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Old 04-12-2008, 10:09 AM   #1
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12v Television or Inverter

Is there any benefit to trying to find a 12v LCD television and DVD player over just using a standard TV and player with a small, portable inverter? The small inverters are readily available and are inexpensive, while DC televisions and players seem to be an oddity in North America. Are there drawbacks to using and inverter that I may not be aware of? Also, what size would be suitable? A local store has 100W to 3000W inverters, so how do I know which would be big enough for what I need?

Thanks in advance!
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Old 04-12-2008, 11:06 AM   #2
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I kind of like things that multi-task (credit to Alton Brown). So I have a 17" Dell flat screen that has a power supply much like a laptop's. This kind of unit doesn't draw much power - I have used a 150w inverter. I now have a larger inverter -400w cheap from Costco - but the tv doesn't need it.

When we are not camping, I move the tv into our sunroom (that's the multi-tasking part).

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Old 04-12-2008, 11:38 AM   #3
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If you are going to buy a inverter why go small when you can for a little more money have something that you can use with more things?... I was told many years ago and would like to know if it still true or not..."The larger the inverter the less it needs to work the less draw on battery life"
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Old 04-12-2008, 12:00 PM   #4
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All electronic devices have power supplies that adapt an input voltage to the voltage(s) their circuits need. It is generally true that the more of the voltage adaptation going on, the less efficient the process will be. Therefore using an inverter, as one more voltage adaptation step, is less efficient.

In practical terms, the inefficiency loss isn't that much and there are compensating benefits. This is especially true given the fact that the efficiency losses are on a par with nominal variances in battery bank performance.

As for inverter sizing: there is some variance in efficiency over the range of power delivered but it usually isn't much for modern decent inverters. Generally you are talking 90% +/- 5% or so. So the factors in choosing inverter size generally have more to do with cost, quality, and input requirements.

True sine wave inverters are less efficient than stepped or pulse width inverters. Usually, a good stepped inverter will satisfy most needs with good efficiency but the prices of 2kw sine wave inverters aren't really that bad.

One factor with inverters is how they handle standby. This is often a significant efficiency concern. Good inverters can shutdown when not needed pinging the circuit to see when something has been turned on needing power. That saves energy.

Another factor is the ability to handle very small loads. Some inverters need a minimum load to work properly,

If you get a good quality inverter, you'll find these things specified. I had an old Trace 2kw inverter that was most efficient (95%) at 500 watts or so and needed 30 watts or so to come out of standby.

Once you get above a hundred watts or so, you need to start to worry about the link between the battery and the inverter and the battery's ability to deliver current. When the draw gets to a kilowatt or so it is time to start to be concerned about the impedance of the inverter feed, too.

Keep in mind that large currents and steady currents both have aggravated impact on available battery capacity compared to lower and less constant current draws. A typical group 27 AH rating is for about 5 amps steady for 20 hours. Double that current and the available energy capacity goes down by near 15%. That is why the DVD movie in the evening can have a drastic impact on how much battery you need.
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Old 04-12-2008, 02:49 PM   #5
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When you're on battery power, you really ought to keep your total power draw to 100 Watts or less. There are exceptions, of course, like if you're needing quiet time for two hours to watch the movie and you're going to start you genset first thing in the morning. But people who think 1000 Watt inverters are useful either have a multi-battery bank in their RV or they just like to buy new batteries real often.

A 400 Watt inverter is going to handle anything you ought to be doing, plus it will have a good low-draw idle (usually) mode. Don't even think of toasters and hair dryers!

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Old 04-12-2008, 02:56 PM   #6
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Quote:
Originally Posted by cameront120
Is there any benefit to trying to find a 12v LCD television and DVD player over just using a standard TV and player with a small, portable inverter?...
hi cam'

the primary benefit claimed for 12v rv/marine video gear is build quality...

jensen claims their units are better built for the mobile environment, which may/no be true or significant.

i don't see much evidence of higher failure rates on the sony/sharp lcd units commonly used in rvs...

and this might partially b related to how frequently consumers update these gadgets.

here are some relevant threads on this issue with links to 12v gadgets.

http://www.airforums.com/forums/f450...ion-31763.html


http://www.airforums.com/forums/f450...ion-30145.html

http://www.airforums.com/forums/f450...ter-35375.html

on the inverter side, i favor using smaller versions AT the outlets as needed.

xantrex, belkin, radio shack and others offer these small inverters in 100-200w sizes...

determine the power needs for the tele and use something with 20-30% more capacity...

the 19 sony is 80-90 watts so a 150 w inverter works well.

a tele with bulit IN dvd player is a nice idea but do you want standard or blu-ray dvd?

since i rely on a laptop/evdo card for communication on the road, the built in dvd player fills the 'movie' purpose,

and had the benefit of battery OR connected power. i carry extra batteries and have 12 hours or so of laptop juice.

