Re: my android phone charging decreses automatically why?
When is it decreasing? As the battery is charged, it's normal to see a charge rate slow down as it gets full. Think of the battery as a bucket filled with water. As you fill it full force, water will start splashing over even before it's truly full. By slowing the fill rate at the end, more water can fit in the bucket. It's roughly the same with batteries on a chemical level, and usually starts throttling around 75-80%.
If that's what you're seeing, it's fine. If it's at other times or erratic, it could be a bad USB cable, charger, or charging port.