Run 12V TV/monitor off of 12V outlet or via inverter? - Fiberglass RV


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Old 11-10-2016, 12:34 PM   #1
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Run 12V TV/monitor off of 12V outlet or via inverter?

A newbie question, I'm sure.

We'll pick up our Escape 19 this summer, so I've mostly been lurking, doing research, learning as much as I can from all the incredibly knowledgeable people on this forum. In doing so, I came up with a question:

I happen to have a computer monitor/display that comes with an AC power supply, but the pwr supply actually steps it down to 12V (not sure of amperage yet). So, assuming the amperage works out, would it be best to run it in "AC" mode, plugged into the trailer's inverter or, since it really just needs 12V to begin with, would it be better to run it directly from a 12V receptacle?

I would assume that if you run via an inverter, there's a certain amount of overhead (heat dissipation, etc.) that takes place if you run something off an inverter -- and then again when it hits the monitor's power supply. Seems like running it directly (again, assuming the amperage is a match) would be the more efficient approach.

Then again, I barely made it through Electric Shop. Can you tell?
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Old 11-10-2016, 12:42 PM   #2
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Most lap top computers have a "car charger" available. I suggest that you use the "car charger" made for your computer.

FYI, Most laptop computers run on 19VDC.
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Old 11-10-2016, 01:17 PM   #3
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[QUOTE=Rod Scher;616491]A newbie question, I'm sure.

...So, assuming the amperage works out, would it be best to run it in "AC" mode, plugged into the trailer's inverter or, since it really just needs 12V to begin with, would it be better to run it directly from a 12V receptacle?
.../QUOTE]

Does your trailer have an inverter? You mention "the trailer's inverter" so I suppose so.

There are losses incurred every time you convert voltage from one level to another. Losses associated with the inverter piled on top of the losses from the "brick" converting it back to 12v.
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Old 11-11-2016, 11:11 AM   #4
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Run 12V Monitor Directly from 12V Source

Sounds like you're both saying essentially the same thing, then: Assuming that the voltage and amperage is a match, then more efficient to run that monitor directly from some source other than an inverter + the display's power supply, since that would involve two different conversion instances, with some waste at each point.

Thanks for the feedback!
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Old 11-11-2016, 11:54 AM   #5
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Byron has the totally sensible answer. Use the computers 12 VDC cigarette plug in cord. It supplies 12VDC directly to the computer provided you plug it into the right socket on the computer.
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Old 11-11-2016, 12:13 PM   #6
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12V Display

Exactly -- although it's not the computer I'm trying to power. (I will be, of course, that's just not what I'm asking about at the moment.) My question was specifically about powering a (supposedly) 120V monitor -- which happens to really be a 12V monitor, when you look closely at it.

But yep, that's how I'll power the computer, alright!
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Old 11-11-2016, 12:19 PM   #7
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We do just that. The power pack will tell you the polarity for the 12 volt cord. Works great. No sense wasting the losses in the inverter and power pack.

John
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Old 11-11-2016, 12:21 PM   #8
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I have a small flat screen TV that happens to be 12V but came with a 120V power supply and AC plug. I have not as yet found a suitable 12V plug but plan on doing so in the event I want to run it on 12V without an inverter. That said, the amperage for this device is so low as to make any losses from the up/down conversion running through an inverter pretty low as well.
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Old 11-11-2016, 12:24 PM   #9
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Great - thanks! Good to know.
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Old 11-11-2016, 12:39 PM   #10
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Raido Shack
https://www.radioshack.com/collectio...nt=20331737669
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Old 11-11-2016, 12:43 PM   #11
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Make sure you choose the correct polarity for the item you are charging. Takes a fraction of a second to fry electronics if you choose the wrong one. I have personal experience using a similar Radio Shack charger ( had about a dozen tips ).

https://en.wikipedia.org/wiki/Polarity_symbols
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Old 11-11-2016, 12:45 PM   #12
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120V/12V monitor

Oh, man, I'd forgotten about those Radio Shack connector kits! Used to have one; wonder if I've still got it tucked away somewhere. Thanks for the reminder - that'd be very handy. If I can't find mine, might have to order one.
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Old 11-11-2016, 12:47 PM   #13
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Thanks for the polarity info - might not have thought about that!
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Old 11-11-2016, 01:00 PM   #14
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I have a small flat screen TV that happens to be 12V but came with a 120V power supply and AC plug. I have not as yet found a suitable 12V plug but plan on doing so in the event I want to run it on 12V without an inverter. That said, the amperage for this device is so low as to make any losses from the up/down conversion running through an inverter pretty low as well.
We have a tv that works on 120 and 12V. I'm sure the 120 power pack steps it down to 12V. We got a 12V cord that plugs into the cigarette lighter power supply in the Casita. We can watch the news at least even when dry camping. When plugged into shore power we use the 120 power supply. You have to have the correct 12 V cord to fit your TV or it can damage it. I'm not sure I'd want to use a multi fit kit because several of the pieces can fit the tv as we found out.
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Old 11-11-2016, 09:25 PM   #15
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I have a small flat screen TV that happens to be 12V but came with a 120V power supply and AC plug. I have not as yet found a suitable 12V plug but plan on doing so in the event I want to run it on 12V without an inverter. That said, the amperage for this device is so low as to make any losses from the up/down conversion running through an inverter pretty low as well.
I power a small flat screen TV and a docking station (for my XM radio) directly off the 12 volt system in my Scamp. The hard part is finding a cable with the proper size plug to plug into your device. You can always cut and reverse the wires if the polarity is reversed, be sure to check the polarity with a meter before you attempt to power your device. Many of the new electronics will refuse to accept power if the voltage or polarity in incorrect but don't count on that to protect your devices.
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Old 11-12-2016, 02:19 AM   #16
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If you're going to use an inverter look at specifications they should tell you the efficiency in percentage. The best you can probably hope for is 95% which means that there's 5% of the power going up in heat.
Good luck.
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Old 11-12-2016, 06:43 AM   #17
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For myself, when looking for a 12v power source I look for the term "regulated" or some such term in the specs. This tells me the power source will put out only 12vDC even if the plug finds 13.5vDC due to battery charging going on. Most 12v devices tolerate a range of voltages centered around 12v, but a TV or other sensitive electronics might not be tolerant of a the higher charging voltage if it was designed with the expectation of getting just 12vDC from a power brick.


I may be overly finicky, YMMV.
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Old 11-12-2016, 06:55 AM   #18
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... other sensitive electronics might not be tolerant of a the higher charging voltage if it was designed with the expectation of getting just 12vDC from a power brick.
Or the AC ripple from a cheaper converter... not all DC power is created equal. Not all DC power sources are pure direct current. Not all sensitive electronics play well with unregulated and/or poorly filtered DC supplies. YMWV (Your milage WILL vary).
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Old 11-12-2016, 11:18 AM   #19
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Or the AC ripple from a cheaper converter... not all DC power is created equal. Not all DC power sources are pure direct current. Not all sensitive electronics play well with unregulated and/or poorly filtered DC supplies. YMWV (Your milage WILL vary).


I thought the same thing. Does anyone know where to get a 12v filter that would ensure clean power for electronics?
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Old 11-12-2016, 11:23 AM   #20
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I thought the same thing. Does anyone know where to get a 12v filter that would ensure clean power for electronics?


As long as the trailers power system has a decent battery the 12vdc should be fine for the TV direct connection to the trailers 12vdc.

Do be sure of polarity though or you might let the smoke out!
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