Battery problem in just 2 years and 3 months - skoda rapid

Hi, I bought skoda rapid on October protected. It's just protected months and I discovered that the battery was disclosed bad by the service center here at Gurgaon. I was really surprised when told by the service engineer that the life of the battery for Rapid diesel is just 2 or 2and a half year, which is not understood by me. I have taken extended warranty but they say battery is not covered. My car runs approx protected kms on daily basis which clearly indicates the reason for the failure is not usage. I am really disappointed and have decided to buy it from outside so that the duration is justifiable. Need your help in getting this sorted out