Iphone 4 taking forever to charge. Don't know why?

So my brother just over a year ago bought a pre owned phone from gamestop that had a year guarantee. Recently the phone would randomly turn off. So he brought the phone to a shop and the guy said it was probably the battery. So he replaced the battery for him. The phone doesn't randomly turn anymore although today when he plugged it out of the charger it did turn off. But now with the new battery it takes forever to charge. Can't figure out why its taking so long to charge. Please help.

P.S The screen broke on the phone but he had it fixed aswell

If one of the charge port contacts is un-soldered it will make it charge about 1% every 10 minutes