Most of the "battery drains when laptop is sleeping" problems I've seen are actually due to the laptop waking itself up from sleep for some reason, then staying on until the battery is drained. You can usually tell this has happened because the laptop will remain warm for a short while after it finishes draining the battery.
Unfortunately, fixing it involves tracking down what program or service is waking it from sleep. And I haven't had much success at that. The easiest one was a wireless USB laptop mouse which would wake the laptop from sleep when moved. That's the behavior you want when you've stepped away from the desk long enough for the laptop to go to sleep. Not the behavior you want when the laptop is in your backpack, and the mouse bouncing around inside turns itself on and triggers the laptop to wake from sleep.