The batteries are different and at 17 cycles is most likely not the issue. It's also a very difficult replacement. Here's some info on it: http://www.everymac.com/systems/apple/macbook_pro/macbook-pro-retina-display-faq/macbook-pro-retina-display-13-how-to-replace-battery.html
First see if you can get a better idea of its status by downloading and running Coconut Battery:
http://www.coconut-flavour.com/coconutbattery/