Cheap USB phone chargers are potentially dangerous

[BrokenYugo]

Even with those "suicide showers" it's shockingly (no pun intended) hard to get dangerous current out of one.

https://youtu.be/jiErqUkw690

[Haenk]

This is incorrect. The general consensus is that if you are gripping something in your hand an electric shock will cause muscles to contract and cause your grip to tighten.

I can confirm this. Your muscles contract and you feel like being hit with a very large hammer.
(2 of 7 lives spent on electricity, one in hospital, so that's still a good 4 lives left...)
(sidenote: that was only from touching, not holding, luckily...)

[Ben321]

Hard to do these days, considering all phones have a grounded metal chassis. You won't even be able to hold it without reflexes making you throw it away.

Not all phones do. iPhones maybe, but none of the Dndroid phones I've had are anything other than a plastic chassis. There may be a metal foil RF shielding layer INSIDE the plastic, but the outer material of the case is certainly plastic. I've had both a Motorola Droid MAXX and a Motorola Moto g6. Both have a plastic chassis, plus I always use a fully plastic phone-case (both front and back of the case are plastic) on my phone. The ONLY electrical connection that can occur would be water seeping between a button and the edge of the hole in the chassis cut for that button (this gap is about a half mm, possibly less). Theoretically if you were in a bath tub, with wet very hands, water could slowly seep into the phone through that route, and eventually make contact with a solder point inside the phone. If the USB charger had failed in a way that put the output side of the power supply at 120VAC, and your body was grounded due to being in bath water, then you could easily get electrocuted. And it wouldn't matter if the phone continued to work. The phone could continue to work, because the relative voltages between the pins on all the components in the phone would be correct. It's just that the entire circuit would now be floating at a 120VAC offset relative to ground.

[TimNJ]

Looking at DiodeGonWild's most recent USB charger teardown video (and the earlier ones), I'm seriously beginning to doubt whether it's even possible to achieve proper creepage and clearances in those tiny transformers!

He goes to the extent of completely unwinding the transformers and some of the clearances he finds are apalling. Given the manual labour intensive nature of these parts, it's hard to see how there can be decent consistency. Even if they pass a Hipot test when new (assuming they ever get one), it's a bit of a stretch to assume that they wouldn't break down after a period of use. Just because the PCB clearances look fine, doesn't mean that the transformer is anywhere near fine.

Given the small dimensions of the cores in these things and the wire thickness of the secondaries, maintaining proper edge margins leaves very little width for the actual windings. The bend radius and proximity of the wires crossing the margins to connect to the pins is another issue.

I'd love to see teardowns of a mainstream manufacturers' tiny chargers, to see how much better their transformers are, and what techniques they employ to get around the issues in a repeatable fashion. Maybe they use triple insulated wire, but there's precious little space.



(He's beginning to give Big Clive some decent competition.

A proper "micro" SMPS tranformer is wound with triple insulated wire (TIW, for short) for the primary or the secondary. Does not need to be both. Where insulation needs to be stripped back/burnt off for pin terminations, common practice is to slip a piece of Teflon tubing back over the wire near the solder termination.

https://www.furukawa.co.jp/tex-e/en/product/texe_series.html

[Raj]

Hard to do these days, considering all phones have a grounded metal chassis. You won't even be able to hold it without reflexes making you throw it away.

Not all phones do. iPhones maybe, but none of the Dndroid phones I've had are anything other than a plastic chassis. There may be a metal foil RF shielding layer INSIDE the plastic, but the outer material of the case is certainly plastic. I've had both a Motorola Droid MAXX and a Motorola Moto g6.

You've managed to keep them alive for so long? Good.
I mean all the phones with glued in screens and screw-less-ness have atleast a metallic grounded border. (BTW they all copy iphone 6) (eg my moto 8.1) and speaking from experience, my pal's charger had faulty Y rated cap, and yeah, it threw my hand away when I touched my phone, that was connected to it. (never again, that I used that charger)

In the news:

https://www.spiegel.de/panorama/schweiz-frau-stirbt-nachdem-ihr-das-handy-in-die-badewanne-faellt-a-8f18cf10-bb6c-49db-9d32-01cca5a2437c

In short: Smartphone drops into bathtube while being charged. Dead (woman and smartphone).

Hard to do these days, considering all phones have a grounded metal chassis. You won't even be able to hold it without reflexes making you throw it away.

This is incorrect. The general consensus is that if you are gripping something in your hand an electric shock will cause muscles to contract and cause your grip to tighten.

