sixwheeledbeast

Hi all,
I have just aquired myself a 7 inch LCD monitor from a local car boot.
I thought this would make a useful test monitor as I am a CCTV engineer.
It has come with a dc plug with 500mm length of wire cut off
The unit is a tevion TWS704. 9 Volt dc.

My idea is to have some sort of battery pack that I can plug it into my van to charge while i am driving. Then when I arrive on sited I can use the unit "wirefree" up my ladder.

I can get hold of a large varity of 12vdc sealed lead acid batteries can this be charged via my van and use a simple 9 volt zener circuit.
Is this the best method, any help/idea greatly appreciated. Thanks

Shax

I'd use a standard 3 pin 78x08 8 volt regulator, with 2 silicon diodes in series on the common terminal..
Should give you about 9.2v......

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Shax.
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justDIY

hows about using a LDO regulator, such as the LM1084 ... It has 1.5v of dropout at 5a and considerably less at lower current levels

It will make your gel cell last longer.

If you can measure how much current your lcd needs, another solution would be a boost converter. Something like the Anyvolt uses a buck-boost topology making it ideal for batteries ... start with a 4 pack of AA's or C's or whatever you can get ahold of cheap, and the anyvolt will suck them dry for you.

http://www.dimensionengineering.com/AnyVoltMicro.htm

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sixwheeledbeast

Is it possible to charge a 12volt 3.2Ah lead acid battery from a car cigarette lighter. What sort of circuit would I need.

I was planing to use a 12 volt battery and this circuit
http://www.uoguelph.ca/~antoon/circ/car912.htm
The transistor is like for like (BD441 or 2N5192).

I just need to keep the battery charged in my van.

Thanks for all suggestions.

Hero999

How much current does it draw?

I'd recommend a switching regulator if it's >1A as it'll save a lot of battery life.

Another thing is, there's a chance it already has a built-in switching power supply and will run straight from 12V with no problems.

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justDIY

if you wanted to be safe, you could charge the battery through a light bulb, to limit the inrush current.

check the specs on your battery for a fast charge voltage, and then check the voltage your van's alternator pumps out with the engine running.

just connecting one 12v battery to another isn't going to get much charging done - most likely it will just trickle charge the little one from the big one, unless the big one is old or has a low voltage for some reason. actually, a schottky diode wouldn't be a bad idea, to keep the little one from draining back into the system.

__________________
If you don't have a planet, what good are gold bars?

want to contact me directly? gmail gordonthree
check out my project website: http://projects.dimension-x.net
Favorite numbers:
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

sixwheeledbeast

I was thinking maybe a diode of some description.
The monitor runs straight off my 12 Volt battery so I can use it which is good.
My battery specs are:-

BS123N
12VDC - 13.8VDC MAX.
3.2AH @ 20 H Rate
0.96A Max Charging Current
16A Max Discharge Current

Van alternator is 75A
Battery is 62A with a regulated 13.8 Volt cigarette output.

Hero999

That's a good idea but I'd use a bulb rated to a much lower voltage than 12V, a 3V torch bulb should do the trick.

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