Macbook was lying about the battery

My Problem

The OS and charger light would indicate the battery was charging, but it wasn't. For example, it would report 85% then if I unplugged it would suddenly drop to 10%. Sometimes, when I thought I had plenty of charge, the battery would completely go dead and the the laptop turn off.

My Fix

Many steps, but easy to follow.

My Advice

Use an egg carton to sort the screws by step. If you don't have a spudger, whittle one out of a chopstick.