Dangerous Voltage from a MacBook Pro?

[iRun26.2]

I have been comparing the 2020 13.3" MacBook Pro to a 2019 16" MacBook Pro. I have them side by side and with the 13.3" hooked up to to my LG 32" 4K (32UD99) monitor (via the USB-C cable that came with the monitor). The 16" is powered by the USB cable/white box it came with. Both power adapters go to the same power strip.

I noticed a tingling sensation when I put my left hand on one computer and brushed my right hand on my other computer. I got out my newly purchased multi-meter (for electronics work for my job at home) and first determined that the "space grey" coating on both computers does not conduct. Next, I added a USB peripheral to each computer such that the ground of each computer would be accessable.

I found an AC potential of slightly over 50V between the two computers!

Now I don't think one could get electrocuted by a 50V AC potential... but still, something doesn't seem right! What could be going on?!

 

[DeltaMac]

If you get "a tingling sensation when" you touch one computer, and brush your hand on your other computer, and also say the cases don't conduct current, then you are mis-interpreting the data. How can the case "not conduct", yet you can touch both cases, and feel a mild sensation. (The anodized coating would still conduct, if there is a problem with a ground somewhere)
Do you get the same "feeling" if you use only the power adapters that each came with, and no other external devices attached to both MBPros?

 

[Allyance]

What I think you are experiencing is a voltage leak on one power supply. Do both power supplies have 3 prong grounded plugs? Probably only one. It's not the voltage that would harm you, but high current as well. Since it is between two ground systems, I doubt ther is any current flow.

 

[ScreenSavers]

It has to do with the grounding of the device it is connected to. It happens to me in my office a lot if I touch my Mac Pro desktop and something else metal connected to the same outlet. (Cyberpower UPS.)

 

[jerryk]

Sounds like a ground problem. It is a common issue. Get a grounded cable for your MBP's charger and see if the problem disappears.

You may have one if you had previous MacBooks. The cable has not changed in a long time and used to be included with every MacBook. If not, here is the link.

Power Adapter Extension Cable - Apple

Apple Store Search Results

www.apple.com

 

[iRun26.2]

If you get "a tingling sensation when" you touch one computer, and brush your hand on your other computer, and also say the cases don't conduct current, then you are mis-interpreting the data. How can the case "not conduct", yet you can touch both cases, and feel a mild sensation. (The anodized coating would still conduct, if there is a problem with a ground somewhere)
Do you get the same "feeling" if you use only the power adapters that each came with, and no other external devices attached to both MBPros?

Just because you don't understand it / can't explain it doesn't automatically disqualify my ability to make measurements and observations. There is no question that the 'space grey' coating does not conduct. I know how to use my multi-meter. As a verification, I measured the conductivity on my original MacBook Air (pure aluminum) and it's surface does conduct as would be expected.

The feeling I get is not detected by merely putting hand on one computer and the other hand on the second computer. I must move the hand to pick up the tingling. Maybe you wouldn't notice it but I do. It doesn't happen when the computer powered by the power-supply (and not the monitor) is running on batteries.

My explanation (which is just a guess as to why I'm feeling something) is that the 'space grey' coating acts as a dielectric to the bare aluminum below and my hands and body complete the circuit to the other computer via a similar dielectric. The small bits of electricity that may flow I am able to feel when I move my hand.

Why it is happening is the another question (which I want to find the answer for because it makes me nervous using my current setup). I'll be testing the two computers on their own power supplies shortly.

 

[Ma2k5]

Just because you don't understand it / can't explain it doesn't automatically disqualify my ability to make measurements and observations. There is no question that the 'space grey' coating does not conduct. I know how to use my multi-meter. As a verification, I measured the conductivity on my original MacBook Air (pure aluminum) and it's surface does conduct as would be expected.

The feeling I get is not detected by merely putting hand on one computer and the other hand on the second computer. I must move the hand to pick up the tingling. Maybe you wouldn't notice it but I do. It doesn't happen when the computer powered by the power-supply (and not the monitor) is running on batteries.

My explanation (which is just a guess as to why I'm feeling something) is that the 'space grey' coating acts as a dielectric to the bare aluminum below and my hands and body complete the circuit to the other computer via a similar dielectric. The small bits of electricity that may flow I am able to feel when I move my hand.

Why it is happening is the another question (which I want to find the answer for because it makes me nervous using my current setup). I'll be testing the two computers on their own power supplies shortly.

Nothing to do with coating, I was able to replicate it on both silver/SG MBP’s. As others said, it’s a grounding issue which became more prominent when Apple stopped supplying the extension cable to their power adapters. When used with the extension lead, it used to stop, but as soon as I didn’t use it I got a tingling sensation while it used to charge.

 

[Appledoesnotlisten]

Sounds like a ground problem. It is a common issue. Get a grounded cable for your MBP's charger and see if the problem disappears.

