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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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Quote:
Originally Posted by Gregg Willow View Post
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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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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