There's no point in buying batteries from Ebay or Amazon anymore because there is almost no way of making sure they are real before receiving them. This is true for cell phones, laptops and everything else.

I bought a couple of laptop batteries for my old Sony Vaio laptop that claimed to be OEM, original, etc and they were fake. And no, I did not go for the cheapest ones, but the most expensive from sellers with a lot of positive feedback.

As a side note, the reason I stopped buying Sony laptops were their batteries. Replacement batteries from Sony are EXPENSIVE when compared to Asus for instance. And they don't last any longer in terms of both run time or longevity...