MBP 15" early 2011 shuts down after login without power cord Update #1:


  I uninstalled gfxcardstatus. Now the only times it shuts down instantly
  are when I initially log in (tried on user with Filevault and one
  without), and when I log out from one user and log into another.  I've unplugged while logged in, I've put it to sleep and
  come back, I've logged out and back in (as same user), and it stays on. It always
  shuts down if I log in from a fresh reboot.


I've seen issues where the MBP shuts down after login, and where the MBA shuts down without power, but this is just a little different.

The computer works fine when plugged in. No issues. The problem comes up when it's unplugged. This started just after I updated to 10.10.4, although I don't know whether it's related.


Start computer with or without battery, get to login screen.
Can maintain this state for minutes at a time plugged in or on battery on login screen.
When I log in, the computer's immediate action is to shut down. Screen just goes dark -- no warnings, no nothing.


Any ideas? SMC reset did not help. Magsafe light looks yellow or green as is appropriate to charging situation. No other weird behaviors or warning signs.

System information -> power shows nothing weird:

Charge Information:
Charge Remaining (mAh):   5955
Fully Charged:    No
Charging: Yes
Full Charge Capacity (mAh):   6547
Health Information:
Cycle Count:  143
Condition:    Normal
Battery Installed:    Yes
Amperage (mA):    1337
Voltage (mV): 12468


I get no notification of any kind after it starts again as is described by this question.
It might be your GPU.  Try going to System Preferences->Energy Saver and changing the "Graphics" setting.  If it was on "Better battery life" then set it to "Higher performance", and vice-versa if it already was on "Higher performance".