Chosen Solution
I recently took out the (original) battery on my 2011 MacBook Pro with the intention of trying it in another similar model. However, I realised it was a slightly different year/different battery (2010). So, plugged the battery back in and now it’s showing 100% and only 5 cycles… except I know it’s at 0% and 500+ cycles. Also when the battery is plugged in the Mac will loop through starting up and will only start up properly and work fine… if the battery is disconnected. I’ve reset the SMC and even reinstalled the system (High Sierra). Is it time to give up on what (was) a perfectly OK battery? Any tricks I’ve missed? Thanks in advance.
Try unplugging the battery and mag-safe adapter. Press and hold the power on button for 10 seconds. Reconnect the battery and then the mag-safe. You should get a spontaneous re-boot. Are you using Coconut Battery to check it? https://coconut-flavour.com/coconutbatte… UPDATE Glad this solved your problem. Currently iFixit only has new batteries. I discourage using cheap knockoff batteries as they just don’t cut it. If you are looking for a used battery, most independent Mac techs have them, I know I do. Here’s the offering from iFixit: MacBook Pro 15" Unibody (Early 2011-Mid 2012) Battery
