Power brick extension cable (2-prong)

[MacInWin]

The apple power "brick" for the MBP comes with various extension cables, depending on the country. In the US, it has a three prong plug on it. But if you don't use the cable, the adapter only has two prongs, and they are NOT even polarized. So, from that configuration, it would appear that the brick itself can use either two or three and that if it's two, it doesn't care which is hot and which is neutral.

What I am looking for is a two prong US Extension cable. My car has a built in inverter, so I could power my MBP except that where it is the brick won't plug in directly securely. But the inverter outlet is two-prongs only, so the three-prong cable doesn't work. I could get a three to two converter, but a cleaner option is a two-prong extension cable.

Anybody got any ideas where one might be obtained? I searched the internet a bit, but all I could find were three pronged.

TIA,

EDIT: My MBP does not use USB-C, so even though those are available, what I need is the cable for my brick so that I can use the MagSafe connector on the mid-2015 MBP.

 

[Lifeisabeach]

I doubt they exist. Some brief googling didn't turn any up. You could just use a pair of pliers to forcibly remove the ground prong, but a better solution would be to use a "three-prong to two-prong" adapter.

EDIT: I linked to one that has a little metal piece sticking out below where the ground prong would be, but that may not be what you should be using in your car since that metal piece basically replaces the prong and grounds to the screw in a wall outlet, if I'm not mistaken. Instead, look for something like this:

https://www.amazon.com/dp/B07YRKSSRN/?tag=macforums0e4-20

 

[Lifeisabeach]

Actually, you know what? You can take a figure 8 power cord, like what the Mac mini comes with for example, and simply plug that into the brick! The little plug that comes with the brick has a standard figure 8 connector. I just tested it with a figure 8 cable I have and it slides right in.

EDIT: found a page demonstrating this.

Mac Laptop Power Cord Tip – Cool Tools

kk.org

 

[MacInWin]

That is an ingenious solution! I happen to have a spare figure 8 cable that I will give a try.

 

[pm-r]

What I am looking for is a two prong US Extension cable.

Maybe I am Not understanding something, but why not forget using the Extension cable that comes with the adapter, and just use an ordinary two connector extension cable and the two prongs of the adapter???

I cannot see why that would not work, but I do not know if the MBPro will work off the normal square power source that most inverters produce.


- Patrick
=======

 

[MacInWin]

That would work, Patrick, and I had used that for a while, but prefer a dedicated cord. Most of the two prong extension cords I could find were pretty small and I don't know how they would carry the load. The figure 8 cords are heavier and I feel a bit safer using them.

 

[krs]

I researched this a while back - Why does Apple use a grounded extension cord with their power adapters if the ground is non-functional?
There are a number of reasons people have posted on line - none of them make any sense.
Some of my family have just pulled off the ground pin on the three prong plug - which is probably illegal.
I replaced the three-prong plug with a CSA/UL approved two-prong plug on one extension cable to make the able the OP is looking for, but that may be illegal as well even though there is no safety issue.

 

[Lifeisabeach]

I researched this a while back - Why does Apple use a grounded extension cord with their power adapters if the ground is non-functional?
There are a number of reasons people have posted on line - none of them make any sense.
Some of my family have just pulled off the ground pin on the three prong plug - which is probably illegal.
I replaced the three-prong plug with a CSA/UL approved two-prong plug on one extension cable to make the able the OP is looking for, but that may be illegal as well even though there is no safety issue.

I was wondering that myself. My thought was that maybe that round metal piece that the adapter slides onto doubles as the ground. I don't have a cord that plugs into the charger brick (the new MBA doesn't come with it... cheap ********!) so i can't take a look inside the slot to see if there's a metal plate that would make contact with the round button.

EDIT: hey, I was right!

iPad charger teardown: inside Apple's charger and a risky phony

This article is now available in Turkish iPad şarjının iç yapısı and Chinese [中文翻译版本] Apple iPad原装充电器拆解 . Apple sells their iPad charger...

www.righto.com

How to properly ground a MacBook Pro

I have a MacBook Pro 4.1. In the past - from time to time - you could feel a bit of electricity close to the aluminium case when working in AC mode, but now things are getting worse. I can feel the

apple.stackexchange.com

 

[MacInWin]

My thought was that maybe that round metal piece that the adapter slides onto doubles as the ground.

