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I recently installed a new battery in my early 2013 MBP 15" Retina. I put it through the recommended two complete charge/discharge cycles, and coconutBattery reports that the design capacity is 8460 mAh and the full charge capacity is 8942 mAh. (I think that's good.) The cycle count is now 7.

When the remaining charge reaches around 12%, the screen abruptly goes black. When I plug in the A/C adapter, I immediately hear the startup bong and the machine boots back up. I've looked for Console messages and haven't seen anything. And I have done the SMC reset.

The fact that it turns off without any warning suggests to me that the problem isn't simply miscalibration, but what do other people think? Should I just persist in this draining/charging routine a bit more?

Chap
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    You have failed/failing cells. See this relevant answer: https://apple.stackexchange.com/questions/236725/mid-2012-mbp-shuts-down-claiming-no-power-with-charge-at-30-or-40-or-more/238125#238125 – Allan Jun 18 '18 at 00:54
  • @Allan - What about those mAh numbers - aren't they an objective measurement of the amount of current in the battery (as opposed to percentages, which as the link points out, are extrapolated)? – Chap Jun 18 '18 at 01:15
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    afaik it's the amount of current the battery is able to produce. This could be calculated by measuring the voltage across the cells, or the amount of current going in vs out of the battery but we can't dip a stick in to measure the current left - it's stored as chemical potential. If a cell has failed it's possible there is a short between the battery positive and negative, which you could think of as a leak in the cell. – Scottmeup Jun 18 '18 at 02:11
  • Just confirming what @Scottmeup stated in his comment. The percentage is a calculated value as stated in the link I provided. – Allan Jun 18 '18 at 11:28
  • Well, live and learn, I guess. There seem to be no alternate explanations. I'm not going to try and fix it, so I can't be 100% certain that this is the correct answer, but it does sound likely. It's not like I wasn't warned ("Not User Serviceable"). – Chap Jun 18 '18 at 17:16

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