Chosen Solution
My MacBook Pro will only run when plugged in. The battery was old, so I replaced it, but that didn’t seem to make any difference. It says that the battery is charged to 97 or 98 percent on the screen and the lights on the battery all light up when I push the tester button. Power cord, i/o board, and hard drive are all new within the last year. What should I try?
Try resetting the SMC Apple’s TN on resetting the SMC just to make sure. Otherwise, I’m sorry to say your system has the power transistors which control switching between the AC/battery power on the main logic board which would mean it would need to be repaired or replaced.
