Cheap USB phone chargers are potentially dangerous

[Ben321]

There's a lot of phone chargers out there that don't ship with the phones they were meant to charge (and aren't even made by the companies of the phones they are designed to charge), and aren't even made by major electronics manufactures (such as Intel, GE, Sony, or other companies you would tend to trust with making electronics). These chargers often have no logo on them at all, or have some logo you don't recognize, because they come from some company that most Americans never would have heard of. These chargers tend to be made by small Chinese companies. And from my understanding they tend to be defective too, especially in the category of electrical safety. They tend to be very cheap, like in the $1 to $5 price range, and can be found at many stores that aren't even electronics stores. You know how a lot of stores have a rack of cheap items (usually things like candy bars) they hope you will buy on your way out, right near the checkstand? Some stores have other super-cheap Chinese junk electronics in these same areas, and I've even seen some of these cheap Chinese phone chargers (as well as similarly cheap LED flashlights, etc).

I've actually heard quite a few bad things about these cheap chargers. I've literally heard about people electrocuted by them. Well, at least I THINK it's these cheap junk chargers (and not legit ones made by Samsung, Apple, etc) that caused the electrocution. Unfortunately I can't verify this, as when I have read stories about this, they usually simply mention that somebody got electrocuted by using their phone as it was charging, making absolutely ZERO MENTION as to whether the charger was an original charger that came with the phone, another charger from the same company that made the phone, some charger from another trusted company, or a cheap junk "dollar store" type charger that was made by some no-name company.

Does anybody here have more info on some of these incidents, info that maybe wasn't mentioned in the news stories put out by major news companies?

[tunk]

Diodegonewild has a handful of youtube videos about cheap chargers (including full teardowns).
There's also quite a few tests here: https://lygte-info.dk/info/indexUSB%20UK.html

[ataradov]

The issue here is that most of the reviews are highly hypothetical. It is hip to discuss creepage distance, makes you sound cool and smart. Most of the time even the worst looking changer are perfectly fine.

In many of those stories people are using phones while taking a bath and charging. Or another common thing is to use broken cables, since Apple cables are so expensive. I see people do that all the time, unfortunately.

I too would like to see a legitimately bad design that actually traceably lead to a death or other serios damage.

[Ben321]

The issue here is that most of the reviews are highly hypothetical. It is hip to discuss creepage distance, makes you sound cool and smart. Most of the time even the worst looking changer are perfectly fine.

In many of those stories people are using phones while taking a bath and charging. Or another common thing is to use broken cables, since Apple cables are so expensive. I see people do that all the time, unfortunately.

I too would like to see a legitimately bad design that actually traceably lead to a death or other serios damage.

How would a broken cable shock you? 5 volts isn't the cause of the electrocution, no matter how broken the cable is, or if you were charging in a bath. The problem is that the mains voltage is somehow getting on the output. The output of a low voltage power supply should NEVER be electrically coupled to the input, only magnetically coupled via the step-down transformer (which is also the switching transformer if you are talking about a switching supply, not just a simple linear supply). The problem with electrocution from the low voltage output power supply is the result of one of two things. Some piece of metal at the factory somehow got inside the power supply's case before it was closed, and electrically connected the primary to the secondary, or alternatively a failure in the transformer (likely too heavy a load was attached to the output so overheating of the transformer to the point that the enamel insulation around the wire burned off and also melted off the tape insulation between the primary and secondary winding layers), and allowed the primary winding metal to touch the secondary winding metal). So whether it was a piece of metal getting in it, or whether the transformer was designed below spec so it overheated even when operating the intended load, it still is the result of a factory error, which mostly happens in poorly run factories trying to make things cheaply so as to make a product they can sell cheaply.

[ataradov]

How would a broken cable shock you? 5 volts isn't the cause of the electrocution, no matter how broken the cable is, or if you were charging in a bath.

Broken cables are mostly the reason for fires. Sooner or later 5v line shorts out.

[Ben321]

How would a broken cable shock you? 5 volts isn't the cause of the electrocution, no matter how broken the cable is, or if you were charging in a bath.