i like the idea of an imac or win/pc 4 the all in one approach, but unless full timin' would hate to leave it IN the rv when not camping.

http://www.airforums.com/forums/f317...top-29406.html

cheers
2air'
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Old 04-12-2008, 03:31 PM   #7
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any benefit to trying to find a 12v LCD TV

Quote:
Originally Posted by cameront120
Is there any benefit to trying to find a 12v LCD television and DVD player over just using a standard TV and player with a small, portable inverter? The small inverters are readily available and are inexpensive, while DC televisions and players seem to be an oddity in North America. Are there drawbacks to using and inverter that I may not be aware of? Also, what size would be suitable? A local store has 100W to 3000W inverters, so how do I know which would be big enough for what I need?
Thanks in advance!
I am of the opinion that using a 12 volt TV is more efficient than going thru an inverter. If you put your hand on your inverter after it has been running for an hour, it will feel quite warm. This means that the conversion process is wasting some of the electricity as heat. Samsung and Panasonic make 12v TVs and there are probably others. My Panasonic is a Hi Def model FLM-1511 that draws 4 amps at 12V.

That said, I also carry a 150 watt inverter for other small applications like recharging electric toothbrush, razor, etc.
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Old 04-12-2008, 03:35 PM   #8
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But people who think 1000 Watt inverters are useful either have a multi-battery bank in their RV or they just like to buy new batteries real often.
Many folks find that heating a cup of coffee in the microwave or running a hair drier for a couple of minutes is no big deal as far as batteries go. A 2kw inverter properly wired can do this on a typical Airstream 2 battery bank without a hassle.

running the A/C is another ballgame, though.

In light of Joe's distributed power idea it should be noted that wiring resistance losses at 120v are quite a bit less than at 12v. That is an argument for putting the inverter close to the batteries and running a 110v trailer.
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Old 04-12-2008, 03:44 PM   #9
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Quote:
Originally Posted by Leipper
... wiring resistance losses at 120v are quite a bit less than at 12v. That is an argument for putting the inverter close to the batteries and running a 110v trailer.
which is an argument 4 battery powered toys n gadgets (without ANY wiring tethers) in the bedroom...

cheers
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Old 04-12-2008, 05:36 PM   #10
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My 17" LCD is placarded as 115VAC, 38 watts. My ancient Directtv receiver at 85 watts. Bought a 300watt true sine wave inverter and have been very happy with it. Runs the sat and the tv with plenty left over to recharge the laptop.

I actually use the inverter even when on shore power as the inverter output is cleaner than commercial power in a surprising number of places...

mike
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Old 04-12-2008, 06:45 PM   #11
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Thanks so much for the information all.

It looks like I have some reading to do in the links provided. Then we'll see if I actually understand any of it.
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Old 04-12-2008, 07:20 PM   #12
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Why not check out the selection at your local truck stop? They will have both 12volt tv's and dvd's, as well as some inverters. Even if you don't buy from them, at least you can see it and hold it in your hands, and read the fine print on the labels. And stuff that is built for "truck use" is usually pretty rugged, though not so much as marine.
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Old 04-12-2008, 08:13 PM   #13
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My notion of a truck stop is a service station with a diner attached. What you describe sounds like a store or such and I wouldn't even know how to find a truck stop as you describe it. Do we have those in Canada?
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Old 04-12-2008, 08:21 PM   #14
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Quote:
Originally Posted by cameront120
My notion of a truck stop is a service station with a diner attached. What you describe sounds like a store or such and I wouldn't even know how to find a truck stop as you describe it. Do we have those in Canada?
Good question. The one I am thinking of has multiple fuel pads, driver lounge, restaurant, and a small store to purchase things like tv's and dvd players, along with other trucker goodies. It seems you have some Flying J's up there, here's a link:
Welcome to Flying J Travel Plazas Website! Wi-Fi Hotspot Truck Stops
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Old 04-12-2008, 09:11 PM   #15
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I've never heard of Flying J. It looks like the ones up here are affiliated with Shell.
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Old 04-12-2008, 11:41 PM   #16
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Quote:
Originally Posted by n2916s
...I actually use the inverter even when on shore power as the inverter output is cleaner than commercial power in a surprising number of places...
Mike, very perspicacious of you.

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Old 04-13-2008, 12:42 AM   #17
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Quote:
Originally Posted by Leipper
Many folks find that heating a cup of coffee in the microwave or running a hair drier for a couple of minutes is no big deal as far as batteries go. A 2kw inverter properly wired can do this on a typical Airstream 2 battery bank without a hassle.

running the A/C is another ballgame, though.

