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Old 02-01-2013, 10:17 PM   #1
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Simple inverter question

Okay, I know there a lot of inverter questions and replies with great knowledge but I have a hard time getting my head around some of that. I guess I am just looking for a simple answer on what size, as well as best brand, inverter to occasionally run my 19" LCD TV when dry camping. Mostly to watch morning news. I currently only have one battery that came with my TT but plan to add a second 12v this spring. I have a genny but would rather leave it off when not necessary.

Hopefully that is enough info and that I am not beating a dead horse here. Searching is great but sometimes threads go in wrong directions and hard to get specific answers.. so I'll just post a new one
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Old 02-01-2013, 10:21 PM   #2
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A small 300 or 400 watt inverter will power a TV or computer with ease.
BuyDig.com - Cobra CPI 480 - 400 Watt Power Inverter

Fuse the input wires from your battery.
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Old 02-01-2013, 10:29 PM   #3
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Herk, I saw that you were online and that was a fast reply!

I have a 12v cigarette lighter plug mounted in the wall right next to the LCD TV. The antennae boost is in the same fixture. I'd assume if I got an inverter with that adaptor I could just plug in there, correct?
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Old 02-01-2013, 10:36 PM   #4
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Quote:
Originally Posted by herk7769 View Post
A small 300 or 400 watt inverter will power a TV or computer with ease.
BuyDig.com - Cobra CPI 480 - 400 Watt Power Inverter

Fuse the input wires from your battery.
Funny, I just looked at that inverter at Amazon and was reading through the customer reviews. Most were good but this one reply kind of seemed knowledgable. He replied this...

"Power ratings are grossly over-stated. I have owned this product for about 1 year. It has worked great for powering my laptop while in the car. I have not been able to get it to supply power any greater than 100W without it shutting off however. With the inverter connected directly to clean battery terminals with the included battery clamps, vehicle running (14+ volts at clamps), I have unsuccessfully tried powering two different TV's rated at 140W. In both instances the inverter shut off when the TV's where powered on. I next tried turning on a 150W halogen flood lamp. The inverter shut down before the lamp lit. This inverter is rated at 400W RMS/800W peak. It should be able to supply these loads without any issues. Keep in mind I tried these loads with the inverter connected directly to my (dual) truck battery, engine running. The test where run on multiple occasions. There was no lack of supply current/voltage."

Just wondering if there is any salt to this.
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Old 02-01-2013, 10:56 PM   #5
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Herk, I saw that you were online and that was a fast reply!

I have a 12v cigarette lighter plug mounted in the wall right next to the LCD TV. The antennae boost is in the same fixture. I'd assume if I got an inverter with that adaptor I could just plug in there, correct?
Well, No.
The limit at 12 volts is 8 amps or 96 watts.

A 400 watt inverter needs to be fed with 33 amps and since the peak draw can go as high as 800 watts (provided the load stabilizes at 400 watts or less) it will need to be fused at 66 amps or less.

That is quite a bit higher than the 8 available at the cigarette lighter socket.

You will need to install the inverter close to the battery and hard wire it. You can run an extension cord to the appliance you want to use.

The wires from the battery to the inverter needs to be as short as possible for your installation and a minimum of 4 gauge battery wire.
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Old 02-01-2013, 11:13 PM   #6
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I have read some of what you replied with on other threads but why does the inverter come with a cigarette lighter adaptor? Does it behave differently when plugged in this way?
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Old 02-01-2013, 11:14 PM   #7
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Quote:
Originally Posted by Gregg Willow View Post
"Power ratings are grossly over-stated. I have owned this product for about 1 year. It has worked great for powering my laptop while in the car. I have not been able to get it to supply power any greater than 100W without it shutting off however. With the inverter connected directly to clean battery terminals with the included battery clamps, vehicle running (14+ volts at clamps), I have unsuccessfully tried powering two different TV's rated at 140W. In both instances the inverter shut off when the TV's where powered on. I next tried turning on a 150W halogen flood lamp. The inverter shut down before the lamp lit. This inverter is rated at 400W RMS/800W peak. It should be able to supply these loads without any issues. Keep in mind I tried these loads with the inverter connected directly to my (dual) truck battery, engine running. The test where run on multiple occasions. There was no lack of supply current/voltage."

Just wondering if there is any salt to this.
Here is the thing. I am sure his rant makes perfect sense from his perspective, but I can give you a reason why "his test" results could be skewed.

He does not say what size wire he used to connect the inverter to his batteries. at 150 watts (his lamp) is 150watts/12volts = 12.5 amps.
16 gauge wire is needed to avoid power loss in the incoming wires at that amp draw.

If his wires were too small, he would lose so much voltage the inverter would shut down.

How long were his leads from the battery in the running truck to the inverter? He does not say. Even wires of the correct gauge to carry that amperage need to be increased if the run is more than a few feet.

I have no reason to pick one over the other and there are several good inverters out there. (and some great ones)
Shop Power Bright 400 Watt 12V DC-AC Power Inverter at Lowes.com

You can also try a Pure Sine Inverter (plays nice with computer equipment)
https://www.google.com/#hl=en&tbo=d&...w=1735&bih=900'
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Old 02-01-2013, 11:15 PM   #8
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Quote:
Originally Posted by Gregg Willow View Post
I have read some of what you replied with on other threads but why does the inverter come with a cigarette lighter adaptor? Does it behave differently when plugged in this way?
It depends on how the socket is fused (accessory or cigar); not the inverter.

