks both laptop batteries and many UPS batteries. Multiple-battery systems (e.g. older powerbooks) are supported as well. A graphical icon shows the power remaining, and can be accompanied by a text description (battery charge in percent, or time remaining). Colours can indicate whether the system is fully charged, charging or on battery.
Best of all, you can choose different display options for each battery state (fully charged, charging or on battery). You may wish to see the time remaining while on battery, for example, but show only the icon during charging, and hide SlimBatteryMonitor entirely when batteries are fully charged. SlimBatteryMonitor is a better choice because it presents the same information in a much more space efficient manner, allowing you to fit other menu bar items on the screen as well.