Battery drops from 100% to 7%
I bought this phone from eBay. Turns out it would only turn on unless I charge it for hours! So I bought a new battery and it began charging and turning on. I disconnect it and it would be fine for like 2 or 3 minutes. Then it would all of a sudden drop from 100% to 7%. I don't think its the battery because I bought an OEM battery. But it could be defective. I'm not sure. Any help?