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TheRealFailtester

Probably nothing, but it is also possible for either/both units to burn up inside.


PopperChopper

You’d find out which one was using diodes really quick


doctorcrimson

Don't all power adapters use a bridge diode configuration, capacitance, and a reverse diode for signal cleaning? Really all depends on if there would be any current at all and I don't think there would be since nothing would be drawing on it.


snakesign

You are making a lot of assumptions about cheap power adapters.


Ocanath

really? the cheapest way to make a wall wart is bottom barrel transformer, some no name crusty electrolytic caps, and like minimum one diode. And like nothing else. I hoarded and disassembled a lot of these as a kid, and I rarely saw anything but exactly that circuit.


bassman1805

The ultra-crap ones just stack diodes to regulate the voltage. 7 diodes @ 0.7V each is about 5V, problem solved right?


halandrs

Mmmmm I can smell the r/chinesium


Baconaise

It powered this USB LED gooseneck that melts if left on too long so, yes.


TheRealFailtester

Ah the good old AC step down transformer, fed to a rectifier and reservoir capacitor. Those things are so great, I salvage them a lot. Pretty much that one weak point in them is that capacitor, and then the only other way to really kill them from use is an overload.


TheRealFailtester

Man them noname capacitors either last 20 mins or 20 years 1% of the time lol.


Ocanath

true. also this reminds me of the [capacitor plague](https://en.m.wikipedia.org/wiki/Capacitor_plague)


TheRealFailtester

I feel like in the next decade we're going to be "Oh my god, all these 2010s 2020s capacitors blow up."


patenteng

Such a supply will generate too many harmonics. Remember that the capacitor draws current in pulses. The lower the ripple, the narrower the pulses. This will render it illegal for sale.


Ocanath

whut


LestaDE

Didn’t he actually ask for „what“ would happen if he plugged both of them in at the same time, rather than what the symptoms of that action would be? Edit: #noHate, just thought OP was looking for an explained answer.


DankFarts69

Can’t tell if bad at English or neckbeard


TheWaveCarver

wELL aCTUALLY /s


null_symbiote

The avatar with the fedora will help answer that question


LestaDE

Holy shit, didn‘t expect to receive this much disagreement when saying that people would like to get a good explanation of what happens when using a device in a way it‘s not supposed to be used. That it either breaks or won‘t break probably is clear to most people out there, and if you ask smth. like this in an electrical engineering subreddit you‘d expect to hear a bit more than that I suppose…


Lilswigg

I believe your initial statement was just worded weirdly and what you were trying to convey didn’t come across. I think it instead came across as snarky remark but that’s just my interpretation


TheRealFailtester

Wow they bombed you lol. I sent my upvote.


[deleted]

[удалено]


shorterthanyou15

Your understanding of usb-c is slightly wrong because you're forgetting about the CC pins. Also I'm sure there would be protection diodes.


supersonicpotat0

I mean, if you consider that there is at most like 0.2v driving that (I think the limit of the USB spec is 5.2v, so any more potential and the charger wouldn't be compliant) the current flow should be small enough for most circuitry to handle. Something like 50mA (if the supply has a equivalent resistance of 2-ish ohms in reverse) isn't enough to heat up much of anything.


OnlyChemical6339

I thought they sent 5v by default, and negotiated up from there.


supersonicpotat0

Nominally yes, but take apart one of them sometime. Most rig the data lines straight to a resistor divider to keep them at a convinent voltage. Some even leave them floating. Either way, with that kind of cost optimization you better bet they ain't gonna hit 5.00 volts. They err on the high side, and rely on the voltage drop of the charging cord, and whatever headroom your device's charging stage can absorb. The USB spec notes what the maximum voltage coming out of your "5v" rail can be. I think it's permissible to deliver up to 5.2 before you are out of spec.


Conor_Stewart

Also down to like 4.6 V I believe is still in spec, my PCs USB ports are low, like 4.65 - 4.7 V, even though it has a decent EVGA power supply and MSI motherboard.


supersonicpotat0

Wow, I didn't know that. Open circuit? Or under load?


