> drains really quickly when it is shut down or on standby
Without AC adapter plugged in? Ever tried removing the battery and leave it alone for days then test the batter again to see if it has been drained up?
> When I am using it, the battery is great.
Without AC adapter plugged in?
the test i mentioned above will tell you where the problem is located, the battery or the computer. So we can address the issue accordingly.