You may have one if you had previous MacBooks. The cable has not changed in a long time and used to be included with every MacBook. If not, here is the link.

Power Adapter Extension Cable - Apple

Apple Store Search Results

www.apple.com

Do you know how we can ground the 2016+ models that have only two prong chargers?

 

[iRun26.2]

What I think you are experiencing is a voltage leak on one power supply. Do both power supplies have 3 prong grounded plugs? Probably only one. It's not the voltage that would harm you, but high current as well. Since it is between two ground systems, I doubt ther is any current flow.

The power supply to the 4K display is the only one that has a three-prong outlet connector. The MacBook Pros come only with a two-prong outlet connector.

 

[Ma2k5]

Do you know how we can ground the 2016+ models that have only two prong chargers?

This will solve it.

Power Adapter Extension Cable - Apple

Apple Store Search Results

www.apple.com

 

[jerryk]

Do you know how we can ground the 2016+ models that have only two prong chargers?

Yes. If you look at your charger, the 2 pronged part can be slide off the charger and replaced with the cable I posted.

Like I said, they used to ship the charger with the 2 prong that you have installed on the charger, AND the cable that gave you a 5 foot extension and the 3 prong grounded plug. I guess they determined that most people never used the 3 prong grounded extension cable and decided to not ship them.

 

[iRun26.2]

Yes. If you look at your charger, the 2 pronged part can be slide off the charger and replaced with the cable I posted.

Like I said, they used to ship the charger with the 2 prong that you have installed on the charger, AND the cable that gave you a 5 foot extension and the 3 prong grounded plug. I guess they determined that most people never used the 3 prong grounded extension cable and decided to not ship them.

So, it must not be very dangerous, then. It kind of scared me when I could measure 50VAC between the grounds of the two computers. If I accidentally shorted them out it wouldn't hurt the computers, would it? I don't plan to do that! Maybe that is exactly what the three prong connector (that came with previous MacBooks) actually does (harmlessly)?

 

[jerryk]

So, it must not be very dangerous, then. It kind of scared me when I could measure 50VAC between the grounds of the two computers. If I accidentally shorted them out it wouldn't hurt the computers, would it? I don't plan to do that! Maybe that is exactly what the three prong connector (that came with previous MacBooks) actually does (harmlessly)?

The issue of tingling is caused by coils and other devices in the systems. If one wants they can watch this video that does a good job going into detail about this and how the current levels are extremely low and non hazardous (see 3:00). It also goes into how a grounded plug (3 pin in USA) eliminates the issue.

Also, this is not new or unique to Apple. Here is a link to a Dell reply on the issues about this they were seeing back in 2007. https://blog.dell.com/en-us/notebook-tingle-sensation-what-39-s-going-on/

 

[biffuz]

This has been discussed several times, using a grounded power cable (on a grounded outlet) removes the effect. I can reproduce it 100% of the times.

 

[iRun26.2]

The issue of tingling is caused by coils and other devices in the systems. If one wants they can watch this video that does a good job going into detail about this and how the current levels are extremely low and non hazardous (see 3:00). It also goes into how a grounded plug (3 pin in USA) eliminates the issue.

Also, this is not new or unique to Apple. Here is a link to a Dell reply on the issues about this they were seeing back in 2007. https://blog.dell.com/en-us/notebook-tingle-sensation-what-39-s-going-on/

My grounded extension plug arrived today and the problem went away. Thank you. I'm glad it wasn't a dangerous problem after all.

I wish all MacBooks came with them like they used to. I had one from my original MacBook Air but I could not find it so I ordered another one.

 

[maerz001]

Just because you don't understand it / can't explain it doesn't automatically disqualify my ability to make measurements and observations. There is no question that the 'space grey' coating does not conduct. I know how to use my multi-meter. As a verification, I measured the conductivity on my original MacBook Air (pure aluminum) and it's surface does conduct as would be expected.

The feeling I get is not detected by merely putting hand on one computer and the other hand on the second computer. I must move the hand to pick up the tingling. Maybe you wouldn't notice it but I do. It doesn't happen when the computer powered by the power-supply (and not the monitor) is running on batteries.

My explanation (which is just a guess as to why I'm feeling something) is that the 'space grey' coating acts as a dielectric to the bare aluminum below and my hands and body complete the circuit to the other computer via a similar dielectric. The small bits of electricity that may flow I am able to feel when I move my hand.

Why it is happening is the another question (which I want to find the answer for because it makes me nervous using my current setup). I'll be testing the two computers on their own power supplies shortly.

There where a couple of threads already regarding the issue and solved by the extension cable. Just use the search function.

Btw: There is no Macbook with “pure aluminium”. Unless you grinded it
All are anodized surfaces. The silver ones just have a transparent coating...

pure aluminium would corrode in a heartbeat with sweat from fingers.