INTP:
voltage potential automatically stops charging, so if input voltage matches battery voltage, there isn't any movement to quantify this 'keeps trying to charge' idea.
I've wondered about that too. I suspect that efficient charging requires a voltage considerably higher than the target voltage for the battery, which would of course damage the battery once the battery has reached full charge. I'm curious about how well the battery would charge if, as you propose, it's charged by a source that's fixed at the target battery voltage.