There are a Myriad of options to power these devices safely and still be able to start the engine.
Here is the simplest. Acquire a Basic bell and whistle free jumper pack, and try your best to always keep it fully charged.
Use your devices as you wish, and if the engine fails to start, use the jumper pack to assist the engine battery to start the engine. After a jump start is needed, much driving, not idling, is required to recharge the battery. At least 2 hours to get back to 80% charged, and another 4 to 6 hours to get in the 95% range, and that last 5% might never happen by the alternator, no matter how much driving you do.
As this much driving is unlikely to occur, the Starting battery will never reach full charge, and it will degrade very quickly, but especially if left under 80% charged.
When it does fail, and it will, Replacing it with a Marine battery( the biggest which will fit) is wise as a marine battery is better able to handle deeper cycles than a starting battery, but nowhere near as well as a true deep cycle battery, which in 12v form, are actually hard to acquire and much more expensive
The starting battery will quickly degrade when cycled deeply.
After using the jumper pack, it needs to be recharged too, as it will degrade faster if left in a partial state of charge. But you can likely get 2 to 4 engine assists from it before it cannot assist in jump starting. These jumper packs come with chargers that will require at least 24 hours to bring the jumper pack back upto full. One can recharge these while driving too but I will not go into that here.
Jumper packs are not strong enough on their own to crank most engines. They are assisting the depleted engine battery. if the engine battery is too depleted, it cannot do it. Try to get one which has the 18 A/h battery inside. Many will have a 12 A/h battery or even smaller. Do not get one with an inverter or air compressor in it. These add on devices are very low ball quality and will fail to perform adequately, or just outright fail. If you find one on sale, it might have been sitting on the shelf so long that the internal battery has already lost a good portion of its original capacity. Freshness, with batteries, counts.
While Voltage is not a great indicator of state of charge, as so many seem to think, it is still a cheap tool to get a ball park idea. If you drain the engine battery into the low 11volt range with the TV, you are approaching the point where the Jumper pack might not be able to assist the engine battery to crank the engine. Many variables affect this minimum safe voltage for assisted engine start.
A product like this can work well for a Newbie:
http://www.amazon.com/INNOVA-3721-B...UTF8&qid=1406831974&sr=1-7&keywords=voltmeter
Plug it in, and when you see less than ~11.5 volts, see how well your engine cranks( if at all) without assist from the jumper pack. It will be different for each vehicle.
It is better to have a real voltmeter and take voltage readings right on the battery terminals. Harbor freight has an inexpensive, sometimes free, voltmeter which is accurate enough and better than the linked product above, though less convenient.
http://www.harborfreight.com/7-function-multimeter-98025.html
The ultimate solution is a full size additional Deep cycle battery with all loads wired to it, but judging by your question, this is well beyond your knowledge to set up. If you will be doing this( living from/in a Van) for a while it can be in your best interest to do it now, rather than do the jumper pack thing.
There are many threads containing info about the many methods of setting up a secondary battery to charge with the engine running and have it separate with engine not running. Please do some searching.
Also keep in mind, these older tube tv's can draw 3 to 5 times as much power as a new LED backlit flat screen tv.
Older TV's will not be able to pick up both ATSC( digital) broadcast signals and the former NTSC analog signals. A separate converter box will be required adding to the demands on the battery.
Old CRT tv's can more trouble than they are worth
thanks guys and gals. Much love.
