Question: Hi Tekdep, I need battery for MacBook Pro Retina, 15-inch
If the case has just started to swell, does it need to be replaced with the battery.
Answer: If the battery is expanding and making trackpad clicking difficult than it may be a good idea to replace it,
sometime battery can break the trackpad and damage internal when its expanding,
Overall expending battery is sign of bad battery that needs to be changed sooner rather than later,
Please make sure you know how to replace the battery and take all safety measures or let computer tech do the installation.
link to To different Battery Models For 13 & 15 Inch MacBook Pro,