So after a full 24hr charge the battery still isn't showing charged?? Is that what you are saying? And if this is the case, have you tried a different charger than the one being used currently?? And being the 4th or 5th owner of the phone shouldn't matter as far as the battery is concerned. Not unless it has either been improperly run down to nothing too many times and let die then charged, or the battery is just had its share of charges and may be showing it's age if it was used a lot by the previous 3-4 owners. But if taken care of and not charged more than the life cycle of the battery, it should charge up to 100%.
Like I said before, if you have a way to take it to a Best Buy or an Apple Store, they may at least be able to help you better being able to actually have a physical look at the phone.
I would try what J.A. has stated to do as well and force start the phone. That or turn it off and let it charge that way and see if it makes any difference. And also if you have a different charger setup, use it. See if the results stay the same or change. Might be a faulty charger. Most likely not, but you never know. Hope you get it resolved and working correctly. Have a Blessed Evening.