New batteries are hard for the device to charge; they have never been fully charged and are therefore "unformed". Sometimes the device's charger will stop charging a new battery before it is fully charged. If this happens, remove the battery from the device and then reinsert it. The charge cycle should begin again. This may happen several times during the first battery charge. Don't worry; it's perfectly normal.
The New Battery Isn't Charging. Is it defective battery