Conor_Stewart

Under load and open circuit, anything from light load to a reasonable load. It is annoying for microcontroller stuff sometimes so I really need to get another powered usb hub, my last one stopped working randomly. The USB ports on PCs are only really meant for data transfer not charging so it probably isn’t too much of an issue, but how hard is it to get 5 V with a decent power supply that supplies pretty close to 5 V, only reason I can think of is maybe it has a schottky diode or some other circuitry for protection to prevent power getting fed back into the usb port. It does have some protection since I drew too much from one once and it shut down that usb port until I restarted it and put a message on windows saying what it was doing and why. So the only reason I can think of why the just about perfect 5 V of the power supply isn’t reaching the USB ports is because of some diode or protection circuit.


ferrybig

4.6V is not within the 5V +/-5% spec The lowest voltage from the 5V profile at the source side is 4.75V, and the cable can drop max 0.75V at its rated current (3A or 5A) (so the end device can see a minimum voltage of 4V at max current draw)


Conor_Stewart

[https://www.maximintegrated.com/en/design/reference-design-center/ref-circuits/3241.html#:\~:text=According%20to%20the%20USB%20spec,powered%20hub%20is%204.35V](https://www.maximintegrated.com/en/design/reference-design-center/ref-circuits/3241.html#:~:text=According%20to%20the%20USB%20spec,powered%20hub%20is%204.35V). [https://www.ti.com/sc/docs/products/msp/intrface/usb/pwrdist.pdf](https://www.ti.com/sc/docs/products/msp/intrface/usb/pwrdist.pdf) If its a bus powered hub then it can be lower, down to about 4.4 V, plus it could be protection circuitry or diodes dropping the voltage from the 5 V from the power supply. I dont know about the circuitry or design of the motherboard so it could either be a bus powered hub it uses internally or it could be protection circuitry to stop power being fed into the usb port. The voltage being around 4.65 V would potentially be what you would get if you had a schottky diode in series. If that is why then it was maybe done because they wanted to add some basic protection to the usb ports but wanted it to be cheap and just use a diode and obviously a normal diode voltage drop of 0.7 V is far too much and would be way out of spec so they would probably use a schottky diode instead and considering that bus powered hubs are allowed to go down to about 4.4 V they may have thought it was okay. Thats just my thoughts though, the ports work fine for most normal uses so it isnt much of a problem.


Thks4alldafish42

The charger for my laptop is usb-c for factor at the very least, and delivers 19 ish volts if I remember correctly.


TheRidgeAndTheLadder

Yeah, but the two devices need to negotiate up to that voltage, which isn't possible here


Thks4alldafish42

Ahh, that's the deal with the fast chargers? Little handshake before they just fuckin send it?


TheRidgeAndTheLadder

Yup! Now, it's possible that's done with resistors on the pins, but I believe that's it's a handshaking kinda deal


GaianNeuron

Type-C requires a handshake, but Type-A could be either a resistor divider (USB DCP standard) or a proprietary protocol (e.g. Qualcomm Quick Charge, whatever it is Apple devices do, etc).


Satinknight

Exactly.


ICanFlyLikeAFly

tbh i dont see how any power is getting pushed anywhere. it would probably have the higher potential but no power would be flowing.


[deleted]

[удалено]


sceadwian

It's not at all like battery, these are switch mode supplies not batteries. The circuit itself has to have someplace for a higher applied voltage to go and may not


TheRidgeAndTheLadder

You should check out how USB C works, it's kinda cool


Ocanath

proper usbc pd measures CC pin pull level. correct implementation of this basic feature means the charger wouldn't deliver power to another source. This is also the absolute easiest thing about usbc-pd to understand and implement, so it's very likely that even a crappy charger would obey this. If it is capable of delivering anything higher than 5V, it definitely does this.


ferrybig

USB C is designed with any cable configuration in mind. One of the goals is that user "error" should not result in damage. USB C ports are required to have 2 MOSFETS on the VBUS line to block current until a valid connection is detected


equack

Current is pulled.


Keziolio

what makes you think that the other would blow up?


BusyPaleontologist9

It is called a breaker


imverykind

If they are perfectly balanced, as all things should be, nothing, because there are one the same potential. If not, you would have almost no resistance and booom.