In light of Joe's distributed power idea it should be noted that wiring resistance losses at 120v are quite a bit less than at 12v. That is an argument for putting the inverter close to the batteries and running a 110v trailer.
Leipper, not to make fun of other's attempts to live like home, but I notice you do alright making coffee on the galley stove in a pot for the Sierra Nevada Unit. It's better than most can make with a 120 volt drip coffee maker! Further Gail and I have three different ways of making coffee on our galley stove without AC, a Bialetti Mukka Express expresso maker, Aero-Express expresso maker and an old fashion blue enameled camp style percolator. I am reserving my AC appliances to those which can't be done on DC or the stove. We even have a 12 volt lunch-box cooker. Works great during the day when the solar is producing.
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Old 04-13-2008, 10:06 AM   #18
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not to make fun of other's attempts to live like home,
and I don't have a microwave or hair dryer in my rig, either. (See Coffee for what Don is talking about)

But I do note that many live differently than I and have different preferences. As I saw where this thread is going, I also saw that many that participate have a different point of view than others I encounter out in the wilds. So I let it go the direction this bunch chooses to take it (I do wonder about 2air and his toys, but I note he _is_ a playful guy ;-) ).

The fact is that it is much easier to find AC lights and appliances and gadgets for household electrical systems and they are often much less expensive than those you find in RV stores or truck stops for 12v. This means you have many more options in selecting for quality, cost, and features in the 110v arena.

I also note that the 12v wiring losses for a 100 watt load can easily exceed 5 watts in an RV. Upping the voltage by a factor of 10 reduces this loss by a factor of 100. That tends to allow for a significant compensation for any inverter losses.

The only downside to running a larger inverter is that it will cost a bit more. The upside is that it provides many more options and much more flexibility. It also tends to encourage proper wiring and installation which increases safety and reduces connection risks. (that doesn't mean it happens - I have seen a 4kw inverter under a couch wired with 20' of 10 gauge)

I may not now run such a system but I did 10 years ago when I needed to run a small office in the rig. I used a pair of AGM's to power a 24v input 2kw inverter. It did the job. (that was one heavy sucker of an inverter, too)

It rather bothers me to see the defensiveness to a suggestion about available choices here. Yes power supplies get hot. Yes you can abuse your energy availability. Yes you can choose to live a different way. Yes I am 'evaluating' the options rather than living them right now. Yes you can question my motives or experience if the forum rules don't bother you much.

But I wonder why not explore the idea a little bit rather than just trying to trash it? It seems unsafe in these forums to bring up any idea that doesn't fit the prevailing paradigm. I find that sad.
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Old 04-21-2008, 12:16 PM   #19
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Here is a link you might find useful:

TheInverterStore.com - Technical Support

I also called Aims and asked a few questions. Here is what they told me:

Q: What is the efficiency of an inverter?
A: Depends on the load requirement and inverter type. Inverters that do not supply a pure sine wave signal are often low efficiency because the parts of the signal that are not pure sine wave are not used. Some equipment is slightly more efficient using a modified sine wave because the circuitry is simpler. A pure sine wave converter is 90% to 95% efficient. If you apply a load that requires a pure sine wave to a modified sine wave converter, or even worse, a square wave converter, your efficiency can drop to 60% or less.

Comment: For my money a pure sine wave converter is the only way to go. These differences may explain the varying results that people have reported here.

Q: How should you size an inverter for best efficiency?
A: the Inverter will be most efficient at 1/3 the rated load. IE, for a 100 watt load, get a 300 watt inverter, but also make sure that any surge power at start-up is covered.

Q: Is the price of a digital pure sine wave inverter justified over the cost of an analog pure sine wave inverter?
A: in nearly every case, no. Get the analog unit.

Q: Do inverters still draw power when there is no load?
A: Yes. a small drain continues so for energy conservation, the inverter should be switched off when not in use.

One interesting side bar: I have heard people say that Honda generators rated at say 2000W are able to power equipment as large as cheaper generators rated much higher. I've always wondered why, but it turns out that the same principle applies about having a pure signal. You can generate a ton of wattage but if only a portion of the signal is usuable, Then the actual equipment you can run is lower. Hondas produce more usable power because they have a more expensive inverter system which produces a cleaner signal.

I'm not advocating either approach, but I'm going to try the standard electronics on an inverter for my full time AS TV/DVD. I put a meter on my system and it draws 52 watts. At 90% efficiency that is still only 57 watts or about 4 1/2 amps at the battery. It's a 19" Sharp LCD flat screen with a Sony DVD player. My opinion is that for a system that gets used alot like by fulltimers, you may be better off with 115V products. Higher voltage means lower amperage, which means less heat. Heat is a killer for almost everything electric. That's why 115V motors outlast 12 volt motors, and 220V motors outlast 115V units. For TV units that are used infrequently, the mode of failure is more likely to be moisture, vibration or other things that a 12V mobile ( marine) rated unit might endure better. I'm not so sure this question is purely black or white. More likely it depends on the environment and intended use. Just my thoughts on the matter. Life is an ongoing experiment.

I appreciate all the ideas presented. This forum has saved me a ton of money by informing me or just making me consider things I might have missed! Thanks!

David
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