While I generally prefer to create my own stuff, versus porting other's work, there seemed to be enough demand / desire for this, that I decided to give it a try.
I take no credit for the original mod, which is quite smart in how it was done, rather, I simply cracked open the applicable framework file (services.jar) to try and determine what was modified, and then worked to incorporate these changes, which were vast into our CDMA Hero services.jar file.
This will NOT change your battery icon / graphic in any way, it will simply add, in white text, the percent battery left, inside of your existing battery icon. While this is nice to have, if you are like me, you are now going to drive yourself crazy watching the percent value tick down!
The linked zip files, to be flashed via recovery, as mentioned, modifies a framework file, and as such, your initial boot will take a while after flashing, as your dalvik-cache will get rebuilt. This was built off of the Fresh 2.3.3 services.jar file.
FYI, since this modifies the services.jar file, the same file contains a previous mod I had done for removing the clock from the taskbar. As such, if you still do not want the clock in the taskbar, you will have to flash the mod that contains both changes (included below).
Downlad Percent Battery Used Mod <--- Flash via Recovery
Downlad Percent Battery Used Mod + No Clock <--- Flash via Recovery