I'll give it another try in this afternoon but do you think that when current is flowing to the battery, voltage is dropping and causing the max to reset ?Is your V+ high enough?
From the datasheet :-
"Choose an external DC power source (e.g., wall cube). Its minimum output voltage (including ripple) must be greater than 6V and at least 1.5V higher than the maximum battery voltage while charging.
This specification is critical because normal fast-charge termination is ensured only if this requirement is maintained ".