I have this problem too. Normally it jumps from 88~92% to 100%. When this happens, I just power off the device and wait for the 100% signal on the screen, then I power it on again and wait for the warning to unplug the charger.
Maybe a battery calibration can solve it, but I didn't try yet.
Your thanks are far by just one click :_)
Device: Galaxy Grand Quattro (Galaxy Win) powered by stock rooted rom