How do I fix "Battery is not charging" for 2012 macbook pro retina?

Solution 1:

Troubleshooting is a process of elimination and often requires patience.

In this situation, if you've already reset the SMC (and it may be worth doing again, ensuring you've followed the correct steps for your model), you'd normally want to isolate the different components by testing them separately (e.g. testing the battery in another 2012 MBP, testing the AC charger with another MBP, and so on).

Of course, when you're trying to do things yourself, that isn't so easy.

Even though you've reset the SMC, I'd do that again first and ensure you refer to How to reset the System Management Controller (SMC) on your Mac on Apple's website. Read through this page carefully as the instructions differ for different models of Mac.

Once you've done that, and assuming it has no effect, you'd want to run Apple Hardware Test.

Run Apple Hardware Test

Your model MBP uses Apple Hardware Test. To use this, follow these steps:

1. Shut down your MacBook Pro
2. Restart your MacBook Pro
3. Press and hold the D key before the gray startup screen appears.
4. After a while, Apple Hardware Test (AHT) will start.
5. When prompted, select your language and click the right arrow.
6. When the AHT console appears, you can choose to run Basic tests by clicking the Test button. However, I suggest you select the "Perform extended testing" checkbox before you click the Test button.
7. Your test results will appear in the window in the bottom-right of the console.

Note 1: that the extended test will take some time. Take a note of the results and report back.

Note 2: If pressing and holding the D key at Step 3 doesn't work, start again at Step 1 and, at Step 3 press and hold both the OptionD keys instead. This will try and run diagnostics from the internet instead, so you will need to allow more time for it to complete.

Once you've done that, let me know what happens.

Your battery

Based on your question, your battery has only done 27 cycles, so I'm assuming you've only recently bought this battery. If so, I would be speaking to Apple (or the 3rd party vendor) from whom you bought the battery as it is possible it's an EEOL (Early End Of Life) situation. Any reputable retailer will be willing to test/replace the battery in this situation.

Solution 2:

You haven't tried checking the power adapter. Power adapters get damaged so before being concerned about the battery. It's best to check wether the power cable is working by either plugging it into another similar MacBook Pro(make sure it's the exact model) or by reaching Apple.

Solution 3:

I would suspect something is wrong with the center pin of either your MacBook or your power adapter. In this Apple support document it is described that a missing contact on the center pin may cause the adapter not to charge the computer. This answer elaborates on the pin configuration that is necessary to charge the computer further.

As the Apple support document states, I suggest you closely inspect the pins on your adapter and the contacts on your MacBook.

Please only proceed if you have the necessary technical expertise:

As a next step you may want to measure if there is a current on the center pin. This website explains in more detail how Magsafe works. Charging is basically negotiated between the adapter and the computer.

When the Magsafe connector is plugged into a Mac, a lot more happens than you might expect. I believe the following steps take place:

1. The charger provides a very low current (about 100 µA) 6 volt signal on the power pins (3 volts for Magsafe 2).
2. When the Magsafe connector is plugged into the Mac, the Mac applies a resistive load (e.g. 39.41KΩ), pulling the power input low to about 1.7 volts.
3. The charger detects the power input has been pulled low, but not too low. (A short or a significant load will not enable the charger.) After exactly one second, the charger switches to full voltage (14.85 to 20 volts depending on model and wattage). There's a 16-bit microprocessor inside the charger to control this and other charger functions.
4. The Mac detects the full voltage on the power input and reads the charger ID using the 1-Wire protocol.
5. If the Mac is happy with the charger ID, it switches the power input to the internal power conversion circuit and starts using the input power. The Mac switches on the appropriate LED on the connector using the 1-Wire protocol.

This process explains why there is a delay of a second after you connect the charger before the light turns on and the computer indicates the battery is charging. It also explains why if you measure the charger output with a voltmeter, you don't find much voltage.

The complex sequence of steps provides more safety than a typical charger. Because the charger is providing extremeley low current at first, there is less risk of shorting something out while attaching the connector. Since the charger waits a full second before powering up, the Magsafe connector is likely to be firmly attached by the time full power is applied. The safety feature are not foolproof, though, as the burnt-up connector I tore apart shows.

Don't try this at home

Warning: I recommend you don't try any of these experiments. 85 watts is enough to do lots of damage: blow out your Mac's DC input board, send flames out of a component, blow fuses, or vaporize PC traces, and that's just the things I've had happen to me. The Mac and charger both have various protection mechanisms, but they won't take care of everything. Poking at your charger while it's plugged in is a high-risk activity.