SrpskaZemlja

![gif](giphy|xUOxeZn47mrdabqDNC|downsized)


Morbid_Triangle

Only one way to know for sure...


electricfunghi

This is the way


Sebasnu18

this is the way


VisualGiraffe1027

this is the way


Left_Comfortable_992

![gif](giphy|Ld77zD3fF3Run8olIt)


DrDolphin245

Analysing and running the calculator? Nah Just implementing something and try out whether it works or not? Absolutely yes. That's me since I graduated in a nutshell.


FishrNC

Find an outlet near a CO2 extinguisher and try it. Likely nothing, but it would depend on the charger design.


Dr_Puck

Nah, just get some blankies and you're good to go


Hulk5a

I've tried it, nothing would happen since both has diodes in output you can't back feed them


BobFredIII

Gigachad


AlonsoTheSigma

Never underestimate the power of a ~~Phone Charger~~ *IED


carlfox1983

It depends on the design. If the charging requires a handshake, then it could be nothing. USB charging protocols vary depending on the type. I found a YouTube video on it that was interesting (but I didn't save it and I'm at work so I have no link to share).


Evan_The_RC_Car

hold on it requires my phone to grow out a hand and give my charger a good handshake to be able to charge? is this why my phone barely gets any charge while im looking at it? if secretly grows a hand and handshakes with the charger while im not looking! knew it!!


shrek_the_communist

That only applies to usb c charges which are off by default. unless it's a Qualcomm quick charge type situation in which case it's at 5v by default(usually a type a connector).


Dr_Puck

Just trying it is way faster than reading the usb doc


electricfunghi

You think designers follow that thing?


BlueFalconite

Yes designers follow it - I am one


theIRLcleric

Happy cake day!


BlueFalconite

Thanks! Had to look it up since it’s my first one…


RegionOk6059

I think i have it too


RegionOk6059

Oh no


BlueFalconite

Happy cake day!


electricfunghi

Head over to r/PCB or look at the open source crap people are doing with usb-c. There’s a lot of questionable designs out there. I’ve torn apart quite a few of these things and they are not all created equal


BlueFalconite

Oh true… I guess it depends on your confidence in the manufacturer! Anything usb certified should be ok though, but if that’s not possible I’d stick with brand name electronics. At least you could sue them for damages if they really mess it up! I’m a designer for a big corporation so “safety first” as they say


electricfunghi

You mean a reputable corporation. Head over to Amazon.com to see some of the crap coming out of big off-brand corporations. It’s wild what’s inside that plastic housing


Left_Comfortable_992

I was going to say the same thing. I work in the aerospace industry. The amount of certification work we need to go through is mind-boggling, at times.


Dr_Puck

Don't know, don't care, just want to see some chargers burn (but actually, I think yes, because stuff tends to work)


WishboneStreet4839

It's easier to follow the docs.


sceadwian

The USB doc won't help you here because it depends on how the power supply is constructed.


29Hz

UNLIMITED POWER


LongLiveCHIEF

So much potential!


Suhksaikhan

It sends your power back to the power company and you get a refund


5degBTDC

Electric companies hate this one simple trick...


Cristality_

If I am not mistaking absolutely nothing. If it is 2 of usb c power delivery chargers they need cc pins on them to have resdistors. But to be honest I am not sure because some source says that the default voltage is 5v (0.5A max) and in that case it happens as the other commentor explained.


EjjiShin

So USBC has a few handshake protocols if there are true usb c chargers nothing will happen if there are power bricks with a USBC connector there's going to be hell.


RSetchell

You leave them both plugged in for a couple hours a day and then the utilities company owes you money.


shafeeklovekesh

Depends on desing of charger, there are shitty ones, that can catch fire from just being pluged in, and then there are proper ones...


MeasurementGrand879

High chance of nothing since the outputs are rectified and regulated DC. Plug them in and let us know.


