Gafferbill said:
........don't bother with a 12 volt TV.
Buy the mains TV of a reasonable size that you like and run it from a 12 volt inverter which you can buy for around £25 for a 150 Watt model...........modified sign wave inverters are fine for this job.
Some TVs are manufactured in bulk to run off 12 volts DC and are supplied with a mains power source to supply this voltage that is specific to the country of sale.
These TVs require a stabilised 12 volts........not 11.5 to 14.2 volts that may be the case in a caravan.
it is better to run this type of TV via an inverter through the power source to get a stabilised 12 volt supply.
Specific 12 volt caravan TVs are expensive as they are manufactured specifically to cope with fluctuating voltage.
I'm sorry but I can't agree with the recommendation of using a 12Vdc to 230Vac modified sine wave inverter.
I have tried to use a laptop on a modified sinewave inverter, and it failed miserably. Fortunately no apparent damage was done, but I have no way of knowing if the power waveform may have weakened any components which may lead to premature failure in the future.
Modified sine wave inverters are the most efficient converters, but they produce some rather nasty quality mains voltages. They are not the nice smooth constantly changing voltage of a sine wave, but they step between set voltages to poorly mimic a sine wave. They are fine working into purely resistive loads, such as incandescent lamps and heaters, but as soon as any device with reactance or inductance is connected, (eg motors, and many modern electronic items that use switch mode power supplies (SMPS), The output voltages and currents often produce quite nasty artifacts that can can prevent equipment from working and may actually damage connected equipment.
Symptoms include the equipment generating more heat than is usual,
Laptops and TV's not working or visual disturbances on the screen.
sometimes audible squealing and uneven running from motors and running slower than expected.
If you get any of these symptoms you must stop using the inverter immediately.
If you must go for an inverter make sure its is a Pure Sine wave model. These produce a full sine wave and avoid the nasty step changes and transient oscillations of the modified sine wave inverters. Unfortunately, they are more expensive, and less efficient, but a far safer option if you are using expensive appliances.
I do agree with gaffer that many of the smaller TV that actually need 12V from a an inline power supply do require a high quality of DC power, and my may not work properly if just connected to the caravan's 12V supply, but to use an inverter then to reconvert it back to 12V is not especially efficient.
As an alternative solution, there are what are called buck converters. These only cost a few pounds, and the type that do both up and down conversions often can be preset to produce a pretty stable 12V dc output even with inputs as low as 5Vdc. The trade off is the current draw of the converter rises as the input voltage falls to maintain a constant power conversion. These have become more popular as they allow the variable outputs from renewable energy generators (wind, and solar) to provide the optimum charge for storage batteries.