MacOS underestimates battery life on replacement battery I recently replaced the battery in my late 2011 MacBook Pro, and the battery seems to do fine except that it will drop very quickly from about 75% down to 2% and then continue to work for quite a while (I haven't timed it but probably close to an hour if not more of normal use).

What could cause this, and how might I fix it, so that it shows a more reasonable battery life estimate?

It's a little irritating having to guess at how much time I have left before it sleeps.



coconutBattery says:


Current Charge: 114 mAh (2%)


Note: this hasn't changed from 114 in the 15 (edit: 20) or so minutes since I first checked.


Full Charge Capacity: 5752 mAh
Design Capacity: 6900 mAh
Manufacture date: 2015-06-24
Loadcycles: 13
macOS Battery status: Good
Discharging with: 12.15 Watts
Manufacturer: Simplo
Battery failure: Yes


That last one makes me a little nervous. What does "Battery failure: Yes" mean?
I'd do a NVRAM and SMC reset (in that order). Before following the steps below, ensure you have no external hardware connected and that you're using the built-in keyboard.

Reset the NVRAM

Reset the NVRAM on your MBP as follows:


Shut down your machine. That is, a full shut down, not just logging out.
Press the power button and then press the commandoptionpr keys. You have to make sure you press these keys before the gray screen appears or it won’t work.
Hold those keys down until your MBP reboots again and you here the startup chime.
Let go of the keys and let your MBP reboot normally.


Note: When you log back in you may need to readjust some of your system preferences (e.g. speaker volume, screen resolution, startup disk selection, time zone information, etc).

Reset the SMC

There's a couple of ways you can reset the SMC on your MBP, however I prefer the following steps:


Shut down your MBP
Keep the power cable plugged in
Press at the same time shiftoptioncontrol (on the left side of the keyboard) and the power button
Let go
Turn your computer back on with the power button


After resetting both the NVRAM and SMC, use your computer to determine how well macOS is reporting the remaining battery life.

Battery Condition

To view what macOS has determined as the battery's condition, hold down the Option key and click on the battery icon in the menu bar. You'll now see the condition reported at the top of the drop-down menu that appears.

coconutBattery

If you haven't already, I recommend you download and install coconutBattery 1. It provides a whole heap of information that you'll find useful!

1 Note: I am not affiliated with coconutBattery in any way.