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Old 07-25-2015, 04:39 PM   #1
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Television 12 volt power use via inverter

How much power does the Television take at 12 volts?

I like to measure things, and have the equipment to do it in many cases. It has often been asked here how much power do things take from their battery. Here is some measurements I just did. I won’t bore you with the meters and stuff.

The Television is a Samsung 21” which came in my 2014 FC 20’. The DVD player is also a Samsung supplied with the trailer. The radio/sound system is the diabolical Sony which also was original.

The TV operates on 120 volts via a power supply velcro’ed to the rear of the set, which then supplies 14 volts DC to the TV via a special plug that is unique to the set. Thus, even if it would operate on 12 volts DC, I was not willing to modify the system to test it out.

The TV, on 120 volts grid power takes 20 watts with a stationary display test system I used. If that 20 watts came from 12.5 volts directly it would be 20/12.5 = 1.6 amps. (no inverter losses).

Since all inverters to produce 120 volts from 12.5 volts (realistic battery actual voltage) have conversion losses, I measured 3 different inverters and how many amps they took to run the TV.

The first inverter is a “modified sine wave” inexpensive Xantrex 400 watt unit. Cost was about $25 when I bought it.

The second is a Morningstar “true sine” 300 watt inverter costing about $225. It is the best small sine wave inverter I have found as it takes a minimal amount of stand by power, and also has a search function, which shuts it down until a 120 volt load is applied, then it automatically starts up.

The third inverter is the 1000 watt WFCO sine wave inverter which was an option I selected for my trailer when I ordered it. It works well, but has a very high stand by loss when running but no load is applied. Most all true sine wave inverters I have seen have similar high stand by losses, the Morningstar being the exception.

Results:

The Xantrex and the Morningstar inverters both required 2.1 amps to run the television. That means they were using 2.1 x 12.5 = 26 watts. (Watts = Amps x Volts).

So, there was a 6 watt penalty over line power of 20 watts for converting from 12 to 120 volts to supply the inverter losses. In amps, that is 0.5 amps extra.

The WFCO is a different story. To run the TV it took 3.73 amps or 3.7 x 12.5 = 46 watts. Over double the actual amount the TV requires on line power. In amps that is 1.6 amps more than the other inverters I measured.

The Samsung DVD player takes 4 watts on line power.

I put a DVD in and played a movie with very low TV speaker sound only.

Xantrex and Morningstar took 2.55 Amps or 32 watts for either one. So, the DVD added 6 watts via the inverter.

The WFCO took 3.85 Amps or 48 watts.

Then I turned on the 12 volt Sony radio sound system with the sub woofer, and figured out how to connect it to the TV (more head scratching, it is why I call it diabolical).

The Sony at 12 volts, the TV and the DVR together on the inverter, playing at moderate volume and powered by the Morningstar or Xantrex took 4 to 5 amps total. That depended on the volume and background music on “The Rose” video I had running. That is 50 to 67 watts drawn from the batteries. The WFCO would have increased that to 65 to 82 watts, or 5.3 to 6.5 amps.

Bottom line:

The TV operating on a cheep modified sine wave inverter, at low volume using the TV speakers does not take too much power. The Morningstar is very similar.

The same TV on the WFCO inverter takes a lot more for the inverter losses.

The TV plus DVD player and Sony Radio sound system can almost double the power with the modified sine wave or Morningstar inverter, and triple the power with the WFCO inverter.

Now you know more than you really care to know. LOL.
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Old 07-25-2015, 05:48 PM   #2
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Pretty cool info.
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Old 07-25-2015, 06:01 PM   #3
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That IS pretty cool


Shawn

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Old 07-26-2015, 09:45 AM   #4
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I don't waste my time or money with inverters. 12VDC all the way.
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Old 07-28-2015, 02:50 PM   #5
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Excellent information. That WFCO seems like a hog.
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Old 07-28-2015, 03:07 PM   #6
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It is not just the WFCO, but most pure sine wave inverters other than the Morningstar.

It seems to be a characteristic of the circuit design. Modified sine wave inverters are much lower in standby losses (current taken at very low loads and idle) than pure sine wave ones.

BTW, it is hard to find standby loss currents in the literature for a very large proportion of inverters. It is a number that is hidden or unstated, but I have measured enough or found the numbers often enough to be pretty confident of what I have said.
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Old 07-28-2015, 10:07 PM   #7
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Great post!! I wonder how a magnum would shape up. maybe Lew will chime in
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Old 07-29-2015, 04:34 PM   #8
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I have checked the Magnum. Their web site gives the standby specs, which is good. They show a 2 amp draw with no load, which is typical for most pure sine wave inverters. Similar to the WFCO and many others.

As I have mentioned above, it appears to be an electrical design issue for pure sine wave inverters. I don't know how Morningstar gets around it, but their standby loss is 0.4 amps when left on full time, and if you use the search function, it is much less as the inverter is only on for one cycle per second, while it looks for a load.
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Old 07-29-2015, 08:57 PM   #9
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My Samlex advertises a idle power draw of less than 0.5 Amps, from my experience this would be accurate.

http://www.samlexamerica.com/product...l.aspx?pid=499
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Old 07-29-2015, 10:32 PM   #10
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Quote:
Originally Posted by BoldAdventure View Post
My Samlex advertises a idle power draw of less than 0.5 Amps, from my experience this would be accurate.

600W 12VDC to 120VAC Pure Sine Inverter | PST-600-12
Yes, the spec sheet says <600 mA, which is 0.6 amps at 12 volts. Glad to see that they list the number. Thanks for posting.
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Old 08-03-2015, 04:54 PM   #11
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Then I turned on the 12 volt Sony radio sound system with the sub woofer, and figured out how to connect it to the TV (more head scratching, it is why I call it diabolical).

So how did you connect the Sony Radio to the Dvd/ Tv audio? I have not been able to figure this out! It'd be nice to watch a movie with better sound. Thanks!



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Old 08-03-2015, 06:54 PM   #12
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I've been looking at 12 volt TV with built in DVD players and think this would be the way to go ! Anyone use one?
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Old 08-03-2015, 10:02 PM   #13
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Quote:
Originally Posted by Racheli View Post
Then I turned on the 12 volt Sony radio sound system with the sub woofer, and figured out how to connect it to the TV (more head scratching, it is why I call it diabolical).

So how did you connect the Sony Radio to the Dvd/ Tv audio? I have not been able to figure this out! It'd be nice to watch a movie with better sound. Thanks!



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On the Sony press "source" to get CD, then press "mode" to get CD2.

Then write it down, because it makes no sense and you will forget how to do it, like I do.

Diabolical, absolutely makes no sense.
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Old 08-04-2015, 09:42 AM   #14
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Quote:
Originally Posted by derf View Post
I've been looking at 12 volt TV with built in DVD players and think this would be the way to go ! Anyone use one?
Yes, I've had one for several years and have been extremely satisfied. I'm also surprised at the number of people who waste money and energy using DC to AC converters.
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