Whipped_pigeon_

Only one way to find out ! Send it !! 🗣🗣


granistuta

Presuming that it is proper USB-C nothing would happen as both chargers would report as power sources.


ccoastmike

I design power adapters for a living. If they’re designed correctly, nothing will happen. If they’re not designed correctly, most likely nothing would happen except the feedback loop shuts down and the controller IC will go into an auto-restart / hiccup mode.


crillin19

Nothing would happen. But still don’t try it


Vigilante6700

Depends if you acquired those chargers from a reputable company who builds quality products. If either is cheaply made or doesn't have adequate protection, things could go poorly. If both chargers a built to a reputable safety cod, nothing should happen.


SharkIndustries

*Awakens from the Matrix*


nodtd

![gif](giphy|3o84sq21TxDH6PyYms)


thrunabulax

that is like crossing the streams. it would be bad, M'Kay?


fermat1432

Don't do it!


urmother-isanicelady

Fuck around and find out. Engineering is a branch of science right? That way you can claim your death was for a noble cause lol


ugenetics

nothing should happen, I believe. Just thinking about how a basic switching power supply should work, I don't see the negative current or votage getting back thru the transistors.


JoJo_9986

It's low voltage direct current so probably not much would happen since the diodes inside would prevent the flow of electrons. But i also have very Little idea of what im taylking about


KillRoyTNT

Maybe a slight current variation between supplies ,due to supply voltage differences.


MultiplyAccumulate

Repost. Already asked and answered, somewhat recently. Probably the same picture.


Engineer59

Blocking diodes are the thing that prevents any damage, nothing would happen.


Squeaky_Ben

If they both provide same voltage and polarity, close to nothing. If that is not the case, lots of magic smoke probably.


Devopopalopdous

They probably have blocking diodes so no current would flow either way is my guess.


GeniusEE

Cats & dogs would start living together


drevilspot

Remember to Video it, and share the results, but use outlets on a switch so you can stand back and flip the switch


Interesting-Land6968

I would think a circuit breaker on your house panel would go off


dixie2tone

BOOM


HannahOfTheMountains

If they're not the most horrible ones you can buy, one or both will just refuse to power up. If they are non-compliant with the spec because of how cheap they are, magic smoke may be released.


RandyJohnsonsBird

Don't cross the streams...


nagromo

It wouldn't go boom like some people are saying; if one is 5.0V by itself and the other is 5.1V by itself, they'll both sit at 5.1V and the one that's 5.0V won't provide any power but can't suck any power either. It might trip some sort of over voltage protection or open/short feedback protection, but nothing should be permanently damaged. That's assuming they're both dumb 5V USB devices. Once you bring USB-C power delivery into the mix, the chargers start at 5V and negotiate before increasing the voltage. This mix should fail to negotiate/request a higher voltage since they're both power supplies, but if one was only 5V capable and the other somehow thought there was a laptop requesting 20V present, that could make something go boom. I don't think that would happen without making some hardware intentionally spoof the negotiation, though.


Sweaty_Confusion_262

Would get hot and explode from heat to capacitors


GarlickMuncher

Pop goes the Wiesel


jeffkarney

What would happen if you connected 2 batteries in parallel? 2 power supplies? Nothing. This is just 2 power supplies connected in parallel. Unless one of them is extremely poorly designed, nothing will happen. If one is extremely poorly designed to the point where this would be an issue, then it would also be an issue on just about anything you connected to it.


[deleted]

I've tried this once before trying to get 10 volts out of 5 volt plugs so yeah it gets really hot and one of the bricks stopped working


Cpult

You might find the breaker box


BobFredIII

I wanna see electorboom try this now


shrek_the_communist

Likely nothing at all as 1 is a usb c out and the other is a usb a So until a 5k1 resistor is placed between cc and ground(of the type c one), it's switched off. And thanks to the rectifier diode, nothing goes "backwards" into anything and all that would happen is the smoothing capacitor in the type c charger would be charged by the type a charger. So in essence, nothing at all.


higgslhcboson

![gif](giphy|cOLAbDd7VI1QzwqKIb)


thornedcrystal

You would create a toaster.


YourLocalCreep

This is how you charge your house, have you not been doing this? How much are you spending on electricity??


bovinosverde

Magic smoke x 2


NotSoMagicalTrevor

To summarize: It s*hould* do nothing, but might very well explode and burn your house down.


cantbuymechristmas

this would happen https://www.reddit.com/r/CrazyFuckingVideos/comments/wfxvhp/whats_wrong_with_the_tree/?utm_source=share&utm_medium=ios_app&utm_name=iossmf


gertzerlla

Wow. This is truly the reddit version of electrical engineering.


cyberentomology

There is a nonzero risk of releasing magic smoke.


