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Old 12-10-2008, 08:20 PM   #1
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the straight inverter poop?

I have a inexpensive modified sine wave 400w inverter I plugged a 19" Sharp LCD and it seemed to work fine. In reading the inverter instructions, in small print, hidden away in the back was "check with appliance manufacturer that appliance is compatable with a modified sine wave inverter" so I did. I asked "Is your model LC19DV24U compatable with a modified sine wave inverter"

They sent me the answer "we do not recommend inverter use for any of our televisions" not saying why. sooooo..... I asked them- "why do you not recommend using an inverter" and also asked if they would recommend a pure sine over a modified sine inverter.

They answered again "any alteration will void the warranty and can damage the unit". Never did say how or why. Also never gave me a hint about my question about using a generator. I gave up on them.

Is this a CYA answer or what? Is there a real reason I should not use a LCD TV with an inverter? What about generators? I have a Honda 2000si
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Old 12-10-2008, 09:39 PM   #2
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I have a inexpensive modified sine wave 400w inverter I plugged a 19" Sharp LCD and it seemed to work fine. In reading the inverter instructions, in small print, hidden away in the back was "check with appliance manufacturer that appliance is compatable with a modified sine wave inverter" so I did. I asked "Is your model LC19DV24U compatable with a modified sine wave inverter"

They sent me the answer "we do not recommend inverter use for any of our televisions" not saying why. sooooo..... I asked them- "why do you not recommend using an inverter" and also asked if they would recommend a pure sine over a modified sine inverter.

They answered again "any alteration will void the warranty and can damage the unit". Never did say how or why. Also never gave me a hint about my question about using a generator. I gave up on them.

Is this a CYA answer or what? Is there a real reason I should not use a LCD TV with an inverter? What about generators? I have a Honda 2000si
It is a CYA answer. The modified sine wave inverters have harmonic distortion problems with their output, which can cause many problems with electronics equipment. Due to the very high harmonic content of the chopped sine wave, you can get everything from distorted pictures to weird tones from the speakers. Most modern electronics have very marginally designed power supplies that do a less than stellar job of filtering the supply voltage. But face it, AC from the wall is really pretty good. So if it works with your equipment use it. However, check it the equipment you have plugged into the inverter for excessive heat and never leave it running unless you are present.
The Honda EU2000i generator has a very clean sinewave output. I took mine into the shop at work and put it on a piece of Power Quality Measuring test equipment. The test equipment could read no real distortion from the generator. We also tested the line regulation and found the output voltage to vary less than 1% up to full load.
In other words I would trust this generator with my life.
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Old 12-10-2008, 10:20 PM   #3
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Both my Honda 2000i and my pure sine wave inverter put out power that is extremely clean and I would plug anything I own into either without a second thought. I am not so sure I would feel the same way about the "modified" sine wave inverter - generally decent frequency stability but all that noise...

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Old 12-10-2008, 10:21 PM   #4
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Gary - That was great information, and it certainly increased my awareness about how I have been using my inverters. I have two Xantrex 400 watt modified sine wave inverters that I have used extensively to power my laptop and, to a lesser extent, the 15" Sharp Aquos LCD television that came with my Bambi. Fortunately, so far, I haven't experienced any of the picture distortion or hum from the speakers. However, I am considering upgrading to a bigger HDTV and, based on what I've read, may consider investng in a true sine wave inverter. Something that may be worth noting is when I tested both inverters (identical models) on an accurate voltage meter, one read 130v, and the other was 118v.

Here is a FAQ from the site of the manufacturer that I found useful:

Xantrex Technology Inc. - FAQ
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Old 12-10-2008, 10:57 PM   #5
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But face it, AC from the wall is really pretty good
have you ever looked at it? not a pretty sight. That's why autoformers and surge suppressors have such a good market.

To rephrase the original question to gain some insight, replace "inverter" with UPS.

Nearly all of the UPS's you get at retail advertised for computers and home theater systems use MSW inverters.

You should note that there are a number of different techniques that fall into the modified sine wave category. Some work better than others. A good MSW is more efficient than a so-called true sine wave inverter and there are very few modern 110VAC devices that cannot operate safely with one.

Note that the real problem isn't interference but rather heat. If indeed the inverter is going to cause damage, it will usually do so by creating excess heat in the device being powered's power supply.
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Old 12-11-2008, 04:47 AM   #6
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In other words I would trust this generator with my life.
That's a pretty strong endorsement.

How about this: You are thrown overboard in the middle of the ocean. I can throw you a life preserver or a Honda EU2000i. Would you still trust the generator?
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Old 12-11-2008, 07:34 AM   #7
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I am considering installing solar - two panels what inverter should I add?

Could you recommend an additional inverter to add to the solar panels? I currently have one in the Safari, however I am limited to only two plugs.
One located at the TV and one near the stove.

Please suggest some "brands or types" of inverters to start researching.

Many thanks,

Lin.
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Old 12-11-2008, 11:18 AM   #8
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Could you recommend an additional inverter to add to the solar panels?
If you really want to do it up right, put a decent 2kW to 4kW inverter between your breaker box and power input connector. It would be nice to be able to bypass the AC circuit but otherwise, a good inverter that can handle most appliances can be a good way to go.

Such an inverter can cost towards $2k and will need 'pro grade' wiring. It should be placed as close as possible to your battery bank and use really heavy wiring and fuse.

