When you plug your MacBook’s power adapter in and its light turns amber, your system’s battery should charge; however, there may be times when this does not occur, and upon clicking the Battery menu you will see a notice that says “Battery Not Charging.” Despite this, the system will work fine as long as the power is plugged in, but if you disconnect power then the battery will progressively drain.
With batteries and other power management issues, there really isn’t much you can do, but if this happens, there are a few general approaches you can try for fixing the issue:
1. Reset your power adapter
First be sure the power adapter is showing a green or amber light, which indicates it is working as expected. If you see no light at all then the device might not be working properly. Regardless, first unplug the adapter from the wall and allow it to sit for about a minute to reset, then try plugging it back in.
If you have another power adapter handy, then try using it instead. Even if your MacBook’s power adapter is the larger 85-watt version, you can still use a 60-watt or 45-watt adapter, provided it has a compatible MagSafe connector. The difference is the time it will take to charge the system, and if the power demands of the system are greater than the wattage the adapter can provide, then the system will switch to using the battery. To avoid this when testing with a smaller adapter, quit all apps and dim the display to reduce power draw as much as possible.
3. Restart your Mac
A quick restart will refresh your Mac’s power settings and configurations, and may be all that’s needed to kick your battery into gear again. However, it is a bit of an interruption to your workflow so try the first two options.
4. Reset the SMC
If a basic restart does not work, then power the system down and reset your Mac’s system management controller (SMC). Doing so should refresh hardware-level settings for power management. To reset the SMC, turn off your MacBook, plug in the power adapter, then hold the Shift-Control-Option keys on the left-hand side of your keyboard, and then press the power key along with the others. Release the keys, and then press the Power key to start your system up.
5. Reboot your Mac to Recovery mode
While power errors are generally lower level problems, you may have some OS configuration issue that is causing the problem. To test this, you can try booting your Mac to Recovery mode by restarting and holding Command-R when you hear the boot chimes. If you can see your battery charging in this mode, but it still has problems when booting to your main OS, then you may need to remove third-party plugins, extensions, and other add-ons you have installed, or reinstall OS X.
Finally, if none of these approaches address the problem and your Mac continues to refuse to charge your battery, then you will likely need to take your system in to an Apple service provider for servicing.
You missed the most obvious reason.
Visually inspect the MagSafe port on the computer. Since they hold in the power plug via a magnetic connection, they are also susceptible to sucking in other little bits of metal and interfering with a good connection.
Use an old toothbrush, or toothpick, or tweezers to remove any debris inside the port.
I just had this happen to me. In fact, the MagSafe light would go off mid charge.
It was the charger on my 6-year-old MBP. I know that virtually all power-supplies weaken over time, so I tried a different Apple 85W power adapter… and that solved the problem!