I feel like Ebay is full of counterfeit batteries that tend to die out within a month or so and I have no idea how to filter out the bads from the goods - do I look for ones only in their original retail packaging or is there somewhere else I'd be able to buy these?
Just bought a "genuine" s5 battery on ebay and could visually tell it was fake. Using it and testing confirmed my initial suspicion.
I guess the only place to be guaranteed a genuine battery is a reputable seller - Samsung themselves or a telco store.