Phone drains battery in 3-4 hours even when Power is OFF.

The battery fully charged and kept out of the phone discharges at the rate of about 5 - 10 % overnight.

When the same battery is inserted into the cell phone it gets drained to 0% in 3 -4 hours to the state when it cannot be recharged by the phone itself (external charger is used to charge the battery when it is drained)

When phone is in charging mode it gets rather hot.