MacBook Air startup problem(s) Earlier today, I replaced the old, worn out battery in my MacBook Air to a newer one.

Upon startup, the fans within the computer went off at full speed and the entire computer is laggy. I have attempted to restore my computer from a Time Machine backup by holding both Command+R and Option (two different startup times) to which both have arrived at the current result I'm at:

My MacBook Air does not go past the initial startup screen and is stuck with a 0% progress bar.

I've attempted to restart numerous times and I'm fairly certain this isn't helping anything. I assume that the high fan usage is due to the CPU being overworked, but what would be using the CPU that much on a startup?

My question is, how do I go about fixing this? Attempting to enter the macOS Utilities causes a road block before I even start to progress there.

Specifications:


MacBook Air
Mid 2012
latest public macOS release
The third-party battery was too powerful, despite being the same model number (A1466).

According to the Mac Resource Inspector at the Apple Genius Bar, the logic board was overcharged. This made the fan run at a minimum of 6200 rpm and subsequently forced kernel_task to go insane.