A new battery should be charged for 8-10hrs for the first 3-4 times; this makes the battery seasoned for better results and longer life.
Battery should be charged only when it gets fully discharged since all the batteries are designed for certain charge cycles which should not be disrupted by semi charging.
Also, a half-discharged battery appears to get charged quickly and gives a false impression of getting fully charged when it’s actually not.
When you put such a battery into use again, it drains very fast. After the initial charging to season the battery, you should follow the normal charging procedure given on the handset or user guide.