Cheap USB phone chargers are potentially dangerous - Page 1
Forum section: electronics / general

author: Ben321
author_rank: Frequent Contributor
timestamp: April 24, 2021, 10:50:39 pm
content: 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?

author: tunk
author_rank: Super Contributor
timestamp: April 24, 2021, 10:56:50 pm
content: 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

author: ataradov
author_rank: Super Contributor
timestamp: April 24, 2021, 11:09:03 pm
content: 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.

author: Ben321
author_rank: Frequent Contributor
timestamp: April 24, 2021, 11:53:31 pm
content: Quote from: ataradov on April 24, 2021, 11:09:03 pmHow 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.

author: ataradov
author_rank: Super Contributor
timestamp: April 25, 2021, 12:23:11 am
content: Quote from: Ben321 on April 24, 2021, 11:53:31 pmBroken cables are mostly the reason for fires. Sooner or later 5v line shorts out.

author: Ben321
author_rank: Frequent Contributor
timestamp: April 25, 2021, 12:42:32 am
content: Quote from: ataradov on April 25, 2021, 12:23:11 amI 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?

author: ataradov
author_rank: Super Contributor
timestamp: April 25, 2021, 01:05:32 am
content: Quote from: Ben321 on April 25, 2021, 12:42:32 amIt 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.

author: Raj
author_rank: Frequent Contributor
timestamp: April 25, 2021, 03:49:34 am
content: 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.

author: Raj
author_rank: Frequent Contributor
timestamp: April 25, 2021, 08:32:29 am
content: 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.

author: Gyro
author_rank: Super Contributor
timestamp: April 25, 2021, 09:18:46 am
content: 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.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: April 25, 2021, 09:24:47 am
content: Quote from: Gyro on April 25, 2021, 09:18:46 am"Bloody Hell!"

author: Gyro
author_rank: Super Contributor
timestamp: April 25, 2021, 10:24:35 am
content: ...but he says it in such a nice accent!

author: tunk
author_rank: Super Contributor
timestamp: April 25, 2021, 03:15:27 pm
content: There's also this page which does teardowns. No reviews as such and noteardown 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

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: April 25, 2021, 10:12:32 pm
content: Quote from: Gyro on April 25, 2021, 10:24:35 amAnd he talks about his cat more than Mrs. Slocombe.

author: BrokenYugo
author_rank: Super Contributor
timestamp: April 26, 2021, 03:13:41 am
content: 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?

author: Gyro
author_rank: Super Contributor
timestamp: April 27, 2021, 09:29:15 pm
content: The search for a safely wound transformer (or even Y rated cap) continues...

author: amyk
author_rank: Super Contributor
timestamp: April 28, 2021, 12:10:35 am
content: Quote from: ataradov on April 24, 2021, 11:09:03 pmIn 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 usedseveral extension cordsso 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.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: April 28, 2021, 01:37:09 am
content: Quote from: Gyro on April 27, 2021, 09:29:15 pmBloody Hell!

author: Haenk
author_rank: Super Contributor
timestamp: May 02, 2021, 06:40:10 pm
content: In the news:https://www.spiegel.de/panorama/schweiz-frau-stirbt-nachdem-ihr-das-handy-in-die-badewanne-faellt-a-8f18cf10-bb6c-49db-9d32-01cca5a2437cIn short: Smartphone drops into bathtube while being charged. Dead (woman and smartphone).

author: Raj
author_rank: Frequent Contributor
timestamp: May 04, 2021, 04:05:32 pm
content: Quote from: Haenk on May 02, 2021, 06:40:10 pmHard 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.

author: srb1954
author_rank: Super Contributor
timestamp: May 04, 2021, 08:47:48 pm
content: Quote from: Raj on May 04, 2021, 04:05:32 pmThis 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.

author: Gyro
author_rank: Super Contributor
timestamp: May 04, 2021, 08:54:01 pm
content: Quote from: Raj on May 04, 2021, 04:05:32 pmThe "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.

