Voodoo Battery is mainly known for two reasons: it works on almost any system, and it has bugs.
However, this is the simplest way to get a battery meter on an hackintosh (tested on Mavericks and iAtkos ML) and bugs can be worked around easily.
Download VoodooBattery ZIP file, extract it and you’ll get a VoodooBattery kext and an AppleACPIPlatform kext. But, before installing these kext, we’ll have to inhibit Apple’s default battery management system; this can be easily done by removing /System/Library/Extensions/AppleSmartBatteryManager.kext (AppleACPIPlatform.kext is going to be overwritten so there’s no need to delete it now, however you should backup it too).
Now, just move VoodooBattery.kext and AppleACPIPlatform.kext we extracted from the downloaded ZIP on /System/Library/Extensions.
The system should be ok, however you may want to rebuild the kernel cache to avoid issues: this can be done with Kext Utility (or similar tools).
Now, after rebooting, you should notice a battery icon on the system tray. After using your system a while, you’ll notice that it has some bugs: on my PC, for example, it didn’t detect when I plug or unplug the charger. The charge level is detected correctly, but the default battery icon just doesn’t show it when the battery is charging, and it thinks that it’s charging even if it isn’t, so we’re going to use another battery meter.
My choice is SlimBattery Monitor, a simple tool that’s easy to customize; I set mine to always show the battery percentage so, even if it thinks it’s charging, I can always see the real battery level and avoid the “wrong charging icon”.
However, you prefer you can just set the default icon to show percentage too.
To hide the default OS X icon, just go to Preferences, Energy Saver and untick the proper option.