continuous battery monitoring during charging as well as discharging
I dont have enuf reputation to make a comment :( so i am posting this as an answer.

To get an accurate measurement of the battery capacity you also need to measure the current thru the battery. I would suggest you read about "coulomb counter".

and to your question regarding measuring battery voltage while charging using a voltage divider and ADC, I would say 'No' because you would in effect be measuring the charging voltage not the battery voltage.