the normal battery indicator is even more corrupted on my N900 since i only charge my battery with an external charger while the battery is in the phone, my own QBW script works fine like this since it only goes by the current voltage of the battery but the standard battery meter goes nuts and doesn't update for a long time.
One thing i used to do was to launch H-E-N and close it again since it stop & starts BME, this will update the standard meter.