Samsung Galaxy S3 Battery Charging Issues

[AC Question]

I have an interesting problem with my phone. The battery drains in 3-4 hours, even if phone is switched off or is idle. So, I ran a test if this was battery issue or phone software issue. My friend has a Samsung Galaxy S3. I took a battery from him that he charged using his phone. Put the batttery in my phone and gave him my battery. His phone discharged quickly. My phone didn't discharge till night. Then, he charged my battery using his phone. I charged his battery using my phone. We exchanged batteries. My battery (charged by his phone) worked OK. His battery (charged by my phone) discharged quickly. Clearly, we have an issue with how my phone charges battery. It does show 100% charged. Either, the charge is not complete or it is creating a leak or something else is wrong. Can someone help?