No 12 volt cigarette outlet

[rodigio]

I have a 300 watt inverter with a cigarette plug that I used to watch tv on my last trailer, a toy hauler. However, on my new fifth wheel there is no outlet.

There is a dual usb charging port right by the tv, so I am thinking about replacing this with a combination usb and cigarette style outlet.

The tv is towards the rear of the trailer, so the existing wire run is probably 30 ft. or so. I have read that the inverter should be placed as near to the batteries as possible.

So before I purchase the 12 volt outlet and dig into the wiring, does what I am trying to do going to work?

[Iwritecode]

You could just use an adapter.

https://www.amazon.com/Cigarette-Lig.../dp/B07N1LZ693

[rodigio]

Thanks. I actually looked at this adapter, but it says the output is 8W max, and I don't think that will power my tv (75 watts).

[Chuck_S]

Take a look at the power "brick" for your TV (if it has one). Many of these power supplies just convert wall 120vAC current to something in the 12-15vDC range for the TV. Easy enough to just power your TV directly from 12vDC rather than invert DC to AC and then then convert it back.

-- Chuck

[CedarCreekWoody]

If you install a 12 volt cigarette plug to power an inverter be sure to use heavy guage wire rated for the inverter amperage draw AND distance from power source. Wiring feeding a USB port is most likely too light as these are low amperage appliances.

[KyDan]

Originally Posted by CedarCreekWoody

If you install a 12 volt cigarette plug to power an inverter be sure to use heavy guage wire rated for the inverter amperage draw AND distance from power source. Wiring feeding a USB port is most likely too light as these are low amperage appliances.

What he said!!

[KyDan]

Originally Posted by Chuck_S

Take a look at the power "brick" for your TV (if it has one). Many of these power supplies just convert wall 120vAC current to something in the 12-15vDC range for the TV. Easy enough to just power your TV directly from 12vDC rather than invert DC to AC and then then convert it back.
-- Chuck

Hi Chuck, I have seen this eliminate the puck suggestion many times here on FRF but I believe it's probably the exception rather than the rule.
At least in my experience it's not possible for my stuff.
Example the LG monitor I'm using at this moment has a 19VDC puck/power supply. The Panasonic in my bedroom and the LG big screen in my family room and the Jensen in my trailer all use power supplies in the 19-24 volt range. (I really wanted that Jensen to be 12v!)
It's definitely worth checking out but usually won't work

[Chuck_S]

(Just back from crawling under my desk.. )

The Samsung TV I use for a monitor uses 19vDC as well -- never hurts to check as a smaller one only needs 14vDC (2.14 amps) which is probably close enough . I didn't bother to check the 50-odd inch plasma TV that heats my office.

I'm curious if a pure-sine wave inverter may be necessary as these are (or used to be) much more expensive than simple inverters but the combination seemed to work.

Rather than trying to MacGyver an existing 120vAC TV and small inverter into the trailer there are televisions advertised as "12v RV" types which won't take an electrical engineering degree and contractors to install.

-- Chuck

[rodigio]

Originally Posted by CedarCreekWoody

If you install a 12 volt cigarette plug to power an inverter be sure to use heavy guage wire rated for the inverter amperage draw AND distance from power source. Wiring feeding a USB port is most likely too light as these are low amperage appliances.

If I was running new wire, I would use heavy gauge wire, plus I would locate the inverter near the batteries.

However, my plan is to use the existing wire that feeds the usb charging outlet, which is approximately 30 ft from batteries.

What gauge wire would the existing wire need to be to run my 300 watt inverter safely? And yes, it is a pure sine wave inverter.

[nvs4602]

Originally Posted by Chuck_S

(Just back from crawling under my desk.. )

The Samsung TV I use for a monitor uses 19vDC as well -- never hurts to check as a smaller one only needs 14vDC (2.14 amps) which is probably close enough . I didn't bother to check the 50-odd inch plasma TV that heats my office.

I'm curious if a pure-sine wave inverter may be necessary as these are (or used to be) much more expensive than simple inverters but the combination seemed to work.

Rather than trying to MacGyver an existing 120vAC TV and small inverter into the trailer there are televisions advertised as "12v RV" types which won't take an electrical engineering degree and contractors to install.

-- Chuck

I made my own 12v to ??v it's adjustable so I can change it if I need to. Just buy a 12vdc boost converter.

https://smile.amazon.com/dp/B08246FB...89DETGR6HZ0749

I bought the plastic box for it at Walmart in the hobby section. Here's a link to the one I got so you know what to look for.

https://www.thebeadery.com/shop/2184...04724121093750

The cigarette lighter plug has a 10a fuse built in.

[KyDan]

Originally Posted by rodigio

If I was running new wire, I would use heavy gauge wire, plus I would locate the inverter near the batteries.

