Laptop giving me shocks when plugged in abroad
June 8, 2017 10:38 PM   Subscribe

My laptop's plug is not grounded. In the US that was not an issue, but for whatever reason, in Australia that means the laptop case is giving me mild shocks while it's plugged in. What can I do to ground it? Do I need to buy an aftermarket power cable?

Laptop is a Lenovo Ideapad:
posted by LSK to Computers & Internet (15 answers total) 1 user marked this as a favorite
I'd have thought you absolutely need something other than the stock cable/power supply. Australian walls put out 240v as opposed to the 120(?) volts in the US. Do you have any sort of step-down transformer between the wall and the power supply?
posted by quinndexter at 12:29 AM on June 9, 2017

> I'd have thought you absolutely need something other than the stock cable/power supply. Australian walls put out 240v as opposed to the 120(?) volts in the US.

(This is no longer true, for things like laptop and phone chargers. Most recent chargers will be a "switching power supply" that will accept 100-240 V AC input and produce constant DC output. Check the label on the power supply. Older electrical items which are not "smart" like a kettle or perhaps a washing machine will need a transformer if you take them from the US to Australia. This doesn't answer the main question, sorry!)
posted by richb at 2:12 AM on June 9, 2017 [1 favorite]

Response by poster: Confirming richb's statement - my laptop's charger accepts 100-240v input
posted by LSK at 3:48 AM on June 9, 2017

You should just be able to get an Australian laptop power cord and plug it into the power supply brick without trouble, this will have an earth pin and may fix things.


Electrically, running your laptop in Australia is no different to running it in the US, what has probably changed will be something to do with your carpet, your clothing, your furniture or something of that nature that is causing static electricity to cause you problems, it probably won't be the power supply or your laptop.
posted by deadwax at 4:19 AM on June 9, 2017 [1 favorite]

Is it giving you sharp shocks or just an unpleasant tingle? Lots of laptops have a power supply design that allows a tiny amount of current to leak when you are grounded and the laptop is not grounded. It can be slightly unpleasant to feel but it's not dangerous. This HP article explains more.

Using a grounded mains cable may stop it, but doesn't work for every laptop.
posted by samj at 6:26 AM on June 9, 2017

what has probably changed will be something to do with your carpet, your clothing, your furniture or something of that nature that is causing static electricity to cause you problems

Also humidity in the air - are you in a climate drier than what you are used to?
posted by Dr Dracator at 7:33 AM on June 9, 2017

If the outlet isn't grounded, then using a grounded cable on the laptop will not do anything to stop the shocks (here's how I know that).
posted by fuzz at 7:52 AM on June 9, 2017

By that I mean that the outlet doesn't just have to have an extra pin for the ground, but also that the pin has to actually be connected to ground behind the scenes.
posted by fuzz at 8:12 AM on June 9, 2017

In Australia the outlet will be grounded, barring very serious (and extremely uncommon) wiring non-conformance.
posted by deadwax at 2:36 PM on June 9, 2017

Fixing this issue costs about $2.50.
posted by flabdablet at 10:42 AM on June 10, 2017

The cause, by the way, is that the switched-mode power supply in your laptop's power brick has a Y capacitor fitted between supply main earth and the hot side of the power supply, and an X capacitor between mains earth and one side of the DC power to the laptop.

Those capacitors are there to prevent the cables attached to the power supply from radiating its internal high-frequency switching noise as electromagnetic interference. They're quite a low capacitance with a high voltage rating and they're designed to break down safely if they break down at all, so they don't pose a safety hazard even if the power supply doesn't end up actually grounded. If it isn't, though, they have the unfortunate side effect of coupling a tiny trickle of 50-60Hz mains AC to the chassis of your laptop, which you will perceive as a tingle if conditions are right.

If you're getting tingles in Australia that you don't get in the US, that will be because Australian mains voltage is twice as high to begin with, meaning that the tiny trickle making its way through the Y and X capacitors ends up somewhat less tiny when finally delivered to you.

It's not a health risk but it is kind of irritating, and using a properly earthed Australian supply cord instead of your US cord with a travel adaptor will certainly get rid of it.
posted by flabdablet at 11:08 AM on June 10, 2017 [2 favorites]

The leakage current from mains hot to mains earth that those EMI reduction capacitors cause by design can also be enough to cause regular nuisance trips on any GFCI breaker protecting a circuit supplying a few tens of computer power supplies. At the school I used to be ICT technician for, two of the buildings would regularly go dark about twice a week just because there was a GFCI breaker on a circuit that had to supply about 30 desktop computers and a few digital projectors and classroom TVs, all of which have switching power supplies.

No fault was ever found with the GFCI, which was repeatedly tested and shown to be working exactly to spec. It's just that a GFCI can't see any difference between the earth leakage currents from 50 devices that each leak a couple of hundred microamps to earth by design vs. a careless human sticking a knife in the toaster.
posted by flabdablet at 11:27 AM on June 10, 2017 [1 favorite]

Yup, unless you're running a hair dryer or something most modern electronics with an actual power brick will just need the adapter for the "Y" configured Australian plugs (just got back from OZ, phone and laptop charger worked fine).

That three-prong cord flabdablet posted won't actually fit in the power brick if the brick is anything like the replacement part that comes up for me, which doesn't provide a third space for the ground wire. I see some cords like this one, but that presumably won't help with the grounding/capacitance issue.

Maybe try something like this? The shape is a little annoying with some Australian outlets because they often have their own built-in breaker switch conveniently placed around where the housing of this thing wants to be, but I used this all over Oz with no issues.
posted by aspersioncast at 11:36 AM on June 12, 2017

Yeah, that's the 45 watt wall wart version. The 65 watt brick has a standard cloverleaf mains entry socket that accepts grounded cables.
posted by flabdablet at 8:03 AM on June 13, 2017

And no, that grounded travel adaptor won't change anything. The adaptor itself has a ground pin, but unless the laptop's power supply is actually connected to it (which it won't be, if it's the US wall wart type you linked to or a 65 watt brick with a 2-pin US cord attached) then the leakage current through the Y and X capacitors inside the supply will still end up available at the laptop chassis for your tingling excitement instead of dissipating to earth.
posted by flabdablet at 8:07 AM on June 13, 2017

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