MacBook Pro charger blinks but doesn't charge

The MagSafe 3 connector manages charging through a sophisticated communication protocol (a "handshake") with the Mac's firmware. Since the battery has been left at zero for years, its voltage has dropped below the minimum safety threshold. As a result, the Mac's logic board won't boot, the communication fails, and the MagSafe goes into an error state (indicated by the blinking LED).

The USB-C/Thunderbolt ports on the M3 MacBook Pro, however, utilize the standard USB Power Delivery (USB-PD) protocol. This system allows the charger to send a tiny amount of current (a "trickle charge") directly to the battery management system, even if the computer is completely dead and lacking logical communication.

1. Disconnect the MagSafe cable and use a standard USB-C to USB-C cable connected directly to the Apple power brick.
2. Plug it into one of the Thunderbolt/USB-C ports on the Mac.
3. Leave it plugged in for at least 2 to 3 hours without touching it. Do not try to turn it on right away; the battery needs time to build up the minimum voltage required to "wake up" its safety circuits.

If you see the battery charging icon appear on the screen after a few hours, the problem is solved. Once the Mac turns on and reaches a small charge (e.g., 10-15%), you can unplug the USB-C cable and go back to using your MagSafe cable as usual.

Note: If the Mac shows no signs of life even after being plugged into USB-C overnight, it unfortunately means the battery's internal chemistry permanently degraded during those 3 years of inactivity. The battery's safety board will have locked it down permanently to prevent swelling, meaning a replacement at an authorized service provider will be the only option.

bassplayer12 wrote:

Hi all. Thanks for your feedback. The problem was something that I had suspected but could say for sure: faulty cable. Bought a new one and, voilà, problem solved. Thanks again.

If the battery has been left completely discharged for 3 years, then the battery has very likely suffered hardware damage.....many times battery swelling will occur. If the battery swells, then it can damage the Trackpad and cause the Bottom Case to bend & distort. Keep a close eye on it.

Lithium batteries need to always be stored with a charge somewhere between 20% to 60%. Keep in mind the battery will drain even while the laptop is powered off. Unfortunately even when the recent Apple laptops are powered off, many things can cause them to accidentally power on:

• Connecting or disconnecting any item including power
• Touching any key on the built-in keyboard
• Touching the Trackpad
• Opening the display even just the tiniest bit
• Faulty Lid Angle Sensor can cause laptop to power on if it thinks you are opening the display lid instead of closing it

Here is an Apple article with some details (relevant section is currently at the very bottom of the article) and mentions charging the laptop every six months.....I would recommend every three months as that is what one of my co-workers has been doing to ensure the battery charge level remains in the safe zone.

Batteries - Maximizing Performance - Apple

bassplayer12 wrote:

MacBook Pro (14-inch, M3 Pro or M3 Max, Nov 2023). The charger blinks but it doesn't charge at all. The laptop has seen almost no use in nearly 3 years. What could be the issue?

*MagSafe blinking Amber— If your MagSafe cable or power adapter isn't working

ref: If your MagSafe cable or power adapter isn't working - Apple Support

Unplug the power adapter from the wall, wait 60 seconds and then plug the adapter back in.

If your MagSafe cable or power adapter isn't working - Apple Support

Check the battery —search battery