Hello Venkatesh,
If your battery pack is not used for a long time, I would recommend to recalibrate the SOC by performing an open circuit voltage (OCV) measurement before the battery is used again. This will give you a pretty accurate indication of the battery SOC.
The self discharge could also be estimated provided your MCU has a RTC and is able to compute how long the battery has been in idle mode. If you have a modeling of the discharge over time of your battery, you can easily compute the self discharge of the idle time. But I would rely better on the first method because self-discharge is quite temperature dependant and temperature is a parameter that you won't have in the second method.
Best regards,
Philippe
