mobile

Hi, I'm new to posting thread. So, I had battery drain problem and I was one of those people who is surfing through the internet trying to find solutions for battery drain problem on Note 4. Yesterday, I took out the cases and battery to clean out the dust. Later, when I put back the battery and turned on my phone, that's when the magic happened. My battery problem was fixed and I was surprised and now when my screen is off it takes about 1-2hrs or MORE to decrease %'s. When I use my phone constantly, it takes 5-9 mins for each % to decrease (WHICH never happened for me.) I charged my phone last night @ 11 PM (04/05/2015) and I still have 68% through medium use. I still have 1 DAY and 22 hrs left on my battery according to my phone. (Screen time on: 1h 14m 16s). I'm very happy with my phone right now.

Here is my question: Can anyone give me explanation to this? How can just taking out the battery and put it back in can make huge difference?

NOTE: I'm not complaining; in fact, I'm really happy. I'm just curious and a lot of you smart people probably has the answer to my question.

Thank you for reading!:D