I have similar issues with a different make of charger when I attach a large capacity battery to it.The charger is supposed to turn itself off once the battery is fully charged,yet despite being left for about 11 hours,the charge light remained on.The battery tested as fully charged on a multimeter & the Vamo,and performed the same as a similar battery charged on its correct charger(approx 6-7 hours)but unfortunately,failed during its next charge(wouldn't accept any charging,and didn't hold enough charge to work on the Vamo)so was disposed of(no biggie as was an ex-laptop battery)
I am no expert on such things,but I guess the internal electronics of the charger was "confused" by the larger capacity and tried to get it to produce the same reading to its electronics as the lower MaH battery.