Sorry for the delay - I just now noticed your comment.
All references to remaining battery capacity by terminal voltage measurement is the resting voltage with no charge or discharge and preferably with a waiting period before measurement. This is why using voltage as a capacity indicator is such a pain and less than precise.
Much better is an Amp-hour meter that keeps track of energy both in and out of the battery continously.
After an initial full charge, the one I use resets the read-out to zero upon the start of discharge, so the subsequent numbers are negative and increase with continuing discharge. When the net current is positive, indicating charging, the numbers decrease toward zero and if continued, go positive and increasing, indicating overcharge. Actually, you want to see some overcharge since the battery charge efficiency is not 100%.
The result is a continous indicator of where you stand on capacity. Please note that this should be refered to the ACTUAL capacity, not necessarily the new rated capacity. A timed discharge test should be done periodically to determine the actual capacity or you could be kidding yourself as to the percent of discharge.