Battery not bad, but original?

I have this battery now already for a year in use: Samsung GT-I9000. With the naked eye, this product is not much different to the originally purchased Samsung brand.
Long-Term Test: As this is apparently here to a really well done replica, you realize until much later.
In the first few months, the battery lasted the promised 1 + 1/2 days. After 11 months the battery is faulty. Now needs to be re-creating a replica. The defect can be ascertained so far as the smartphone turns off after a few hours. The capacity thus falls rapidly and the battery can be only max. Use 2-3 hours. The original battery is very expensive, so will again grab "good replica" to such a. What more could you ask for under 10, -