I usually plug my A1 in overnight, but last night it was on my desk, and I left it unplugged with about 80% of power left. Eight hours later I return to find that the battery level was very low.

I had assumed that when a tablet or system is in Sleep mode activity it idles activity. Why is my battery then drained? Should I switch my tablet off when it is plugged into the AC?

The above symptom may occur on the following systems:

IdeaPad Tablet A1

What happens to your tablet when it is in Sleep mode depends on a number of parameters. The CPU is put into a low-frequency state, but things still happen.

• WiFi Sleep Policy: You can have this set to keep WiFi on while the tablet is off or turn off about 15 minutes after the screen turns off. If you want email notification while the tablet’s screen is off, you’ll need to leave WiFi on.
• Background Data Sync: If you have this turned on, the device will regularly check for updates to email, calendar, weather, news etc.
• Other polling applications: Some applications will poll for new data with very high regularity. Settings for the the polling interval are, however, adjustable, so have a look at your apps, even those that came with the device that you haven’t used. Check your apps’ settings in case they may be downloading data periodically even if you aren’t using them.
• Bugs There may be an application with what’s called a "wake lock" that keeps the CPU in a higher-frequency state even with the screen off. Do a quick check online to see if this is replicated in other users’ systems.

There are apps that can help keep battery usage down. Some apps can turn off the radios (WiFi, Bluetooth) during sleeping hours, which would not only save power by not powering the radios, but keep apps that rely on an internet connection from sucking up your electrons. You could set sleeping hours from just after you usually go to bed to just before you usually get up ... that way, when you wake, all of your apps are up just a bit earlier for their updates. There are lots of other power management apps in the market if you look around.