Chosen Solution
I have replaced the original battery. The laptop booted as soon as I connected the power supply. I was able to log in and briefly, not extensively verify that my MacBook was operating properly. Knowing I had to charge the new battery to 100%, I shut down and left the Mac charging overnight. In the morning, the MagSafe light was solid green, suggesting that battery had charged . However, the laptop refused to boot, with or without the power connected. I reset SMC, which seems to be working by the blinking MagSafe green light. I disconnected the battery, reset power management, hoping to run off the power supply, all to no avail. I have read lots of similar questions on this forum but nothing seems to fit my case. I’m at my wit’s end.
Let’s give this a try, disconnect the battery again with nothing plugged in press and hold the power button for a good 15 secs. to allow the logic board to fully discharge. Now carefully plug in the MagSafe charger leaving the battery still disconnected. Press the power button did your system boot up? If it did, carefully shut it down properly.
