I would like to be of help, but I'm not sure if there's any other way to get the battery charge reading other than executing
gasgauge-info -m. Like I said, it's probably not accessible via lipc properties and you'll have to find a way to get the output of the shell command and then display it in the status bar.
For a start, these posts (
1,
2) look promising. I'm just not sure if any more info on this is available, or even source code of a project that has a similar implementation.
Also, I would imagine it would have to be refreshed periodically using a script, because there isn't a such event that would allow automatic updating (as opposed to battLevelChanged which provides the percentage, for instance)