Not sure if this works on newer models, but it does on 2007-08 models. Here’s the backstory. Got my hands on an 07 that wouldn’t turn on. Tried the SMC reset (remove power, battery, hold power for 10 seconds); no dice. Then I found this lovely gem … remove the battery, remove the AC, hold power for 10 seconds … WHILE STILL HOLDING POWER reconnect the AC and continue to hold power for 10 seconds. Release and press power again. This seems to bypass the charging system. The fans run at full tilt and if the machine loses power you have to do it again but it does come up. In my case I think this is due to a crappy 3rd party battery + charger but it’s getting me through until I can do more work.