There's an open source battery indicator that I greatly prefer to the default one. I was wanting to modify it to replace the default battery indicator. Is this even possible without building a whole custom ROM?
I do not believe it is possible without building a whole custom ROM.
Yes, it is possible to do without building a new custom ROM, but you still need root access. the .png files for the battery indicator are in the framework-res.apk, you can extract that, replace just the .png files for the battery and put it back with approriate access rights and it will work. kinda like the process to just can change the "Verizon Wireless" (or other carrier) text on the lock screen.
来源：https://stackoverflow.com/questions/1936742/replacing-the-battery-indicator-android