Charge 14.8V battery with 19V voltage
There must be 1 step down converter with current and voltage control for the battery pack ( which is most likely dead or very weak) and then many step down regulators for the motherboard for CPU, GPU, RAM, I/O. So the 19V is just a universal charger + mobo driver voltage and you're just reading the voltage just stored by the charger there recently, which you ought to be able to pull down with xx K resistor as it ought to be reverse current diode protected.