I'm having the similar issue with OEM battery I purchased from Amazon. My original Samsung battery was working fine for nearly two years, but it got swollen due to heat so I had to change it. I got refurbished OEM battery for S5 just looking like the original one.
But stand by drain seems almost twice worse. I used to lose 3~4% overnight on WiFi but it now loses 7~8% overnight without any setting change, new apps. Drain from screen usage, phone call also seems faster than before. Is this bad battery or should we normally re calibrate new battery like discharging to zero and recharging back to 100%, rebooting?