phone wouldnt charge replaced charge port and battery now when I plug

Girl brought a iPhone 5c in dead. Replaced charge port and battery now phone recognizes charger and I have the charging indicator in the battery symbol on display percentage never increases. Girl had gotten phone from friend who told her it would shut off at times and power back up only when it felt like . Could these issues be a manifestation of the well know u2 issues or a fusable link backfeeding the battery? I have bought the 5c schematics from apple unlock just hoping to avoid 3 or 4 hours of chasing electrons. ?