Comment 59 for bug 177570

(In reply to comment #7)
> This all is fixed. Since the kernel send no signal if the battery values change
> (because the values get read from the hardware and set in sysfs in the moment
> you read a file there) HAL do the same as before with proc: read battery values
> every 30 seconds which is often enough.
>

I think you should consider to make the poll interval configurable or put some heuristics, e.g., poll every 2 minutes when battery is above 50%, poll every 1 minute when battery is above 10% and poll every 10 seconds otherwise.