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UltArc 09-10-2013 11:55 PM

Weird Home Electrical Question. DC & AC
 
Alright guys, this is going to sound a bit strange. (Hey, it says way off topic)

What happens if an AC appliance, TV, game system, microwave, were to come in contact with DC (specifically car) battery terminals?

I know, it's not a good idea. I know, it won't really fit, I know, it's ridiculous. But for informational and a small wager (not mentioning my position), what would occur to the AC appliance? There was a lot of time on two devices searching for the answer, but as we puzzled Google, nothing was found to help answer.

jeff88 09-11-2013 12:03 AM

I would imagine if you hook up an AC appliance to a DC power source, it would eventually blow the item, possibly a small amount of smoke or maybe catasthrophic, video worthy failure.

Try going to physicsforums.com to find an answer.

Ryland 09-11-2013 12:09 AM

first off, as the voltage drops (brown out) the amps goes up as it's drawing the same number of watts, as the number of amps goes up the smoke starts to come out.
stuff with transformers will heat up slowly until it starts to smoke, stuff with lighter weight electronics will most likely smoke faster.

short answer is that it will get really smokey in your house.

jamesqf 09-11-2013 02:08 PM

It's really going to depend on the appliance. Something like a toaster would sorta work, depending on power levels. Even some motors might - I've read this, anyway, but haven't tried it. Things with transformers won't. But the odd thing is that a lot of the transformers, particularly the "wall wart" sort, are converting the household 120 volt AC to DC, usually at 9 or 12 volts, so with the right plug (and maybe a resistor) you can run them directly on 12V DC.

UFO 09-11-2013 03:54 PM

It depends on the battery voltage, but 12V DC will not even power up your 120VAC stuff, let alone draw enough power to blow stuff up. The switching supplies in your wall-powered electronics have under-voltage lockout (UVL), so they will not even try to power up. Toasters and such will not have enough voltage to make the heat or draw significant power.

Your stuff will NOT smoke.

UltArc 09-11-2013 06:23 PM

Now of course one would use an inverter, and would need a power source to keep the battery going, but the question was specifically what would happen if a tv was connected to a DC battery, one prong to positive, the other to the negative.

One individual said nothing would happen, the other said it would destroy the tv.

I am getting mixed signals from the responses :/

Ryland 09-11-2013 08:56 PM

Quote:

Originally Posted by UltArc (Post 390059)
One individual said nothing would happen, the other said it would destroy the tv.

I am getting mixed signals from the responses :/

It depends on the TV and the type of power supply that is in it.

either way it's not going to work, so why bother with finding out if it will destroy stuff as well?

UltArc 09-11-2013 09:09 PM

Quote:

Originally Posted by UltArc (Post 389880)
I know, it's not a good idea. I know, it won't really fit, I know, it's ridiculous. But for informational and a small wager (not mentioning my position), what would occur to the AC appliance? There was a lot of time on two devices searching for the answer, but as we puzzled Google, nothing was found to help answer.

Nothing so far has satisfied or proven either of our takes on it lol

I don't have any frustration for that, I just thought some one here may have a resource that would point us to it. I thought for sure the internet would be filled with people making poor decisions like this! But maybe that supports the view that nothing would happen to the device.

Xist 09-11-2013 09:34 PM

Quote:

Originally Posted by UltArc (Post 390059)
Now of course one would use an inverter, and would need a power source to keep the battery going, but the question was specifically what would happen if a tv was connected to a DC battery, one prong to positive, the other to the negative.

One individual said nothing would happen, the other said it would destroy the tv.

I am getting mixed signals from the responses :/

There are thrift stores, you know? :D I was told that old televisions go for a dollar.

Jack-MTL 09-13-2013 01:25 AM

Quote:

Originally Posted by UltArc (Post 389880)
Alright guys, this is going to sound a bit strange. (Hey, it says way off topic)

What happens if an AC appliance, TV, game system, microwave, were to come in contact with DC (specifically car) battery terminals?

I know, it's not a good idea. I know, it won't really fit, I know, it's ridiculous. But for informational and a small wager (not mentioning my position), what would occur to the AC appliance? There was a lot of time on two devices searching for the answer, but as we puzzled Google, nothing was found to help answer.

Hi, I studied electrical engineering in college so I can tell you a few things about that.

Most of the AC appliances have transformers in them, transformers will be the exact equivalent of a long wire when DC is applied. No power at all will make it to the appliance side. If you have a strong battery, like a car battery, and small wire with not too much resistance, you will just fry the wiring in the transformer.

Anything with an electronic power supply will simply not power up because 12V is way too far below what they need to work.

I would guess that very few thing would be badly damaged, or damaged at all actually. However, if you started to put several batteries or a Hybrid battery-pack at 144V or 250V DC, then I would strongly suggest to take cover, sparks will be abundant!

If you get a multimeter and check some power outlets, I'm sure you could find a few of them with already a DC bias, they will read 120V on AC and 3-4 V on DC, probably not 12V, but it's not a big difference for anything designed to take 120V AC.

H-Man 09-17-2013 06:30 PM

A laptop AC adapter or similar will run on high voltage DC provided that the rectifier bridge is up to the task of dealing with 100% duty cycle on half the diodes, the input voltage is within specification (144vdc should work on a power brick that can handle 110-220vac,) and that it is a SMPS. A SMPS will actually convert AC to DC before converting it to a lower voltage. A traditional transformer based supply needs AC or rapidly pulsed DC current to work, DC off of a battery will not power it.


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