However, my plan is to use the existing wire that feeds the usb charging outlet, which is approximately 30 ft from batteries.

What gauge wire would the existing wire need to be to run my 300 watt inverter safely? And yes, it is a pure sine wave inverter.

A 300 watt inverter could draw 25 amps so you need 10 GA wire.

[rk06382]

Originally Posted by rodigio

If I was running new wire, I would use heavy gauge wire, plus I would locate the inverter near the batteries.

However, my plan is to use the existing wire that feeds the usb charging outlet, which is approximately 30 ft from batteries.

What gauge wire would the existing wire need to be to run my 300 watt inverter safely? And yes, it is a pure sine wave inverter.

A 300 watt inverter will be almost 30 amps @ 12v. You will need a least a 10 AWG wire.


Edit: Sorry for the duplication. I did not see KyDan's reply until after I posted.

[Bob K4TAX]

Folks dealing with electricity need to learn and understand a wee bit about OHMS Law. Where as:

E = volts, I = amps, R = resistance, P = watts

Therefore:
I = E / R
R = E / I
E = I x R
P = E x I

And with a bit of algebra, remember that class that you said you'd never use? Well, one can resolve the equations for other values.

Thus 300 watts = E 12volts x I 25amps
or I = P / E 300watts / 12volts = 25amps

[NavyLCDR]

Don't forget, an inverter will only draw as much power as required for what is plugged into it. My TV is about 5 ft directly above my converter and there was existing wiring to the DVD/Stereo directly above the TV. There was also a convenient hole already there where the HDMI cable dropped down. So I poked two wires from a cheap Harbor Freight 300 watt inverter up through the same hole for the HDMI cable and tied into the power supply wires for the DVD/Stereo. I need less than 100 watts total for TV, Raspberry Pi media player, and Roku box.

No problems here, I did not change the 15 amp DC fuse feeding it and it has not blown yet. If I was going to do anything heavier, I would replace the wiring down to the power center and increase the DC fuse amp rating, but I have not needed to. In summary - don't change the fuse rating if you are going to use the existing wiring. If the fuse blows, you need heavier gauge wire to move up in fuse rating.

[rk06382]

Originally Posted by Bob K4TAX

Folks dealing with electricity need to learn and understand a wee bit about OHMS Law. Where as:

E = volts, I = amps, R = resistance, P = watts

Therefore:
I = E / R
R = E / I
E = I x R
P = E x I

And with a bit of algebra, remember that class that you said you'd never use? Well, one can resolve the equations for other values.

Thus 300 watts = E 12volts x I 25amps
or I = P / E 300watts / 12volts = 25amps

How much power is lost to produce 300 watts.


Allow for inverter efficiency, typically 85%, divide the figure by 0.85. Thus:


For a 300W load at 12V....300 ÷ 12 ÷ 0.85 = 29.4 Amps.

[darrellr]

Originally Posted by NavyLCDR

Don't forget, an inverter will only draw as much power as required for what is plugged into it.

Technically incorrect. This would only be true if the inverter were 100% efficient. Given they are closer to 80-90% efficient, they will draw what it is connected to it plus the amount of power the inverter uses to invert the DC to AC.

[NavyLCDR]

Originally Posted by darrellr

Technically incorrect. This would only be true if the inverter were 100% efficient. Given they are closer to 80-90% efficient, they will draw what it is connected to it plus the amount of power the inverter uses to invert the DC to AC.

OK, you got me!

[Aspendog]

10 AWG wire and this:



https://12vtechnology.com/products/w...-lighter-style


12v 25 amp receptacle. Installed 2 on our RV. One for CPAP and the other for a 300 inverter so wife could plug in curling iron.


Automotive cigarette lighters are only 5 amp.

[wabakami]

Due to losses in the wire length use 8ga wire for safety.

Just because you only need 100w for the TV, you think, "hmm, I can use 14ga wire to save money or rewiring my rig", etc. What happens when someone plugs in multiple items, now you're drawing, maybe 18a or 23a, through a wire that can barely handle 15a?

Maybe you'll be able to claim the fire insurance after the insulation melts off the 14ga wire and destroys your dreams!

I'm a master electrician and amateurs dealing with electrical issues, whether 12V or 240V, they scare the hell out of me.

Just my 3 cents Canadian.
Geoff
.

[Midwest Ed]

Originally Posted by wabakami

Just because you only need 100w for the TV, you think, "hmm, I can use 14ga wire to save money or rewiring my rig", etc. What happens when someone plugs in multiple items, now you're drawing, maybe 18a or 23a, through a wire that can barely handle 15a?

One could always add an inline fuse holder and fuse properly rated for the existing wire gauge or whatever is the "weakest link" (i.e. wire gauge or inverter rating).