The strangeness is that with the non-extension adapter on the brick there are only TWO prongs, so if you plug it into a three socket outlet, the ground socket has nothing in it. The little adapter is just plastic with two prongs connected to the figure 8 connector, nothing to the round metal piece. But if you attach the extension cord, there are THREE prongs, with two connectors at the end that connects to the brick and there are metal sides in the slot where the extension cord attaches to the brick, which is connected to the ground prong on the extension cord. So, Apple apparently thinks the if you plug the brick directly to the mains outlet, you don't need that ground, but if you use the extension cord you do? I'm stuck for finding any logic in that design.

 

[Lifeisabeach]

The strangeness is that with the non-extension adapter on the brick there are only TWO prongs, so if you plug it into a three socket outlet, the ground socket has nothing in it. The little adapter is just plastic with two prongs connected to the figure 8 connector, nothing to the round metal piece. But if you attach the extension cord, there are THREE prongs, with two connectors at the end that connects to the brick and there are metal sides in the slot where the extension cord attaches to the brick, which is connected to the ground prong on the extension cord. So, Apple apparently thinks the if you plug the brick directly to the mains outlet, you don't need that ground, but if you use the extension cord you do? I'm stuck for finding any logic in that design.

I can only assume it's the convenience of being able to fold the prongs down on the squarish plug. Probably more difficult to do with that third one. Also, it provides an option for folks who need to use it with a two-prong outlet, like in your case if not for it being too bulky otherwise. I'm not sure if having a ground is beneficial when using a surge protector either.

 

[MacInWin]

I can only assume it's the convenience of being able to fold the prongs down on the squarish plug. Probably more difficult to do with that third one. Also, it provides an option for folks who need to use it with a two-prong outlet, like in your case if not for it being too bulky otherwise. I'm not sure if having a ground is beneficial when using a surge protector either.

Maybe, but in other countries, with other standards, that short adapter doesn't fold. In fact, there isn't really any real need for it to fold, you could have a three prong short adapter and just remove it to throw in your computer bag along with the brick and cable, if you wanted to. Or leave it attached and just go with it.

I've travelled with my MBP, and in UK, for example, with the large three prong sockets I use an adapter that just converts to a standard US three prong outlet with no power changes, and the brick can be plugged into that 240ac just fine, but the short adapter you get with a Mac in the UK has the big three prongs, non-folding.

I'm betting Jony Ive just didn't like the look of the prongs sticking out of the brick in the photos for the thing and so the two standards. No engineering sense, just aesthetics. And I'm ok with that, but then why the three prongs on the extension cable? Just for show?

 

[pm-r]

The figure 8 cords are heavier and I feel a bit safer using them.

I would think that most cords of that type, whether dedicated or extension type, would probably be made up of 18AWG wire that should easily carry any loads that you are working with, but the insulated covering might be heavier on some cords and appears that they use a heavier wire.


- Patrick
=======

 

[krs]

What struck me about the link in post #8 that people who used the two-prong arrangement actually felt some leakage current which the use of the grounded extension cord eliminated. This seemed to be an issue with 240 volt supplies only and maybe with Macs sold outside of North America.
I (or family) must have owned two dozen different MacBooks of all types with metal cases that were used with duckheads an I don't recall anyone ever complaining about a 'tingle' or anything along those lines when used in Canada or the US or even in Europe, Asia or Australia with the simple mechanical adapters.

 

[Lifeisabeach]

I'm betting Jony Ive just didn't like the look of the prongs sticking out of the brick in the photos for the thing and so the two standards. No engineering sense, just aesthetics. And I'm ok with that, but then why the three prongs on the extension cable? Just for show?

The third prong on the extension cable is the ground pin. Something I would consider essential at least if not using a surge protector. The second link from my prior post best explains how Apple engineered it.

 

[krs]

And I'm ok with that, but then why the three prongs on the extension cable? Just for show?

One comment I had read about that a while back is that a three prong plug provides a more solid physical connection at the receptacle than the rather flimsy North American two prong plug.
That makes a bit of sense. On two prong plugs one sometimes has to bend the prongs slightly to get a solid mechanical connection.

 

[krs]

The third prong on the extension cable is the ground pin. Something I would consider essential at least if not using a surge protector.

Depends if the device is considered double-insulated or not.

 

[MacInWin]

The third prong on the extension cable is the ground pin. Something I would consider essential at least if not using a surge protector. The second link from my prior post best explains how Apple engineered it.