A solar or alternative energy vendor should be able to help you find a good inverter. Top brands include Xantrex and Magna (where's BestConverter Randy? ;-))

I'd like to see a power sharing device like Victron Energy - Phoenix MultiPlus 12 / 24 / 48 Volt - Phoenix MultiPlus Compact 12 / 24 Volt does - the better inverters will detect a source load that is failing (like an overloaded genset) and swtich over quickly but the Victron actually shares the load.

Keep in mind that one 60# (group 27 size) battery is only good for watching one movie on a home theater system in your RV. The idea of the larger sized inverters is to be able to handle short term peak loads rather than continuous loads. Your big limitation in a travel trailer is going to be the 10 watt hours of usable energy per pound of battery bank.
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Old 12-11-2008, 12:48 PM   #9
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With new flat screen high definition TVs being more akin to computers than to the old TVs, I chose a pure sine wave inverter to run our Vizio and our satellite box in our Caravel. The inverter system is completely separate from the shore power system. Separate outlets. 12v power is supplied by two Trojan 6v deep cycle batteries.

Sure, the pure sine wave inverter is more expensive, but you are not doing a fleet, only one trailer.

We have used this system dry camping many times with no problems.

I would never hook anything I love up to questionable power, and I consider modified sine wave power, questionable power.
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Old 12-11-2008, 01:42 PM   #10
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I don't think a pure sine wave inverter is in Santa's sleigh, this year anyway.

We are not into a lot of technology when camping, but do want to watch a DVD or 2 or 3 when the grandkids are with us. Our camping TV right now is a Sharp TV/DVD player that draws, if I figured it right, 1/2 amp. So far I only used it once and then after 20 minutes the modified sine wave inverter alarm went off saying the voltage was too low. But, while it was working it seemed fine, no video or audio interference. I guess I can keep a close eye on it to see if it is overheating. Do you think this would be OK? Or, I can always play it safe and hook up the Honda.

The low voltage alarm going off makes it look like I need a new battery. I will probably upgrade to at least 2, and may want to get rid of the old Univolt while I am at it.
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Old 12-11-2008, 02:35 PM   #11
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it is really amazing how the "pure sine wave" and "Trojan deep cycle 6v golf cart battery" mantras keep distracting people from the core issues (and their money).

If your device works on the inverter and there isn't any smoke or other indication of excess component heating (i.e. smell) and it is a device you'd plug into a UPS, then you should be OK. Nearly all inverters except for the truly cheap ones are intended for use to supply entertainment equipment and do quite well in that service. Read your inverter manual and it should provide the appropriate caveats and concerns.

A half amp at 12v is only 6 watts. At 120v it is 60 watts so you need to always think amps with volts and that is easiest if you just use watts. A 3 hour viewing session would use 180 watt hours (this is rather low as many TV's often use more than that themselves, even laptops often run 90 watts). Most people watch movies when it is dark and will have a light on too. That adds another 20 to 50 watts (or more).

This is a steady drain at moderate power levels and that works a battery rather hard.

The typical 60# battery (either group 27 or T105 sized) has about 600 watt hours usable energy capacity. So the 180 watt hours should use about a third of its available capacity. That is about a sixth of the capacity of the typical 2 trailer battery bank and is a very low estimated movie watching estimate.

If you do not have your inverter close to the battery with heavy duty wiring and good connections, a low voltage alarm may be telling you not only about the battery but also about the drops in your wiring. See Wire size considerations for some ideas on how much wiring can cause problems.

Let your battery rest for a half hour or so then check its voltage. If it is above 12.0v it just needs a charge (below that voltage the charge is needed like right now). Experience will be your best guide as to what you can expect from your battery banks.
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Old 12-11-2008, 07:22 PM   #12
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If you do not have your inverter close to the battery with heavy duty wiring and good connections, a low voltage alarm may be telling you not only about the battery but also about the drops in your wiring. See Wire size considerations for some ideas on how much wiring can cause problems.

Let your battery rest for a half hour or so then check its voltage. If it is above 12.0v it just needs a charge (below that voltage the charge is needed like right now). Experience will be your best guide as to what you can expect from your battery banks.
My old Uni puts out a purdy steady 13.9 to 14v.
After sitting a couple of days I used the hydrometer ( I used for the first time) and got readings of:
1250 1250 1200 1225 1200 1225
I charged for about 6 hours and then got:
1250 1225 1200 1225 1200 1225

Right after charging the battery voltage was 12.25v ( with 2 12v ceiling lights on)

Did I mention I don't know what I'm doing? But as far as I can tell from the stuff I have read I think that means this battery is marginal at best. Agree?
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Old 12-11-2008, 08:06 PM   #13
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After sitting a couple of days I used the hydrometer
this is another one ... I do not recommend any use of a hydrometer in modern batteries for RV service. Voltage will tell you enough.

The old Univolts are not battery chargers.

6 hours isn't enough to charge a battery, even with a decent modern 3 stage charger. Your specific gravity readings indicate that the battery didn't get hardly any charge at all.

a couple of 12v lights can put quite a load on the battery. 12.25v with this kind of load indicates the battery is doing OK. Take the load off and you'll probably see the voltage rise up to maybe 12.4v or even 12.6v over the period of an hour or so.

These topics tend to generate discussions by people who know things with a certitude I wonder about. So I better get outa' here while I still have my skin. Search the Zephyrs blog where the wire size entry was for more about batteries, hydrometry, and links to many many resources.
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