An user-interactive charging paradigm is presented that tailors the device charging to the user's real-time needs. The core of approach is a relaxation-aware charging algorithm that maximizes the charged capacity within the user's available time and slows down the battery's capacity fading. The approach also integrates relaxation-aware charging algorithm existing fast charging algorithms via a user-interactive interface, allowing users to choose a charging method based on their real-time needs. The relaxation-aware charging algorithm is shown to slow down the battery fading by over 36% on average, and up to 60% in extreme cases, when compared with existing fast charging solutions. Such fading slowdown translates to, for instance, an up to 2-hour extension of the LTE time for a Nexus 5X phone after 2-year usage, revealed by a trace-driven analysis based on 976 charging cases collected from 7 users over 3 months.