Chosen Solution
My new battery only provides 3-4 hours of working time. When this Macbook was new, 5-7 hours was normal. Do I have a defective battery?
Did you do a SMC reset and the cycle the battery at least two times? Here’s the full story: How to Calibrate a Laptop Battery on a Macbook
Where did you get the battery from? If it was iFixit, duds are unusual but you probably got one. If if it was from a 3rd party, you might want to steer clear of those.
