Portable battery and inverter

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  #1  
Old 07-04-10, 05:47 AM
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Portable battery and inverter

Hi there,

Iím trying to set up a portable security system to monitor some consistent vandalism on bicycle, but am having some problems.

The main problem is that the inverter I got doesnít draw power from my portable battery. (It works fine from the carís cigarette lighter.) I tried to Google this, but canít find the right info on using inverters with portable batteries. Any suggestions? (Specs are below.)

Secondly, Iím just wondering if this system seems alright. I need about 9-10 hours of monitoring/day. The battery says it provides about 14 hours at a 4w draw. I guess I lose some of that with the inverter and then I guess itís good not to let the battery run down too far. Does that seem alright?

If you need more info, please ask or check out the links below. (Oh, and since I'm in Japan, these are Japanese products so the links will bring you to a Google translation of the Japanese page. Makes it all the more difficult for me to figure things out. )

Thanks!


Battery
DC12V ē 7.0Ah
Output voltage: DC12V
Cigarette lighter type socket ● (84W or less) with a cigarette lighter

CD 150 Power Inverter
Input voltage: DC12V
Output voltage: AC100V
Rated output: 130W
Maximum continuous (30 min) output: 150W
Maximum instantaneous output: 200W
Output frequency: 55Hz (square wave)

Camera
Power Source DC12V,0.5A (AC adapter)
Power Consumption 3.84W
 
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Old 07-04-10, 06:05 AM
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Is the small battery charged? Why do you need 120 volts?
 
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Old 07-04-10, 09:37 AM
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If that camera is the only thing hooked up to the battery (no recorder or anything), then you don't need the inverter at all. The camera's AC adapter is outputting 12v. So you can ditch the adapter completely and just wire the barrel plug right to the battery. Just be sure you have the polarity correct. Normally the center pin will be positive. There will be a little picture similar to this: - -(ē- + ... That means positive center. If it's negative center, the + and - will be reversed on the picture.
 
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Old 07-07-10, 08:42 AM
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@JerseyMatt I see what you mean; that's a big help. The diagram on the AC adapter shows the center pin to be positive as your diagram shows. But I must be missing something still: how do I know which wire in the cord is positive (connected to the center pin)? There are 1cm gray bars running down one side of the cord. Do you know if this indicates positive or negative? Thanks.

@telecom guy Sorry, I'm not entirely sure what you mean, unless you are referring to the what JerseyMatt pointed out: I only really need 12V instead of 120V (actually 100V here in Japan).

Thanks for the replies!

By the way, I'd like to use this battery for other applications once I'm finished with this one, and I don't fancy chopping up all my other cords. Plus I'm curious. So do you know what reason the inverter didn't work with the battery? Does the inverter have a component that triggers it when hooked up to a running car? Or...
 
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Old 07-07-10, 10:27 AM
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Unfortunately it could be either, depending on the manufacturer. In my experience it's USUALLY negative. You can get a cheap continuity tester or multimeter and verify it for yourself. Or, you can get something like this, so you don't have to cut up your adapter..

http://www.mcmelectronics.com/produc...-5361-/24-5361



This is the most common size for 12v cameras (5.5mm barrel with a 2.1mm hole for the pin).

As for why the inverter isn't working, I'm not exactly sure. There is no such circuitry to detect a running car in an inverter, but there is a low voltage cutoff. That usually kicks in at 11-11.5 volts to keep the battery from draining too low. If the battery isn't fully charged, the inverter may just refuse to turn on.
 
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