author: james_s
author_rank: Super Contributor
timestamp: May 04, 2021, 09:24:07 pm
content: Quote from: Haenk on May 02, 2021, 06:40:10 pmI'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.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: May 04, 2021, 10:48:59 pm
content: Quote from: james_s on May 04, 2021, 09:24:07 pmHot 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?

author: james_s
author_rank: Super Contributor
timestamp: May 05, 2021, 01:05:00 am
content: Quote from: Ed.Kloonk on May 04, 2021, 10:48:59 pmWell 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.

author: BrokenYugo
author_rank: Super Contributor
timestamp: May 05, 2021, 05:33:06 am
content: Even with those "suicide showers" it's shockingly (no pun intended) hard to get dangerous current out of one.https://youtu.be/jiErqUkw690

author: Haenk
author_rank: Super Contributor
timestamp: May 06, 2021, 02:28:28 pm
content: Quote from: srb1954 on May 04, 2021, 08:47:48 pmI 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...)

author: Ben321
author_rank: Frequent Contributor
timestamp: May 07, 2021, 07:59:11 pm
content: Quote from: Raj on May 04, 2021, 04:05:32 pmNot 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.

author: TimNJ
author_rank: Super Contributor
timestamp: May 08, 2021, 03:04:28 am
content: Quote from: Gyro on April 25, 2021, 09:18:46 amA proper "micro" SMPS tranformer is wound with triple insulated wire (TIW, for short) for the primaryorthe 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

author: Raj
author_rank: Frequent Contributor
timestamp: May 08, 2021, 05:12:49 pm
content: Quote from: Ben321 on May 07, 2021, 07:59:11 pmYou'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)Quote from: srb1954 on May 04, 2021, 08:47:48 pmDepends 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)

author: Haenk
author_rank: Super Contributor
timestamp: May 09, 2021, 04:53:25 pm
content: Quote from: Raj on May 08, 2021, 05:12:49 pmI 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.

author: AndyFl
author_rank: Newbie
timestamp: May 11, 2021, 01:09:07 pm
content: The BigClive "The cheap shitty pink USB charger from China song", only 80 seconds long.(someone had to post it)

author: Alti
author_rank: Frequent Contributor
timestamp: May 11, 2021, 02:42:26 pm
content: For those who underestimate the scale of the problem,link to Rapex post.

author: Distinctly Average
author_rank: Contributor
timestamp: May 15, 2021, 06:42:42 pm
content: 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.

author: Raj
author_rank: Frequent Contributor
timestamp: May 20, 2021, 03:50:33 am
content: F it... this one went bad in storage, somehowDiscovered a charger in my inventory that gives shocks...40v potential to electrical ground

author: G7PSK
author_rank: Super Contributor
timestamp: May 23, 2021, 03:35:15 pm
content: 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.

author: mikerj
author_rank: Super Contributor
timestamp: May 23, 2021, 07:52:24 pm
content: Quote from: Raj on May 20, 2021, 03:50:33 amMany/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.

author: Raj
author_rank: Frequent Contributor
timestamp: May 24, 2021, 03:43:06 am
content: Quote from: mikerj on May 23, 2021, 07:52:24 pmTrue...usually a ground pin, resistor solves it...but no charger has it. Also, it shouldn't be painful to touch.this one is

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 28, 2021, 11:02:36 pm
content: Quote from: BrokenYugo on May 05, 2021, 05:33:06 amYeah. I wouldn't like to play too much with them myself.Electroboom made a video on those:

author: james_s
author_rank: Super Contributor
timestamp: May 30, 2021, 05:56:31 pm
content: Quote from: G7PSK on May 23, 2021, 03:35:15 pmI 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.

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 31, 2021, 03:17:08 pm
content: 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.

author: AVGresponding
author_rank: Super Contributor
timestamp: June 01, 2021, 05:10:39 pm
content: Or just use old-style transformer based plugtop PSUs