Should I purchase an inverter

Hello All,
Outside of my initial introduction post, this is my first. I am contemplating purchasing and installing an inverter in our new RV. We will be mostly camping without shore power and would like the kids to be able to watch TV before bedtime occasionally without the generator running. The TV seems to have a really low amp draw and we have tandem 12V deep cycle batteries, so I am pretty confident that they should be able to handle normal/light use with an hour or so of TV occasionally before bedtime. My plan would be to make sure I run the generator at some point throughout the day to make sure the batteries have a nice charge at night.
Does anyone have a similar setup and have any recommendations for me? I'd like to keep it simple/affordable as we will really only be using it occasionally.
Thank you,
j12simm

Since it sounds like your primary consideration for an inverter is for TV viewing.  Know that some RV TV's are 12v, if that is the case for your rig, you would not need an inverter, at least for TV, so check to see if your TV is 12v.  In general the question to get an inverter or not, is dependent on what if any electrical appliances you need or want to run whilst away from shore power.  In our years of recreational RV'ing we never had or found the need for an inverter.  Now that we are full-timing the picture is different.

Thanks Gizmo. It seems to me like its 120. It will turn on when I have the generator running but not when we are running on 12V. I am not certain that we have a NEED for it, mostly just an opportunity to entertain our two little ones while Mom and Dad get to spend a little time together by the fire.
Do you know how would I find out if it is indeed 120 or 12?

I run a small (75W) inverter to run the bedroom TV and Wireless Joey. A larger (200w ?) inverter runs our front TV and Dish Hopper 3 system. Works great.
The small inverter I've had forever. I bought the larger one from Harbor Freight last year. Point is, these cheap MSW inverters work just fine and don't have to break the bank.

Tom

Welcome to the RVForum j12Simm. If the TV won't operate when you disconnect from shore power, or when the generator isn't running, that's a pretty good indication that it's a 120 volt (A/C) TV. Our first two motorhomes didn't have inverters, but they each had 12 volt (D/C) TVs, so it was no big deal. Our current motorhome has a large inverter that powers several A/C outlets in the coach, but it draws a lot of power too.

If you're looking for an inverter that will power a typical flat screen TV in an RV, a low wattage inverter will work fine. Just don't make the mistake of buying more inverter than you need. Inverters are only about 85 to 90% efficient and they consume power as well. Larger inverters will draw your batteries down faster.

A 12 volt TV is another option, and you can find them up to about 32" in screen size. Some have integrated DVD players. Your kids may prefer to watch their own shows on tablets, and as with 12 volt TVs, you wouldn't need an inverter at all. Just something to consider.

Kev

My TV is a regular residential model that happens to be 12 volt DC. It uses a power brick for 110 volt AC.

You should be able to look at the input power source on the TV. If it has a regular 120v power cord that plugs into a regular outlet and then enters into the TV, it's ac powered. A 12 volt system would have a 12 volt power cord that is plugged into a 12 volt socket from the RV or from a small 120 ac to 12 volt dc "brick". I just finished installing a 1500 watt pure sine wave inverter in our RV dedicated to powering a 120 volt powered oxygen concentrator  for use at night with my wife's CPAP. Our battery bank consists of four 6 volt GC2 batteries rated at slightly over 200 amps each. These are true "deep cycle" batteries. I'm installing four 100 watt panels on the roof to recharge these batteries. You may consider using, if you are camped, a set of portable panels to help recharge your batteries during the day, rather than the genset. If you have room, you may also think about using two 6 volt "deep cycle" batteries rather than the two 12 volt batteries you're considering.

Kevin Means said:

Welcome to the RVForum j12Simm. If the TV won't operate when you disconnect from shore power, or when the generator isn't running, that's a pretty good indication that it's a 120 volt (A/C) TV. Our first two motorhomes didn't have inverters, but they each had 12 volt (D/C) TVs, so it was no big deal. Our current motorhome has a large inverter that powers several A/C outlets in the coach, but it draws a lot of power too.

If you're looking for an inverter that will power a typical flat screen TV in an RV, a low wattage inverter will work fine. Just don't make the mistake of buying more inverter than you need. Inverters are only about 85 to 90% efficient and they consume power as well. Larger inverters will draw your batteries down faster.

A 12 volt TV is another option, and you can find them up to about 32" in screen size. Some have integrated DVD players. Your kids may prefer to watch their own shows on tablets, and as with 12 volt TVs, you wouldn't need an inverter at all. Just something to consider.

Kev

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Kevin makes excellent points here, especially with not buying more inverter than you need and maybe consider replacing your TV(s) with 12v models.  If you do elect to purchase an inverter spend the extra dollars on a pure sine wave which will be kinder to your electronics.

Heli_av8tor said:

I run a small (75W) inverter to run the bedroom TV and Wireless Joey. A larger (200w ?) inverter runs our front TV and Dish Hopper 3 system. Works great.
The small inverter I've had forever. I bought the larger one from Harbor Freight last year. Point is, these cheap MSW inverters work just fine and don't have to break the bank.

