A lot of MacBook user report a certain voltage phenomenon. The same happened to me with a MacBook 12” early 2016) and a MacBook Pro 13” (early 2020). Plugging in, it feels like current or voltage is going through your hand or fingers while touching the MacBook, especially left or right beside the Trackpad. It feels like micro-vibrations. It is not a buzzing you hear, you feel it with you run your fingers through the metal case.
The ‘vibration’ as some call it, or ‘tingling sensation in the fingers’ as other call it (while charging) is not harmful to your Mac or to you. Some users find it alarming or inconvenient.
The origin of the micro-vibration of MacBooks
This ‘micro-vibrations’ are generated due to a lack of sufficient electrical grounding of the MacBook. The power adapters does not have an additional electrical grounding line.
This is a normal consequence of how the power adapter is designed. There is no direct electrical connection between the power mains and the low voltage laptop side of the adapter. They are completely isolated from each other by isolated power inductors operating like an isolation transformer. That means there is no direct electrical connection between the AC outlet ground and the laptop chassis ground. They are separated.
This is particularly common complaint for MacBooks because of their metal case. Other laptops with a plastic case usually don’t have the problem. I asked a lot of my Apple friends and all (!) reported these micro-vibrations. Some of them thought that it’s “normal” for MacBooks! Somebody told me that his 12 year old MacBook Pro got this electrical issue, too. This means it is an permanent problem of all MacBooks, MacBook Airs and MacBook Pros. This electrical grounding effect is more or less also impacted by the country standard voltage and your personal office set up (wearing shoes, having a carpet or not…).
Depending on the design standard, this leakage current is limited to two or three hundred microamps. This is not enough to be dangerous, most people can’t even feel it, but it can cause slight tingling in certain circumstances, especially if you body has a good connection to earth ground.
So what it boils down to is a design trade off between leakage current and EMI noise suppression. In order to reduce the amount of EMI, there exists a tiny amount of leakage current through the filter capacitor. Verifying that the leakage current is a safe level is part of the certification testing for the power adapter.
The solution for eliminating micro-vibration of MacBooks
Mac laptops have historically been shipped with both an ungrounded two prong plug and a grounded three prong extension cable for the power adapter, and “the tingle” was something that was usually resolved by using the grounded (three prong) extension cable with the power adapter. However, I understand that Apple is no longer shipping the three prong extension cable with some machines, which is bizarre and churlish, but there it is. You can buy a grounded plug off of Amazon, although if you’re plugging into an ungrounded outlet or one with a “fake” ground, it won’t make any difference.
Get a cable to connect the power brick with the electrical socket. It has three pins. It grounds the power brick and it grounds the Macbook. No more “buzzing”.
Based on my experience, I think it’s unlikely that if you exchange the machine you will get one that does not demonstrate this unfortunate artifact of a metal case with an ungrounded power supply. I suggest to try the grounded extension cable first if you haven’t already.
Here’s How To Fix MacBook Micro-Vibrations While Charging Due To Insufficient Grounding
- Buy a power adapter cable with a plug with 3 pins (one for electrical grounding). It is called Apple Power Adapter Extension Cable (for MacBook, MacBoo Pro, MacBook Air, Amazon number B00VU31O7Y for US, watch out for the correct plug for your country!):
- Change the original 2-pin plug with the Apple Power Adapter Extension cable,
- Put your fingers left and right beside the Trackpad. The micro-vibrations are gone.
- For success validation, redo the substitution: The micro-vibrations are back!
A lack of sufficient electrical grounding of MacBooks with a metal housing leads to micro-vibrations left and right beside the Trackpad. The fix is to take a grounded power adapter with three pins / lines.
Stay tuned! 😉