# LED Flashlight run from 12V SLA battery. Do-able?



## p67 (Aug 25, 2012)

Along with some other projects I was thinking....

Can you take out the battery section of an LED flashlight and run it off a 12V battery. PROVIDED you regulate the DC power supply from 12V to whatever the flashlight was originally intended for?

Why? Cause those special batteries are expensive as and last maybe an hour on full. I want to be able to spotlight all night.

So my plan is to buy a half decent flashlight with a decent LED and reflector. Remove the battery pack, so essentially I have a hollow tube and fit a DC-DC regulator to a normal 12V 7AH SLA battery and in theory, have 5hours run time.

You can buy some pretty simple DC-DC regulator circuit boards on eBay rated to 2A-3A max for next to nothing. Adjustable outputs too. Something like a switching step-down regulator here may work?
http://www.ebay.com/itm/AX3022-Base...ltDomain_0&hash=item19d4245cff#ht_3677wt_1159

Has anyone done this?

Can anyone see any problems with this?

Appreciate some input.


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## khergert (Aug 25, 2012)

Sure, it's an idea. 10 or more years ago Willie Hunt was with Surefire and sold pwm voltage regulators. I had or have a 24v to 14.4. the only downside of SLA batteries is weight. I ran over volted 10w halogens. That must be out of style now. I'm not sure what I would use today. For simplicity, how about an old Nightsun bike light with 12v led par 20's. 

Got a particular flashlight in mind?

Your dc-to-dc converter is a good idea. It all gets into efficiencies of a 12v led light with internals to regulate versus diy. Suppose it comes down to price and availability.


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## Toaster79 (Aug 25, 2012)

Should work. But why use SLA which is very heavy comparing to LiPo. LiPo would be much smaller and lighter.


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## p67 (Aug 25, 2012)

Toaster79 said:


> Should work. But why use SLA which is very heavy comparing to LiPo. LiPo would be much smaller and lighter.



I have a couple of SLAs that I use with 100W incandescent type light now. In the future I could update.


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## p67 (Aug 25, 2012)

I spose I could use an old D cell Mag lite and fit a drop mod from DX like 
http://www.dealextreme.com/p/5-cree...drop-in-led-module-52-7mm-42mm-8-4v-max-35241

And run it off a 6V LiPo or SLA battery. Just wouldnt want to plug it into my ciggi lighter by accident.


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## p67 (Aug 25, 2012)

khergert said:


> how about an old Nightsun bike light with 12v led par 20's.
> 
> Got a particular flashlight in mind?
> 
> Your dc-to-dc converter is a good idea. It all gets into efficiencies of a 12v led light with internals to regulate versus diy. Suppose it comes down to price and availability.



Can you explain the bike light. I am a complete noob, I dont understand half the lingo around here.

D cell Maglites are lying all over the place around here. They would be a good cheap starter for mods.

Also would the max output of 2A current of a simple DC-DC regulator be enough for some of the D cell mag lite drop in mods, like the 5 x White Cree R2 type. They say 1000ma. Is that per LED? or for the whole drop in?


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## p67 (Sep 5, 2012)

These here look like the stuff

http://www.candlepowerforums.com/vb...ifle-Spotlight-for-sale&highlight=scope+mount


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## Gunner12 (Sep 6, 2012)

It can be hard to read those drop-ins, I'm assuming 1A to each LED, but like i say, it's hard to know the actual current to each LED unless you have the drop-in and measure it.

Also, there are many maglite mods around here, a quick searhc should bring up a few. There are also maglite heatsinks for sale in the custom B/S/T forum and IMO they are pretty easy mods to do as long as you have a soldering iron, thermal paste/glue, and a saw.

As long as the driver can take 12+v, you should be fine with hooking them up to the 12v battery.


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## p67 (Sep 6, 2012)

Gunner12 said:


> As long as the driver can take 12+v, you should be fine with hooking them up to the 12v battery.



Okay. So having a 12+V driver would negate the need for a DC - DC step down converter, got it. Cheers.


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## PCC (Sep 6, 2012)

TaskLED sells a few single-mode buck drivers that output one, two, or three Watts of output. Theyre rated for up to 24VDC.


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## p67 (Sep 7, 2012)

PCC said:


> TaskLED sells a few single-mode buck drivers that output one, two, or three Watts of output. Theyre rated for up to 24VDC.



What about something like this [below] using a mag lite as a donor.

SKU 13803



And one of these SKU 12721


And to drive it a [h=1]18V 5W Cree Circuit Board for Flashlights[/h]
http://dx.com/p/18v-5w-cree-circuit-board-for-flashlights-16-8mm-5-5mm-26110

A little bit of knowledge is a dangerous thing.

Am I on the right track?

See Rule #3 Do not Hot Link images. Please host on an image site, Imageshack or similar and repost – Thanks Norm


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## p67 (Sep 14, 2012)

I just hooked up one of these SKU58481 (CREE XML-T6 5-Mode 6700K 900-Lumen Smooth Aluminum Drop-in Module with Textured Reflector) to a fully charged 12v 7AH SLA battery (measuring 13V) and it didn't blow. 

Drawing only 1.25A (not the 3A specified). Specs say its rated 5.8-12V.

Is it likely too die at 13V?

Also, how do you switch between the dif modes using the maglite swtich? Do you have to quickly depress switch and release?


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## yazovyet (Sep 14, 2012)

that dx module specifies 3A output, I'd guess you measured the input. 
1.25 amps at 12 volts = 15 watts
3 A * 3.3 volts = ~10 watts. 
so I'd guess it is generating a lot of waste heat in the driver.


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## p67 (Sep 14, 2012)

yazovyet said:


> that dx module specifies 3A output, I'd guess you measured the input.
> 1.25 amps at 12 volts = 15 watts
> 3 A * 3.3 volts = ~10 watts.
> so I'd guess it is generating a lot of waste heat in the driver.



Correct the input.

I only ran it for maybe 1min. It was getting pretty warm by then.

Will try it out tonite and see how it looks. I also put a DX 50mm aspherical lens on the front. Thinking of using it in the truck, plug into ciggi ligther type mod or run it off the ATV when shooting rabbits.


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## Gunner12 (Sep 15, 2012)

Make sure the drop-in gets enough heatsinking, it's meant to be run inside another bigger chunk of metal (the flashlight that takes the drop-in ). If the LED is running at 3A, it'll get pretty warm, even with a impossible 100% efficient driver.

I'm not sure how long it'll work with 12v, personally I pick things that are higher spec then what I need as long as they don't cost too much, just in case.


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## p67 (Sep 15, 2012)

Well I tested it out last night. Lot of light but even with the aspherical lens not much throw. My Ultrafire UF-007 threw just as far (it has no spill). It will be alright for a general spotlight for possums.


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