Electric vibration/shock while charging Mac

Definitely not normal. Best advice is to take it to an Apple Store or authorized Apple service provider for examination.

Of course you could try a different charger first to see if the trouble remains. Then you would know for sure which is causing the problem.

Lawrence Finch wrote:

IdrisSeabright wrote:

Generally, it's more dangerous than annoying.

Stop! Reverse That! It’s more annoying than dangerous!

It’s the result of energy picked up by the power cord if the cord is near an unshielded electrical cable in the wall. It is too low a current to be harmful.

Thank you! Yes, that's what I meant. Not enough coffee, too much coffee. Or I need a nap.

The standard two-prong AC plug adapter input for a MacBook Pro power adapter does NOT carry earth ground through to the power adapter electronics. . IF there is a mis-wire in your home, or the electricity being supplied is especially "noisy", that noise may get coupled through to your computer, and be felt as tingling when there is high consumption, such as when actively charging.

In the VAST majority of cases, the stray current is exceptionally small, and is not a cause for health concerns.

Because the nominal voltage supplied down the cable to the MagSafe or USB-C to the computer is around 20 Volts DC, it is generally not considered harmful to you in any way.

This is a picture of the AC extension cord setup that HWTech is referring to, and has been the same for many generations of Mac Power adapters:

Try a different outlet. It sounds like a grounding issue. While not common, it's also not a rare problem. Generally, it's more dangerous than annoying.

IdrisSeabright wrote:

Generally, it's more dangerous than annoying.

Stop! Reverse That! It’s more annoying than dangerous!

It’s the result of energy picked up by the power cord if the cord is near an unshielded electrical cable in the wall. It is too low a current to be harmful.

If it is a grounding issue as mentioned by @IdrisSeabright, then you can try using the Apple Power Adapter Extension Cable which has a third pin for ground....assuming your region supports such a cable. Here is a link to the cable for the US (change the region to see if one is available in your region):

Power Adapter Extension Cable - Apple

If this resolves the issue, then you may want to have an electrician examine the home wiring since something is not quite right there.

Also, if you have other external devices connected which have their own power supplies, you may want to disconnect them to see if that makes a difference. Sometimes if those devices have a problem, or if they are connected to a different electrical circuit, you can have some issues as well.

In the rest of the world that Apple adapter has 3 pins, it’s only in the US that it is 2 pins. However, that doesn’t really matter, because neither side of the power into the computer is ground; both are “floating”.

If you’re inclined to check for problems with the outlet wiring, outlet testers are available.

I use one of these, but there are cheaper options available:

https://www.kleintools.com/catalog/electrical-testers/gfci-receptacle-tester-lcd

I verified that the extension cable (we own 4-5 of them) does have a ground contact. It is hard to see but it makes contact with the metal stud that holds the adapter in place. Here's a close-up:

⚠️ However, the age of a house can be at play, and only a licensed electrician can confirm that. A friend bought an older home in the historic district. It had a complete remodel and restoration including, per the sales sheet, "all new electrical."

After having issues like you report, they had an electician check. He found that "all new" only applied to the outlets, which were new, three-prong U.S. pattern. The electrician found most never had their ground wires connected. Oops

Lawrence Finch wrote:

In the rest of the world that Apple adapter has 3 pins, it’s only in the US that it is 2 pins. However, that doesn’t really matter, because neither side of the power into the computer is ground; both are “floating”.

I am not sure I agree that "only the US" does not use grounded adapters by default. The UK does appears to use three prong adapter. But if you look at the Apple world traveler adapter kit sold in the US, most are two-pin:

If in doubt, let Apple examine the computer.

Generally speaking, a tingling sensation is not unusual for certain computers and other double-insulated devices with a metal enclosure, where a two-prong non-grounded/non-earthed mains connection is used. This effect may be more prominent in countries/areas with 230-240 V AC mains voltage.

Someone with the necessary expertise could find out more by using a digital multimeter. Do NOT connect the multimeter to the mains (wall outlet/socket). With a multimeter set to the highest AC voltage range, one test probe would merely touch the computer's metal enclosure and the other probe a grounded/earthed object (such as a kitchen sink). The multimeter may show a voltage anywhere from a few volts to something like 100 V AC or more (at least in a 230-240 V AC country).

However, a digital multimeter has a high input impedance, so readings may be unrealistic unless an appropriate load is used. From a safety perspective, the resulting current is an important factor. An old article Does a "tingle" mean your appliance is dangerous by Jim Rowe in Electronics Australia, August 1988 had more about this. Newer standards/reports/articles may provide additional information.

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