Your VAIO will use some power, even if it is completely shut down. This is per design and does not indicate a malfuction.
The two main reasons for discharging are listed below.
1. Certain PC components require sustained power to maintain operability, including for example:
- RTC (Real Time Clock), i.e. the mother board embedded clock, to keep date and time settings
- EC (Embedded Controller), i.e. the mother board power controller circuit, to control ON/OFF function and power saving features
- BC (Battery Controller), i.e. the battery pack microprocessor, to monitor the battery condition (charge level, temperature...) and to ensure the communication with the VAIO
2. Lithium-Ion batteries continuously gradually discharge, even if the battery is not physically connected to the VAIO.
The battery self-discharge rate will depend on the age and condition of the battery. Older batteries will discharge quicker compared to new battery packs.