Tom

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Tom, are you powering your computer on the Harbor Freight inverter?  I've read that the MAC desktop doesn't like the modified sine wave.  I'm still vacillating between pure and modified. 

Gary

PS.  glad your trip went well. 

Do you know how would I find out if it is indeed 120 or 12?

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You already did and it's 120v.  However, there is a slim possibility that you could eliminate the tv 120v power cord and connect it direct to 12v. If it has a "wall wart" (transformer module) in the power cord, it may be able to run on 12v (but even then it's just one of several possibilities). 

Gary:  Yes. And I've not had problems running anything on MSW. Even the Dish Hopper 3, which was said to be power sensitive, hasn't had a problem with MSW.

What a trip it was...

Tom

Thank you all for the input. I'll talk this over with my wife and decide what we want to do.

Justin: Be aware that the low tv amp draw is @ 120v. To produce that same amount of power @ 127, the inverter has to draw more than 10x the 120vac amps. So. 1A at the tv means 10-11 amps from the batteries.  Your two 12v batteries probably have a usable 80 amp-hours, which should be plenty to run a modest size LCD tv for a few hours, but using an inverter for anything really sucks the amps from a battery.

Heli_av8tor said:

And I've not had problems running anything on MSW. Even the Dish Hopper 3, which was said to be power sensitive, hasn't had a problem with MSW.

What a trip it was...

Tom

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This may or may not be true.  A MSW will generally power all the electronics and in doing so may lead one to conclude the MSW inverter is fine.  However the issue is not whether it works when you install and turn it on, the problem is over time, where sensitive electronics running on a MSW inverter can and do loose performance and likely die an early death.  Unless one is only powering those electronics that are unaffected by MSW inverters, considering the cost of modern rigs and the electronics that come with or added to them, I would argue a PSW inverter is worth the extra dollars.

Another tip: when you install your inverter, even if it's a small one, it's best to mount it close to the batteries to keep the length of the 12 volt wiring as short as is practical, then extend the 120 volt wiring to where you want to use it.

All inverters have a low voltage cutout, where they stop working once the input voltage drops to that point.  If you have a long wire run on the 12 volt side, the voltage at the socket will be less than the battery voltage, so as the battery starts to discharge the inverter will shut down earlier than it should.

Keeping the DC wiring short minimizes the wire loss, so the inverter will run until the battery is actually drawn down to the cutoff voltage.

I haven't seen a computer or other sophisticated electronic device struggle with MSW since around year 2000. Nor a "wall wart" charger or transformer module either. But there are still some types of devices that don't play well and suffer over the longer term.  Motors and compressors are the biggest example, but things like electric blanket controls, digital timers, and X10 power management devices are problematic. You can get them in designs that work fine, but the typical one does not. With the price of PSW falling rapidly, there is little reason not to choose it if buying new.

Gizmo said:

the problem is over time, where sensitive electronics running on a MSW inverter can and do loose performance and likely die an early death.

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Not to be confrontational, but is this documented or is it something that's been repeated enough that most just accept it?

Tom

Heli_av8tor said:

Not to be confrontational, but is this documented or is it something that's been repeated enough that most just accept it?

Tom

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The only thing that I've found are anecdotal comments from owners of Mac computers.  Mine is a $2,000 desktop and I prefer not to have to replace it prematurely.  But I haven't found anything from an actual Apple source which states running a Mac on a MSW Inverter will shorten its life.  That said, I don't really want to find out the hard way.  I'd love to hear from other Mac users if they're using a MSW Inverter. 

Heli_av8tor said:

Not to be confrontational, but is this documented or is it something that's been repeated enough that most just accept it?

Tom

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No it is not an internet myth, this is one of many articles addressing this.  https://www.altestore.com/blog/2015/10/pure-sine-wave-vs-modified-sine-wave-whats-the-difference/

That's an excellent article, but it reinforces just what some are saying here: only some specific types of electronic equipment are affected, including just "a few laptop computers".    Nobody disputes that PWS is preferred, but it can be argued that the risk is not as great as some would have it. However, for zero risk, PSW is the only way to go.

Fifteen years ago damage from MSW inverters was not uncommon, but with the increasing use of inverters in cars, boats and off-grid homes, circuit board designers have largely learned to cope.

In my own extensive experience using MSW inverters with all sorts of electronic and other gear, I've lost  a couple of X10 modules, a couple digital timers, and an electric coffee maker with digital timer controls.  All of them back around 2000-2005, though we've learned to avoid certain brands of coffee makers (the brands that seem to work ok on MSW are Mr Coffee and Black & Decker). Have never had a computer or printer or scanner problem in 18 years of inverter use, but I've never owned a Mac either.

Some other things I've learned is that most speed control devices (e.g. many sewing machines) and electric blanket/pad controls won't work and may well be damaged. There are a few specific brands of each that are ok, but the general rule is don't use them on MSW.  Also, most digital clocks will gain or lose time when on MSW. Sometimes rapidly, like 5 minutes/hour.