Can I power a TV directly from 12V lighter socket?

Discussion in 'The Projects Forum' started by BoatMan, Aug 22, 2012.

1. BoatMan Thread Starter New Member

Aug 22, 2012
3
0
Greetings!

I want to quickly say that this is by far the most intelligent group of people I have ever encountered on the net! The level of knowledge here is incredible.

My question is going to seem very ignorant in light of the sophisticated minds on this board, so I beg for your mercy in advance!

I want to use a TV on my boat utilizing the lighter socket since there is not household power available. After much searching, I found a 19" flatscreen that uses a plug-in 120VAC transformer that steps the voltage down to 12VDC at 3A (printed on the pack and the input side of TV) It is detachable, not hardwired into the TV.

I went to Radio Shack and looked at a 12V power adapter that provides different tips, and has a switch to adjust output voltage and respective amperage.

See here

Well, the highest amperage at 12V is 2.5A

What are my options, if any, to increase that value so the TV will function properly? I can't raise the voltage of my boats battery, so I must decrease resistance in the circuit. How do I do that on what is probably a PCB in that power adapter?

Can I make a cable that terminates with the appropriate fitting for the TV input and a 12V lighter socket plug? Wouldn't the lack of current regulation fry the TV in an instant? My lighter socket has a 20A fuse. I know I could change it to a smaller one; but unless I am mistaken, a fuse does not regulate current, only prevents over-current, correct? Am I over-thinking this?

How do I build a resistive circuit to get my 12V lighter socket to deliver 3A safely? Or, maybe you good people can direct me to a website that sells a ready-made power adapter in that configuration. Radio Shack has a bunch of different versions online, but none are 12V/3A specific. Either too high/too low or wrong tip.

Examples:

My dilemma is...I don't understand if the TV's circuitry REQUIRES a closely regulated power supply, or if it can withstand minor amperage swings. If anyone wants to give me an education on this topic...I would be so grateful!

Thank you again in advance for entertaining my ridiculously long question to which I know exists a simple answer!

2. debe AAC Fanatic!

Sep 21, 2010
1,101
239
The TV will only draw what it wants as current. The voltage is what needs to be right. Most 12V TVs will work fine of the 12V system on your boat. I used to run one on my boat as a video monitor for an underwater camera.

3. wayneh Expert

Sep 9, 2010
14,850
5,333
You have two issues; the "mechanical" and the electrical.

As for the electrical, I agree that the TV will likely be just fine plugged directly into your boat's system. Do you plan to use the TV while running the engine? A car or boat electrical system can be quite noisy - especially while active - with voltage spikes and dips. So there is some small risk that these will not be tolerated by your TV. Personally, and if the TV is not terribly expensive, I'd be tempted to just try it and hope for the best. Very likely to be fine.

The mechanical connection is a good DIY project. You do not need all those fancy voltage switches and options. An LED indicator is always nice but not critical. Are you sure you want to use the cigarette lighter? You already know the connectors you need on both ends. The only other thing I'd want in line besides the wire itself, is a fuse. Something like 2.5A or 3A. Many adapters have a fuse built right into them. Depending on what you can find, you could just use an old lamp cord and put the connectors on either end of it.

4. BoatMan Thread Starter New Member

Aug 22, 2012
3
0
Thank you both for your replies!

So it really is that simple...I don't need to worry about the amps available at the lighter socket? I was always under the impression that too much available current would fry sensitive electronic equipment.

I was also concerned about the issue of engine running voltages, as the battery's static voltage is 12.7, but jumps to 14.7 from the alternator charging circuit when engine is running. I won't be using the TV while the engine is running, and I am going to use a dedicated deep cycle battery to power the TV, fans, radio etc. with a switch to isolate it from the engine starting circuit. I will fabricate my own cord with a 3A fused adapter and give it a try.

The reason I was going to use the lighter socket is because it was the only point of entry into the electrical system that didn't require dissembling the dash or pulling out the stereo system to tap into its wiring.

I do have a related follow-up question. I have a friend who uses a power inverter that provides the 120VAC receptacle for his "regular" TV. I researched this option, but immediately realized what I thought was a disadvantage...

Is it true that a "power inverter" that steps 12VDC up to 120VAC, only to be converted back to 12VDC is in fact, far less electrically efficient than simply going DC to DC as in my case? This is why I bought the TV, because I could skip the power inverter in the electrical chain. My friend thinks I spent more money on the TV than what it was worth to avoid the inverter.

Who is right?

BTW, his is an old 13" tube style TV that must be plugged into a wall socket. I paid \$180 for mine, and could have gotten a non-12V version for \$50 less. But the inverter would have been \$50! Did I do good?

Thanks again for the replies!

5. R!f@@ AAC Fanatic!

Apr 2, 2009
9,664
1,110
What u did is what any one else would have done in AAC.

Most of the LCD's need just 12VDC to work.
I am here if you decide to take it apart to give DC directly. it's really nothing to it.

6. wayneh Expert

Sep 9, 2010
14,850
5,333
Right, no worries. Think of voltage as water pressure. If the device you are supplying can stand the "pressure", it will operate however it's supposed to, taking as much water or current as it needs. No matter how much water might be available, a garden hose will deliver the same amount when supplied the same pressure.

Comparing to your friend's system requires setting the goals. Maybe he can beat you when considering dollars only, maybe not. But your system might be more efficient and uses less components, and hence be more elegant. That's hard to measure but has real value. It's worth noting that his CRT may not run off of 12V even if you could get at the innards.

If you really want to win the argument, start talking about picture quality and run-time on a given battery. I think you'll win big time!

7. DerStrom8 Well-Known Member

Feb 20, 2011
2,424
1,355
If you choose to use your cigarette lighter adapter, make sure you keep an eye on its temperature. You said it can source 2.5A. If your TV tries drawing 3A from it, it might start to get a little hot. I'm sure the tolerance will be able to handle the extra 500mA, but it would be good to keep an eye on it anyway, just in case.

8. BoatMan Thread Starter New Member

Aug 22, 2012
3
0
Thank you everyone for clearing up my confusion! I am going to assemble a cord this morning and try it.

Cheers!

9. bumba000 Member

Oct 7, 2015
89
4
yeah, I realize the age of this thread, but I just came across it and just had to interject. Do you realize that there are many TV's that are made to be powered using a lighter socket car cord?? http://www.12volt-travel.com/12-volt-televisions-c-684.html

They really don't use much power and you don't have to hunt for a cord that may work or may catch fire.

10. wayneh Expert

Sep 9, 2010
14,850
5,333
The thread starter hasn't been around for 4 years. I doubt he's still waiting for advice.

11. #12 Expert

Nov 30, 2010
18,078
9,619
Right this very minute, my computer is plugged in to an electrical grid that can provide at least 100,000 amps. I works just fine because the voltage is correct.

wayneh likes this.
12. bumba000 Member

Oct 7, 2015
89
4
I didn't figure he was. Point is, I came across the thread I'm sure others will too and they might find what I had to say useful. Thanks though...