The time required to charge a battery depends on the battery type, the capacity of the battery, and the type of charger being used. A higher mAh battery will take longer to charge than a lower mAh battery. In general, it will take 3-4 hours to "rapid charge" a battery to the 80% level, and an additional 8 hours to “slow or trickle” charge a battery to the 100% level. A good approach is to charge your battery overnight for about 12 hours