Lipo charging is in two phases - the CC part and the CV part. What you saw was the CV (constant voltage) part where the charger holds the lipo at max voltage while it 'tops' off. During this stage you'll see the current falling to a small value near zero before the charge terminates.


Here's something fopr the OP to read -

http://www.rchelicopterfun.com/rc-lipo-batteries.html