iphone 6 wrong charge

Hello
I have 2 iphone 6 who come for service because didnt charge.
I change charge ic (u1700) then it works and have good autonomy expect that is giving wrong precent when i plug charger.
For example if the battery shows 24% and I plug the charger then go to 45% if I unplug the charger go to 24 % if i leave the charger the phone charge correctly.
Any ideas?
In one phone I have change and the q1701,u1401 and still the same.