Broken cables are mostly the reason for fires. Sooner or later 5v line shorts out.

I was thinking about the electrocution issue. So if it shorts out then it will overheat right? Or is there some fuse in it, or other short-circuit protection circuit of some kind?

[ataradov]

So if it shorts out then it will overheat right? Or is there some fuse in it, or other short-circuit protection circuit of some kind?

It may cause overheating, or straight up sparks. Even if there is some protection circuit, it would be set above 0.5 A or 2.5 A, depending on the charging standard, and that's plenty to cause a fire. It does not need to be a full short.

This is not specific to cheap chargers, it happens with real ones too. It is more of a cable issue. There are a lot of pictures of that happening in google. In a lot of them you can see that the source of the heat is somewhere close to the phone part of the cable, but no the socket itself.

[Raj]

Never trust Chinese SMPS (same tech as most chargers)...I bought an atx power supply, didn't check it's output and it burnt everything but itself in my PC. 
It was outputting 15v on 12 v line. 

[Raj]

True...Though I thought that It was made in India...Until it burnt my system and I tore it down to find PCB marked "made in China". Intex, though is very popular in India, it pretends to be Indian, when it's not.

[Gyro]

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.

[Ed.Kloonk]

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

"Bloody Hell!"

[Gyro]

...but he says it in such a nice accent! 

[tunk]

There's also this page which does teardowns. No reviews as such and no
teardown of transformers, but it does give an indication of (build) quality:
https://translate.google.com/translate?sl=zh-CN&tl=en&u=https://www.chongdiantou.com

[Ed.Kloonk]

...but he says it in such a nice accent! 

And he talks about his cat more than Mrs. Slocombe.

[BrokenYugo]

Given Diode's love for HV I'm surprised he hasn't cooked up some sketchy hipot tester (NST and a variac?) to push these sketchy transformers to breakdown and see if they arc over where he suspects.

Could be an interesting test for somebody with some sort of mains transient generator too. How much of a pulse will the insulation on cheap enamel wire take?

[Gyro]

The search for a safely wound transformer (or even Y rated cap) continues... 

[amyk]

In many of those stories people are using phones while taking a bath and charging.

In other words, Darwin Award candidates... if I'm in the bath I'm almost certainly going to be there because I'm cleaning myself, and have better things to focus on than playing around with an electronic device. I recall a story about someone who used several extension cords so she could take her phone in there.

There must be a reason some regulations don't allow mains outlets in bathrooms at all, and some allow only with isolation transformer/GFCI.

[Ed.Kloonk]

The search for a safely wound transformer (or even Y rated cap) continues... 

Bloody Hell!
 

[Haenk]

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).

[Raj]

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.

[srb1954]

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.

[Gyro]

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.

The "grounded metal chassis" doesn't help you either (quite the reverse) when the USB supply that it is connected to becomes live.

Edit: Especially when dropped into a bath.

[james_s]

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

I'm not going to test the theory, but I suspect that dropping it into the bath is a lot less likely to result in harm than holding onto it while sitting in the bath. If you drop it then the shortest path to ground is likely going to be through the water (with salts from your body dissolved) to the drain fitting rather than through your body. If you're holding it in your hand then any leakage is going to go through your arm and into your chest. Either way I would never hold onto something plugged into the wall while I was in the bath or shower.

[Ed.Kloonk]

Either way I would never hold onto something plugged into the wall while I was in the bath or shower.

Hot water tank?

How many of us bathe or shower everyday (British people not withstanding) hoping the insulation around the heating element is as good as the tank's connection to Earth?

 

[james_s]

Either way I would never hold onto something plugged into the wall while I was in the bath or shower.

Hot water tank?

How many of us bathe or shower everyday (British people not withstanding) hoping the insulation around the heating element is as good as the tank's connection to Earth?

 

Well in most older homes at least the pipes are metal and have to be bonded to ground, and the clean fresh water flowing through the water tank is typically a pretty good insulator so I think getting a shock through the water is unlikely even if the tank were not grounded. We don't have those electric showers that heat the water right near the shower or even right in the head though.