# Power Inverter



## Kilree (Apr 28, 2011)

Hi, I intend using an inverter for TV and Sat when an EHU is not available. The TV is a 19" LCD Flat screen Mains operated drawing 45W when running. The sat receiver is both 12V and AC240 which obviously would be run on 12V connection in the TV compartment.
My query is this: If I run the TV through a 150W or 300W (Max) inverter will there be any problems attaching it to the 12V cigarette socket contained in the TV cabinet of the M/H. I have seen it mentioned on some inverter instructions that they should be connected directly to the vehicle battery and I presume this is through the cig lighter socket on the dashboard. Any help and advice would be much appreciated


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## pieterv (Feb 3, 2009)

It all depends on how much current the 12V socket is rated at. The one in my TV cupboard says 10A, which equals 120W.

using a 300W inverter doesn't mean it always uses 300W, it depends on what you connect to it. As a rule of thumb add all the wattages of the connected equipment and divide by 0.9 (because the inverter will be about 90% efficient, so you use a bit more). This is the power you will use, dividing that by 12, gives you the current. That should stay below the max of the outlet.

Hope this helps,

Pieter


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## napoleon (Apr 30, 2011)

Hi Kilree, 
Can only speak from experience and not from technical `know how` but I have been using my 12V cigarette socket in the TV cabinet for running my TV through a 300W inverter for the last 2 years with no problems so far. the only `downside` is that it can be a little noisy.
napoleon 8)


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## Touchwood_RV (May 1, 2005)

*Inverter*

Hi Kilree, is there not a simple 12 volt option for your TV?

As Pietrev says it depends on the power socket rated amperage - don't exceed it as that can be a cause of fire especially if the protection fuse has been wrongly upgraded in the past. 
Yes the 0.9 or even 0.8 rule of thumb is a good one allows for efficiency overheads in the design.

If you plan to use this option regularly I would suggest have your dealer or local sparks install the inverter hard wired with appropriate fused protection to the source and kept as close to the source as possible to minimise 12volt cable runs, also depending on where this is will reduce the audible inverter noise, then from the inverter run a 2.5mm 240v mains flex to the TV cupboard install a new 13amp socket, when power required from the inverter just move the plug from the standard mains socket to the new inverter socket, switch on the inverter and away you go. NB never for safety reasons put the inverter in the same cupboard/locker as the source.


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## Kilree (Apr 28, 2011)

This really is a very friendly forum and thank you Pieter, napoleon and Steve for your replys. I'll check the rating on the 12V socket to see what it says. The only item I can see myself using from the inverter would be the Toshiba TV which has no 12V running option. It is strictly a mains TV and the rating on the label on the back reads 45W.
Steve your suggesting for hardwiring the inverter might be a runner as we will not always have access to EHU. This is our first venture into Motorhoming having been caravanners for many years and we would intend (where it is suitable) to do some "wild camping".
Jusat one query - will all inverters be noisy as napoleon describes or is that something that happens with higher powered ones say from 300 up. For my requirements I think that even a 150w would do.
Many thanks again for all the advice.
John.


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## solentviews (May 9, 2005)

napoleon, I originally had a 300w inverter with the fan noise but I changed to a 150w and everything performs the same with no noise, there is no fan in my 150w inverter!
Hope this helps
Ian


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## Kilree (Apr 28, 2011)

Hi guys, I've checked the cig lighter socket in the TV cabinets and it says max 4 amps which seems to me to be very low in view of the one in Pieters M/H. Using the formula I don't even think that it will allow me to connect even a 150 W inverter or am I miscalculating.?
John.


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## Mrplodd (Mar 4, 2008)

I have hard wired my inverter to the leisure battery and run a 240V cable to the TV cabinet and installed a dedicated inverter fed socket, simples!!!

Its VITAL to keep the cable run from leisure battery to inverter as short as is possible (and to make sure the cable is thick enough to minimise voltage drop.)


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## Touchwood_RV (May 1, 2005)

*Inverter near source*

Hi John,
Noise is subjective and relates to the size power draw and the quality. Good quality low power units should be silent, the bigger you get then the more heat it needs to dissipate, so fans come into play, also if they are on the cheaper side then can be noisy by design unfortunately.

If you are considering built in then give this design some consideration, I have a 3KVA inverter with a large battery bank in my MH. It has a pass through facility, that is the power to one of the ring mains in the MH is live via the EHU but when off EHU the inverter is switched on and it powers all of that ring main, i.e. microwave, TV, Freeview decoder, and anything else we need to plug such a kettle…. Clearly you may not need 3KVA, but the design theory is a good move provides bags of flexibility for wild camping. Large battery bank, solar panels and you have it made for wild camping.

The nearer to the power source the inverter is the better all round, keep your 12 volt cables as short as possible.

Just one thing to remember power consumption, I = P ÷ E (AMPS = Watts / Voltage) Example: 1,000 WATTS + efficiency factor rule of thumb 0.85 (1000/0.85) = 1176w divided by 12v = 98 AMPS [efficiency factor - never buy an inverter rated at the watts you need, as all inverters have an efficiency factor of between 0.85 and 0.9, in other words due to internal overheads they lose that amount capacity, get one slightly larger than required]

EDIT: Posted this then spotted Mrplodd's post - seems we recommending very much the same thing.


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## Jezport (Jun 19, 2008)

The best way is to connect the inverter as close to the battery as possible.

I have seen a lot of tv interference caused by modified sinewave inverters so would advise that you get a pure sinewave inverter if funds will stretch to one.


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## Kilree (Apr 28, 2011)

Thanks for the help everyone. At the end of the day I think I will opt for the hard wired solution but in the meantime I purchased a 150W inverter today and it operates the mains TV perfectly. I am happy enough with this for the moment but will probably go with a more permanent solution when things are a bit quieter.
Thanks again.


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## DJP (May 9, 2005)

I would put the inverter as close to the battery as well, then run a mains extension lead up to the TV or hard fix a socket (240v from inverter) by the TV.


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## teensvan (May 9, 2005)

Hi.

We started off with a 300 watt inverter running our TV which used 50 watt. The trouble is that all TVs need a start up current draw which for less than 1 second can exceed 300 watt. This all works well as long as you have a fully charged set of batteries, but if they are at around half charged state the inverter may stop running and not power up your TV as we found. 

This only what happened to us and now we run a 1000 watt inverter which seems to cope with the inrush current better.

It is also best to fit the inverter as near to the batteries as possible to reduce volt drop on the 12 volt side, and have longer runs of 240 volt cables.

steve & ann. ------- teensvan


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