Hi dude,
I have a 751JT and also replaced the battery. Actually I changed the battery 2 times, first time it was some exact copy of asus original battery with nearly 0% charged.
I didn't managed to charge the battery.
The second time i got a Chinese non-copy of the battery. By now, the battery is charged at 100%.
I will see after a few days of gaming if it has worked out.
Problem is I think there is also some ****ty nvidia driver issue. I heard there is some extra consumption with the latests garbage/thieves/no making decent driver for linux/ NVIdia Driver.
(see here the post from CosmicBoy
https://fr.ifixit.com/Answers/View/309232/Laptop+will+not+charge%2C+does+not+recognize+power+cable)
What is the software you're using?
Please let me know of your situation.