Why does the VAIO computer consume battery even when the power is completely switched off?

When a computer with a fully charged battery is shut down and started again after few days, the battery has consumed a lot.

The battery will consume its power even when the power is switched off due to the following reasons.

1.When the battery is connected to the VAIO computer, it will use the power to backup the Real Time Clock (RTC) function.. 
2. The power button of the computers which are designed after PC97 has the function called software switch.
The power button does not directly switch on/off the computer. It simply sends the signal to the power control management..
Due to this software switch function, the power control management is always turned on and ready to receive the signals when the battery or AC adapter is connected. As a result, there's power consumption.

Note: PC97 is advocated by Microsoft, which is for better running of Windows 95, Windows NT and the other operating systems.

3. VAIO battery has a function to monitor battery status and to send signals to the computer regularly. This function works even when the power of the computer turned off.

The battery consumption for different models differs even in the same environment. The battery which has less capacity consumes power faster.