Depends on the order of operation. Like if you connect charger then turning the switch on after placing the phone somewhere, the next time you touch it, phone throws your hand away. (man, why do westerners not use switches? makes stuff a lot safer, like imagine, connecting something and it blows up in your hand, with a switch, hand is away from object)

[Haenk]

Depends on the order of operation. Like if you connect charger then turning the switch on after placing the phone somewhere, the next time you touch it, phone throws your hand away. (man, why do westerners not use switches? makes stuff a lot safer, like imagine, connecting something and it blows up in your hand, with a switch, hand is away from object)

I doubt this is a westener problem - I'd like to have switch in many of my electronic items. After all "no switch" probably became standard with the introduction of remote controls, so a hot standby was always required anyway and many modern electronics really need to boot up, which takes a while.
Still no reason not to implement a switch on your chargers.

[AndyFl]

The BigClive "The cheap shitty pink USB charger from China song", only 80 seconds long.

(someone had to post it)

[Alti]

For those who underestimate the scale of the problem, link to Rapex post.

[Distinctly Average]

A few years back I was involved in doing some testing of camera batteries and their chargers. OEM batteries will often only charge on OEM chargers in the camera world. Third party batteries will often not charge on OEM chargers, so are sometimes sold with the third parties own charger.

So after a lot of testing we found some batteries and chargers were pretty good. Lasting almost as long as the OEM batteries with all the expected safety features.

However, there was some real dross. One battery, rated at a supposed 2480mah barely made 400. When we dismantled it we found a couple of cheap recycles lion cells inside with no protection whatsoever. The charger supplied with it was nothing more than a capacitive dropper. The terminals of the charger would give more than a bit of a tingle. These chargers and batteries were sold through Amazon at the time, fortunately they have gone now. They are still available on the bay of fleas.

That was a few years ago and I have spoken about it a few times online, sometimes with a bit of derision from people who want to justify their own choices. At the back end of last year I bumped into a photographer friend who I had not seen for a bit. He was on crutches and when I asked what had happened apparently a third party camera battery had exploded in his pocket. It took three surgeries to get him back on track from the resulting damage. He is getting better slowly and hopes to be walking unaided soon. Quite scary really but on the plus side it was only his leg and his love spuds escaped the burns.

[Raj]

F it... this one went bad in storage, somehow
Discovered a charger in my inventory that gives shocks...40v potential to electrical ground

[G7PSK]

The story I read about some one getting electrocuted while using her phone  on charge in the bath did so because she used an extension cable to get the charger close enough to the bath and balanced the end of the mains extension on the side of the bath, not the fault of the charger at all but the idiot who decided to put an extension lead onto the side of the bath, further more a lead with frayed wiring. This took place somewhere in the far east, Vietnam or somewhere in that area as I recall.

[mikerj]

F it... this one went bad in storage, somehow
Discovered a charger in my inventory that gives shocks...40v potential to electrical ground

Many/most of these chargers have a small amount of leakage due to the EMI suppression cap that connects the primary to secondary, and this includes the OE chargers from Apple etc.  The impedance should be very high though, you'll only get some microamps of current.

[Raj]

F it... this one went bad in storage, somehow
Discovered a charger in my inventory that gives shocks...40v potential to electrical ground

Many/most of these chargers have a small amount of leakage due to the EMI suppression cap that connects the primary to secondary, and this includes the OE chargers from Apple etc.  The impedance should be very high though, you'll only get some microamps of current.

True...usually a ground pin, resistor solves it...but no charger has it. Also, it shouldn't be painful to touch.
this one is

[SiliconWizard]

Even with those "suicide showers" it's shockingly (no pun intended) hard to get dangerous current out of one.

https://youtu.be/jiErqUkw690

Yeah. I wouldn't like to play too much with them myself.
Electroboom made a video on those:

[james_s]

The story I read about some one getting electrocuted while using her phone  on charge in the bath did so because she used an extension cable to get the charger close enough to the bath and balanced the end of the mains extension on the side of the bath, not the fault of the charger at all but the idiot who decided to put an extension lead onto the side of the bath, further more a lead with frayed wiring. This took place somewhere in the far east, Vietnam or somewhere in that area as I recall.

I know there was at least one case I read about where the shock came via the body of the phone, not from the mains lead itself. Receptacles in the bathroom are a standard thing in North America and probably some other parts of the world. Not isolated shaver sockets but ordinary 120V 15A receptacles, it's totally conceivable that someone could sit in the bath with their phone plugged into the wall using a not so unusual 6' charging cable. Houses built in the last 40 years or so will have GFCI protection on the bathroom receptacle but there are still older houses around that do not.

[SiliconWizard]

Yep... to be fully safe in this kind of use case, the chargers should be isolated - such as typical "medical" power supplies. That's not cheap.

[AVGresponding]

Or just use old-style transformer based plugtop PSUs