its not charging

Anybody...need help..i bought the second replacement battery on eBay for my A1278 macbook pro 13, the first one i returned because i thought its not working, because it did not charged,and there is an x on the battery icon,then i test the second one and its not charging also, i am suspecting its the macbook problem, can anybody help me how to fix or diagnose the issue, i appreciate any help, thank you...