Use this guide to replace your Retina MacBook's lower case assembly together with the battery as a single unit.
The battery is strongly glued into place and removing it from the lower case is beyond the scope of this guide, but it may be removed with a [https://www.ifixit.com/Store/Tools/iFixit-Adhesive-Remover-for-Battery-Screen-and-Glass-Adhesive/IF145-400-1|liquid solvent] and gentle prying.
'''To avoid logic board damage''', when your MacBook repair is complete ''but before powering it on'', [https://www.ifixit.com/Guide/Applying+Low+Voltage+After+Every+Repair+%28Retina+MacBook+2015+Only%29/107711|connect it to low-voltage power] using a 5-Watt iPhone charger and a USB-C to USB-A cable. These accessories are not included with your MacBook, so make sure you have them ready before you begin.
To reassemble your device, follow these instructions in reverse order.