Why my notebook battery discharged itself alone?

I have a Samsung notebook with a dual boot configuration with Windows 7 and Kubuntu 12.04, and I mostly use Kubuntu.

Last night I fully charged its battery to 100%. After that I shut it down.

The next morning, 7 hours later, when I woke up and tried to turn it on, it simply didn't turn on. The LED on the power button stayed off.

Then, when I tried to turn it on with the AC Adapter plugged in, all looked fine, but I noticed that the battery level was at 0% now.

So I wonder, why did the battery fully discharged all the night long even with the notebook off? It makes no sense to me, shouldn't happen. I have had this notebook working for a month, when I bought it, and it never occurred before.

Do you guys have any idea what this issue could possibly be?

Seems like your laptop was not actually truly off. Try checking to make sure:

• That you are not in hibernate, and are truly turned off.
• That your machine doesn't have things that can cause it to "wake up" at random during the night.(like windows updates schedule)
• That your machine's bios settings are correct.
• That your machine's battery is not bad.

Try fully charging, and then removing the battery before you sleep for the night. If in the morning the battery is still dead then you know there's possibly a problem with the battery.