The Samsung and other small TVs that use an external brick are not advertised as being 12V capable. None of the literature makes note of it and e-mails and phone calls will not yield anything other than to use it with the brick plugged in to the wall.
However, MANY MANY of us have done EXACTLY what you are proposing with no problems. Many of the smaller Vizios and Insignia TVs use a external brick and the TV has a 12VDC input. A trip to radioshack can get you a 12V power port cable and the a choice of the correct tip for the TV allowing you to power the TV straight from the 12V power port.
The home TVs with the external power brick cost less and are usually better built than the pricy "12V" models. Some people are concerned the TV may not have a voltage regulator built in and not be able to handle the variable voltage put out by the 3 stage chargers. I have yet to here anyone on here with one fail because of this. I have had my Insignia 22" LED for 5 years now powered from the 12V power port exclusivly.
One thing you may double check with the Samsung. If it is 14VDC and not 12VDC input, it may not work. Fully charged batteries are 12.7V and gradually discharge to around 11.8V at 60% discharged. I know my Insignia can tollerate about 10% low voltage before it shuts off. If the Samsung is similar and is 14V, it may not even opperate below 12.5V, which is still a good state of charge for batteries. You would need to look for something like a Vizio that is 12VDC input.
Good Luck!