I have a Galaxy Note 4 with 2 batteries. Both are OEM batteries. I purchased a spare last year but only used it once. The original battery that came with the phone is working fine and light turns green after charge reaches 100%. I used the spare battery the other night but after charging it to full capacity, the red light stayed red, it doesn't turn green. I used the same battery yesterday and let it run down until the phone powered off, then recharged it. The light still did not turn green? I took that battery out and put in the original battery that came with the phone. The green light is on since the battery is charged 100%.