Portable battery packs or power banks have become increasingly common in recent years. Whether you are out for the day or on a long vacation, a portable battery pack ensures that devices like smartphones, earbuds, and even laptops don't run out of juice. But when it comes to charging the battery pack, it can sometimes take longer than you expect. Also, keep in mind that the power bank's capacity plays a major role in the time it takes to fully charge it. Additionally, charging a battery pack while drawing power from it simultaneously increases the charging time.