How can I disconnect a Battery Charger from the Battery while not Charging
Can this solution do the job of disconnection the charger if not needed and connect it if needed?


It has 'problems'.
All readily available MOSFETS have a reverse polarity "body diode" from drain to source. In the case of a P Channel FET connected as shown, the body diode will conduct when Vdrain is more positive than Vsource. Alas, this is the situation that occurs in your circuit when the charger has power removed. 

One solution is to use series connected opposite polarity MOSFETs with the sources connected and the gates connected. This arrangement is often used in LiIon cell protection circuits. 



10 uA drain is 8765 hours/year x 10 uA = 88 mAh/year
 = ~ 1.7 mAh/week