Thank you for you most liberal suggestion. Somehow i googled and found that the problem with the battery pack is not with the cells itself but the circuitry itself. this may be some dirty self destruction tech from the manufacturer. I managed to find a similar circuitry and the battery pack is now working a great deal of about a hour and half backup time.
I am from Imphal, Which is quite an tech unexplored place and hence no good dealer nor retailer of Dell exist here hence too hard to find a good battery pack (original). none of the online sellers too delivers to my place.