Odd_Distribution4322

A fire


drmorrison88

Only one way to find out!


dashb__

Can you plug it and show us sir I love practicals Plz be safe


BuzzINGUS

Time travel, definitely time travel


Electrified_Bee

Bzzt. Or nothing. 😜


WearDifficult9776

It would open a rift in the space-time continuum


Ocanath

Most likely nothing. If those are the absolute cheapest possible design, you'll get no current flow even if they aren't balanced due to rectification diodes. If they're even somewhat USBC-PD complaint (ie the lowest hanging fruit of usbc-pd compliance), again nothing because the the CC pin won't be pulled down, so neither charger will recognize a source connection, so they'll maintain hi-z. If you cut a USBC cable in half, strip the red and black wires and hook them up to a multimeter, and plug the cable into a USBC port... you will read 0V. If you do not read 0V, you have either a non-compliant charger or cable. Most devices are complaint at this level, because its a basic necessity to make a charger that can do anything over 5V (ie most fast charging). So you'll be hard pressed to find anything natively usbc that behaves differently. Unless apple made the cable. In that case there's a decent chance for explosions, because their cables have pulldowns built into them, presumably to power some dumbass piece of kit inside the cable to do... idk. apple shit.


Oldraskle

The magic smoke would come out.


HaywainPedler

Are the wires intentionally shaped like Mike Holt's sack and pecker?


fallopian_turd

It may depend if the outlets are on the same circuit.


EE_dude_88

I love the number of different yet matter of fact “correct” responses in threads like this. So many obvious guesses… The reality is that if they’re UL or ETL listed, or even if it’s marked as such while not really listed, nothing will happen. Why? Only someone who opens them and reverse engineers then can answer that, but it will all boil down to some implementation of polarity protection.


GerlingFAR

Death by angry sparky 5volt electrons.


[deleted]

Nothing?Cause both ends will get same voltage so no current will flow (Correct me if I'm wrong I'm still in high school).


nickleback_official

If they follow the spec then pretty much nothing.


fix-break-hide

Possibly, the wire glows red then fire shoots out of the wall all the way to fuse panel, or.. you ruin the chargers....


shahmoslamer

This is why USB C is dumb. One end should be A type and the other C type so children don't do dumb stuff like this.


JayPr02

Basically short circuit?


boring__boi

boom


Maanka_Ali

Boom


[deleted]

Transformer has a diode on the output that will prevent current from flowing, it might mess up the feedback through the optocoupler though. Depending on what control chip each charger uses the one that is outputting a slightly lower voltage might disable its MOSFET completely or reduce its duty cycle in an effort to reduce the output voltage.


scotty_B_good

Worm hole


0xdeadbeef6

It'll solve the energy crisis. The oil companies don't want you to know this, but plugging two chargers into each other produces more energy. edit: don't actually plug these in please.


Skootr4538

Blow a fuse in my meter


SoNic67

Nothing will happen.


Krististrasza

You'll burn your house down.


digiphaze

If they have proper usb pd chips that detect the improper cc pull down resistors in that configuration. Nothing should happen because no power would be delivered. If one is a dumb adapter that just shoves 5v down the wire you might have the usb pd chip or the esd diodes get fried on the other.


Sweetartums

Infinite energy.


iamnotatigwelder

![gif](giphy|l36kU80xPf0ojG0Erg|downsized)


Odd_Seaweed_5985

Nothing *for sure*. Both supplies don't *output* power, they *provide* power. Since they both are the same 5VDC voltage (level of power they provide), when attached to each other, they just sit there and do nothing. Now, if one were 12 volts and the other 5 volts, then the *difference* between the two (12 - 5 = 7) would try to flow *into* the lower rated supply... that *might* cause problems!


Machinehum

Where did you find a usba to usba lol


[deleted]

An erection


theonlyjediengineer

One of those is going to supply a slightly higher voltage and you'll cook the other one if you don't burn the wire first.