I have this awesome light that plugs into the wall and has a 9v dc output.  I want to snip that plug off and mate it to a cigarette lighter plug and use in on the kayak. Here are a few pictures (lights are blue LED and chap stick is for size reference) I am also posting a link to the battery I plan to use. 

https://nocqua.com/product/pro-power-kit/

What makes you think cutting an AC plug off a 9v adapter, adding a cig lighter, and powering it by 12v will work?  Why not find 12v lights?

8 minutes ago, J Francho said:

What makes you think cutting an AC plug off a 9v adapter, adding a cig lighter, and powering it by 12v will work?  Why not find 12v lights?

Plugging a 9v light system, especially LEDs, into a 12v outlet is asking for one thing - blown LEDs. There's a reason those power supplies are matched, over-voltage on LEDs will make them brighter...until they overload and go dark forever.

19 minutes ago, J Francho said:

What makes you think cutting an AC plug off a 9v adapter, adding a cig lighter, and powering it by 12v will work?  Why not find 12v lights?

Because I like free and these were something I found in the junk drawer the other day. If it won't work it just wont work. That's the reason for asking the question and not just going ahead and doing it.........I was always told there is no such thing as a dumb question........dumb answers are a dime a dozen though.  

There are dozens of options for 12v LED lights under $20.

The answer is no. DC current requires a ground wire; 1 power wire & 1 ground wire, it's called  direct current. AC doesn't require a ground wire, 1 power wire, 1 common wire, it's called alternating current, the ground wire is a optional 3rd wire for safety.

Tom

 

You can..... but you will need an understanding of dc circuits, power, volts, amps, resistance, etc.  This is not a cut and tape and hope it works type of job.  You would need to build a circuit where only 9v of the possible 12v supplied by the battery is going to the led light.  I have built many voltage reducing devices to run lower voltage items off of available batteries.  Most of the time it is not cheap to source the proper components (regulator, resistors, enclosure) for something that will be exposed to the elements.  I do it more as a way to keep myself busy with small projects in the winter before the lakes thaw out.  It can be done, but as J Francho stated, there are lots of inexpensive options.

Here's another $8 option

 

https://www.amazon.com/Magnolian-Efficiency-Converter-Supply-Waterproof/dp/B00A71E52G/ref=sr_1_3?ie=UTF8&qid=1548274742&sr=8-3&keywords=12v+to+9v+dc+converter

Thanks for the advice fellas. I know of a few other options I've been looking at. I'll go that route. I just figured I'd check and see before I spent any money. I dont need anything fancy. Just a small rarely used light source for when I'm sitting there waiting on the sun to start coming up. 

You can always just use a 9v battery clip and a 9V battery. I like duracell but energizer work too. Not sure how long it will last but it will work if you get the polarity right.

I made a 12v LED light pod.  Very I expensive.  You can customize it how you like.  Just get the lights and the wire in the link.  Great for working and fishing at night.

 

http://jaimeastin.com/2018/11/03/create-a-portable-work-light/