I read that, but that article is almost 10 years old. The power supply inside the brick isolates the Mac from the power source, so the grounding functions should not be any part of the alleged voltage on the case. The system is UL approved, so the Underwriters Lab has tested the safety of the design and units and found them in compliance.

In the two prong outlets, one of the two is "hot" and the other "neutral." Neutral is the cold side, with no power on it. Switches should always go in the "hot" side to cut off power, not cut off the availability of ground. Properly engineered, given that the plug is not polarized, there must be sensors within the brick itself to determine which is which. I have several antique radios from pre-WW2 that don't have that circuitry and which, if you insert the plug reversed, the chassis will have voltage on it. For safety, I've changed the plugs to be polarized so that the chassis never has voltage on it.

In the Apple bricks, the mains current is isolated from the Mac side through opto-isolators and other components. So while the article has a good speculation on what Apple did, the actual design within the brick is such that no voltage should ever be available to the case of any Mac that is using Apple chargers. Now, third party power supplies are a totally different situation because they may or may not have the same opto-isolation, which makes them riskier to use. (I have read somewhere a comparison of Apple and non-Apple charging bricks and none of the non-Apple bricks had the safety features of the Apple products. I just can't find those links at the moment, or I'd include them.)

Frankly, all of the hacks on that site just look hugely risky and impractical. The thin wires used for ground can't carry much current in the event of a short, so they are going to burn out pretty quickly if needed. Combine that with a third-party charger with poor safety engineered in and you have a recipe for a disaster.

In any event, if the ground circuitry is that critical to the system, or safety, Apple would not have a two-prong duck head connector. And if two prongs is ok for duckhead, why not have a two prong extension cable? It still makes no sense at all.

 

[Lifeisabeach]

In any event, if the ground circuitry is that critical to the system, or safety, Apple would not have a two-prong duck head connector. And if two prongs is ok for duckhead, why not have a two prong extension cable? It still makes no sense at all.

Maybe they don’t make a two-prong extension cable because “any” figure 8 one will do? Ok, I’m stretching on that since it’s not something they even make people aware of. I don’t have a good answer, but given the observation made in one of those articles about feeling current leakage when not using a ground, methinks that using a two-prong, including the duck head, should be avoided when feasible. It obviously is “safe enough” to use the duck head with two prongs, or Apple would have been sued into oblivion long by now. Maybe their thinking is that extending the length of the line via that cord vs the duck head warrants the extra precaution?

 

[MacInWin]

Maybe their thinking is that extending the length of the line via that cord vs the duck head warrants the extra precaution?

Maybe, but the logic for that is really thin. As for the safety of the system with or without that grounding, the UL process is supposed to check for that, plus failure modes of the internals. As I said, Apple's design uses opto-isolators which means that no electrons entering through the mains wire reach the laptop. (If you don't know what opto-isolators do, here is the wikipedia article on them. https://en.wikipedia.org/wiki/Opto-isolator ) They get converted through the various transformers and finally the opto-isolators use photons to move the power from the mains side to the output side. And that is why third party power bricks that take the cheaper way of not using opto-isolators are risky, because if they fail, direct mains power CAN get through to the Mac. Also technically, the absence or presence of the ground doesn't impact the safety of the unit either, because it's all encased in the insulating case and the output power is all coming through the isolators. So no mains electrons get to the Mac, as I said. Given that isolation, you don't need ground for safety or circuit completion. Just hot and neutral.

 

[Lifeisabeach]

Maybe, but the logic for that is really thin. As for the safety of the system with or without that grounding, the UL process is supposed to check for that, plus failure modes of the internals. As I said, Apple's design uses opto-isolators which means that no electrons entering through the mains wire reach the laptop. (If you don't know what opto-isolators do, here is the wikipedia article on them. https://en.wikipedia.org/wiki/Opto-isolator ) They get converted through the various transformers and finally the opto-isolators use photons to move the power from the mains side to the output side. And that is why third party power bricks that take the cheaper way of not using opto-isolators are risky, because if they fail, direct mains power CAN get through to the Mac. Also technically, the absence or presence of the ground doesn't impact the safety of the unit either, because it's all encased in the insulating case and the output power is all coming through the isolators. So no mains electrons get to the Mac, as I said. Given that isolation, you don't need ground for safety or circuit completion. Just hot and neutral.

Nope, not a clue as to what they are, but I’ll defer to your assessment since this seems to be up your alley. ?