I have a notebook from Asus which is about to make its second year of life. I have absolutely no problems with full battery capacity, which is about 2 and a half hours, only 30 minutes or so less than when it was brand new.
The problem is it shuts down for low battery with more than 30% of battery left, according to Linux and Windows. I can confirm this because, after some minutes turned off, I can still "force" it to turn on and last some minutes before shutting down again. Repeatedly doing this, I managed to get as low as 4% of battery, so I am sure the battery is still lasting as it should, but it's "critical level meter" is faulty.
It is not the system that turns off, as just waiting the battery to waste while watching the BIOS still triggers the shutdown.
What can I possibly do to fix this issue? I am not really into the mood of contacting Asus support, they make me wait a lot (last time, over 2 months) and my warranty is already over.
More info: Battery is 19V @ 3.42A Notebook is an ASUS K43BY The computer just turns off, there is no warning (it's even before the SO warns low battery), it's like it has ran out of power all of a sudden.