Battery Management Systems for Large Lithium-Ion Battery Packs
Section 6.2.3 Addenda
Often, the characteristics of a CCCV charger are less than ideal: when in the CV mode, the voltage is not perfectly constant, but varies with the current. This is due to the limitations of the charger's control circuits, and its internal resistance. Therefore, in chargers whose CV is set with a trimmer adjustment while monitoring its output voltage, you must make that adjustment at low current: either when the pack is completely full, or simply by disconnecting the charger from the battery.