I bought the ASUS UL50VT laptop at the beginning of 2010. At the end of last year, the original BATTERY that came with the laptop had some issues and I bought a new 12-cell battery for my laptop.

Now, my laptop always just cut off whenever my battery has a remaining of roughly 50% JUICE. Since it has only been 10 months since I got this battery, I doubt that it is no longer capable of holding charge. From what I experienced with battery that doesn't hold charge is that the battery indicator will just drop to 0% real fast, unlike mine which just cuts off at ~50%.

I did some research online and I came across some discussions talking about how the ACPI is not reading the battery charge correctly and a calibration has to be done in the BIOS. I tried doing that but realized that my laptop's BIOS doesn't have the battery calibration option in it.

I also came across other discussions which says that calibration can be done by just allowing the battery to drain off while on the BIOS screen. Then followed by a full charge of the laptop. This also did not seem to work (unless I am doing something wrong).

For the moment, I have disabled the ACPI and just checking if my laptop will last longer than 50%. Before disabling the ACPI, the windows battery meter was reading ~7-8 hours and it was at 93%. So if my laptop doesn't just cuts off at ~3-4 hours, then I was thinking that I could conclude that it is indeed the ACPI misreading my battery level.

In the mean time, I was wondering if any of you could help me diagnose this problem and TELL me if it is indeed a dying battery issue or is the ACPI reading my battery level wrongly?

Btw, when I mentioned that my laptop just cuts off, I do not mean that it goes through shut down, sleep or hibernate process. I believe it is the same as disconnecting the ac cable when your laptop is not connected to the battery.*UPDATE*

Before disabling the ACPI, the Windows Battery Meter and BatteryBar shows that I have 7-8 hours of battery usage. Then I disabled the ACPI and left the laptop running. After about 3 hours plus, my laptop just got cut off again. I connected the AC cable and re-enabled the ACPI and my battery was again at roughly half-bar.

If anyone has similar experience and knows what is wrong, do kindly let me know. I would really like to know if its a battery problem or just bad coding in the ACPI (that's what I noticed on several webpages).Sounds to me likt the battery has ONE bad cell.
Have you had it tested ? ?How do I test the battery out?Any local PC shop can do it...usually for Free.