Help - LG G3 Battery drainage and flickering screen

[Android Central Question]

Hello, I am am hoping someone can help?
My LG G3 battery was draining in 4 hours with almost no usage. Checked all the obvious stuff. Assumed battery was rotten.
Bought a new official battery. However the new battery will not charge, the screen simply flickers. With the old battery, the phone does turn on at least.
The batteries look identical. I am confused as to why the the behaviour would be different.
Does anyone have any ideas?
Thanks

 

[Rukbat]

The original battery is about 4.5 years old, so it's probably shot. But the "new" one has probably been sitting on a distributor's shelf for 4 years, so it's probably not in great shape (which is why people replace phones - you can't get new batteries for old phones).

Try charging it overnight - don't try to turn it on. If it turns on after an overnight charge, use it until it either tells you to charge it or it turns off. Then charge it for at least 5 hours. Do 3 full cycles of that. It may - or may not - recondition the battery. It depends on how long it's been sitting, and under what conditions. (Cooler conditions, with a 50% charge, are best, but after 4 years, there's probably no charge left - and if the warehouse is typical, it can get over 100°F in the summer.)