The amperage of the socket determines if the vehicle will blow a fuse or not.

Say the socket is limited to 10 amps @ 12 volts, then the maximum item you can plug in would be 120 watts.
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Old 02-01-2013, 11:24 PM   #9
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Thanks Herk. I'll look at that 12v face plate tomorrow and see if it has warnings, etc.

Could I not tap into the 12v wiring behind that plate if I needed to? I need the inverter on the counter underneath the TV so that it can be plugged into. I have a TT so battery is outside.
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Old 02-02-2013, 07:13 AM   #10
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Originally Posted by Gregg Willow View Post
Thanks Herk. I'll look at that 12v face plate tomorrow and see if it has warnings, etc.

Could I not tap into the 12v wiring behind that plate if I needed to? I need the inverter on the counter underneath the TV so that it can be plugged into. I have a TT so battery is outside.
I did not see any warnings on the plate; just in the manual for the plate.
Do you need the manual?

Short answer is "I don't recommend it"
Here is why:

1) That circuit may be fused behind the power center and hard to get to (mine is) and is small (10 amps).

2) The inverter needs to be as close to the battery as possible and keep it out of the rain.

3) The longer the run to the battery; the more battery current is wasted in the wiring and not getting to your TV. (this is not as big a problem in the 120 volt extension cord because on the high voltage side the current is 1/10th as high as the DC side.

120 watts required needs 120/12= 10 amps.
120 watts delivered supplies 120/120 = 1 amp
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Old 02-02-2013, 10:48 AM   #11
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Thanks Herk, that document is the same Winegard I have. Looks like a spring project. May be I can run some wire to a front closet, that would be as close to the battery as I could get and keep the inverter inside. Guess its not so simple after all.
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Old 02-02-2013, 11:46 AM   #12
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Quote:
Originally Posted by herk7769 View Post

...The inverter needs to be as close to the battery as possible and keep it out of the rain....
On my last 5th wheel I had an inexpensive 800w inverter to power the 22" TV and accessories such as a DVD player or satellite box. It worked fantastic, we could watch news in the morning and then 2-3 hours at night off of the dual 12v batteries. (We had solar panels too which would have the batteries back up by noon everyday.)

Herk is correct in that the inverter needs to be close to the batteries, run heavy wire from the batteries to the inverter and then go the distance to your TV with an AC extension cord.

I mounted mine in the front compartment so it meant going out to turn it on or off. There are some more expensive inverters that have a remote switch but this one did fine for me.

Our new Columbus 295 is coming with a generator but I plan on doing the same thing for it. I hate generator noise...
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Old 02-02-2013, 11:54 AM   #13
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I'm just throwing this out there since I'm not electrically "wired". I've used 2000w inverters (whole house) in my last two 5ers with great results. My neighbor did all the connections, I just ran the welding cable and wiring. Only used it for watching TV. Now just use quiet Honda genny.
Anyway, my neighbor is the electrical guy and he somehow wired his LCD TV in his boat to run on 12 volts. Not sure how he did it (he's moved), but maybe this is another option if TV is the only need.
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Old 02-02-2013, 12:22 PM   #14
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I purchase a Wagan Tech 3000 Watt Power Inverter from my local Costco for $299 that has a remote switch so it can be turned on & off from inside. It also has a 6000 watt peak rating and include the DC cables. I hope to install it when our Columbus arrives and I determine if it will fit in a suitable place.

It has 2 AC sockets for extension cords, etc. Plus a power block to run directly into the rigs AC circuits.

Besides space and location issues I would want to study the "modified" vs "pure" sine wave issue. Being a plug 'n play kinda guy, I want to know if the inverter is outputting clean enough current to run electronics safely...
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Old 02-02-2013, 12:42 PM   #15
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Nothing is ever simple.

As I posted in several other threads, "going big" when you are talking about inverters is never a good idea. For example, your 3000 watt continuous inverter when connected to a 3000 watt load will require 250 amps from your battery.

Due to the Peukert effect, the more amps you try to suck out of those thick lead deep cycle plates, the less sustainable capacity the battery has. In order to keep your supply constant, you should plan on never asking for more than 30% of a completely charged battery because that will reduce the capacity of the battery to 54% of its rating. (see graph)

(A 100 AH battery asked to deliver 30 amps will have an effective capacity of 54% or 54 AH. When you want to know how long the battery will last; you divide 54 by 30 and that is how long in hours the battery will last till the voltage drops below 10.5 volts - 1.8 hours)

To supply 250 amps for 1.8 hours @ 30 amps per battery will require 9 - 12 volt 100AH batteries.
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Old 02-02-2013, 04:22 PM   #16
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I did buy the Cobra CPI 480 400-Watt from Amazon. All I need it for is for morning TV watching when I don't have the gen. I'll install it in my basement in the spring. Thanks for everyone's input. As always, much appreciated.
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Old 02-02-2013, 04:42 PM   #17
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This is how I did mine
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Old 02-02-2013, 04:51 PM   #18
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Very professional install raceday! It looks like you have a dedicated battery. True?
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Old 02-02-2013, 04:55 PM   #19
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Very professional install raceday! It looks like you have a dedicated battery. True?
No just 2 deep cycle and the gray plug up top plugs into a bank of 20amp gel cells I made up if i need it, The little plug on the lower right is for a Battery Plus to keep them up and not have to run the onboard charger
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Old 02-02-2013, 08:47 PM   #20
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Nice! This is a model I will follow in the spring. Thanks for the photo's.
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