an easy way to drop down voltage is to insert a diode into the line. Usually you loose about 0.7V per diode.
You can find diodes supporting several amps very easily and it cost almost nothing. The only issue is the voltage drop is permanent so when the battery goes low you still loose power when it is unneeded.
The top of the regulation is to use a low-drop regulator.
this is a one chip module that can regulate anything with a 0.5v loss. you just need a resistor to set the voltage you want.
They are usually pretty expensive (about 10-15$ ) and must be mounted on an aluminum cooler, but it is still a cheap solution.
I use some of them to get 12V from my li-ion 14.4 cells.

And they are fairly efficient (although I haven't measured one and don't remember the real numbers.

Color temperature is difficult as a spectraphotometer isn't something we normally have hanging around. They are made but the are expensive.

My DSR-300 gives me the color temperature when I white balance it so that's what I use.

<<<-- Originally posted by Mike Rehmus : 4,000 mah (this particular battery) will always beat 2,000 mah, I think.

You will need 10 of the nimh to get to the minimum 12 volts this lamp requires . . . that's $35 and to equal the power density of the LiON, you will need two sets to get as long a run time.
-->>>

one of us has the math wrong... 10 nimh aa batteries @2,000 mah each = 20,000 mah total; but then again, it's been years since i looked at my dc power formulas!

the power density actually refers to how many mah are in equal-sized physical containers... nimh aa vs. lithium ion aa, for instance... i think that's a win for lithium ion, assuming you can get that technology in aa's.

you are right about the current drain, tho... it's not going to be a problem for lithium ion!

i can get 4 nimh aa's + charger for $28 at walmart... so for $90, i can re-charge my entire 20,000 mah power supply in 15 minutes... you'll never be able to do that with lithium ion! there are also covered aa battery boxes available that will clean up the way things look, but yeah, it all has to be custom-assembled.

i've been looking at doing led lighting for the in-car camera rig... i need to match the interior illumination to the outside... i'm running a sony xc-999 lipstick camera mounted to an i/o port rollbar mount, recording to a full-on 6 mb/s solid state mpeg2 recorder, no videotape at all... i built a stereo pre-amp as well, mounted all that stuff to a custom aluminum rig that zip-ties to the rollbar... i think that it'll stand up to just about any vibration.

actually, if you speak about AA cell, it is only 1.2V, so you need to chain 10 of them to get 12V.
when chaining cells, voltage adds up but current (mA) stay the same. to add current, you need to mount all celes in parallel.
you better need to try 3.6v li-ion elements who offers the best capacity versus weigth/size ration.
unfortunately they requires special chargers.
They are easy to find as you can get them for free from defective Laptop battery packs. Most of these packs have one dead element thar renders them useless for the pc, but once dismantled have still enough value to justify the spending into a li-ion charger.

Alright im gonna take the plunge on some "Backup lights" $80 bucks no biggie. If it doesnt work I'll have some big flashlights. Im gonna go to a truck stop and try to get just one. Im gonna follow smoe truckers around and see what they look like. LOL

on second thought, I may just go buy a Britek...

you guys are right about the batteries in series... i'd have to have 20 of 'em to equal that lithion ion pack... ouch!

i have read that lithium ion has an optimal weight/size ratio, so that 3.6v thing makes sense.

is there a dimmable function to any of this? would the color temp change? maybe you could just turn on or off additional rows of lights instead.

Between their rated 14 and 12 VDV operating voltage, the light does change. But there isn't an output control mechanism that really works other than switching LEDs in and out of the circuit.

The problem with that is that unless the LEDs are set up for diffuse light in the first place, you might notice a 'hole' in the light cast by the fixture. the output from a LED is, depending on the lens (which mainly controls dispersion) molded into the top of the LED, very columnated.

Would not the brightest thing to do (pun not intended) be set up the LEDs in arrays that need a low voltage (i.e., no serializing or only in pairs) and use a voltage regulator circuit?

Ultimately, perhaps. But you cannot get too low as the forward voltage requirements of an LED is 3.5-4 volts. So you could chose to put two of them in series and match the 7.2 volts of a camera LiON battery. Maybe. Not very much voltage margin

But the quickest way to get underway with very limited time is to purchase an array of LEDs already in a lamp housing. Without asking for a special product, the lowest voltage range they offer is 12-14 VDC. Makes sense since so much of the world has 12 volts available.

Furthermore, I have not yet found a reliable source of warm white LEDs and don't want cool white for this application.

Beyond that, you have to decide what style of lens you want on the LEDs otherwise they all seem to come with a very narrow beam disbursion which doesn't work too well for videography.

Finally, this lamp came with all the correct LEDs, matched, tested mounted in a standard fixture and, BTW, bi-polar.

A lot of features for a relatively low cost.

Update - The LiON battery has been powering the LED lamp for over 8 hours now and looks like it would run another 8 to 16 hours before the battery reaches depletion.

Good enough for a town this size.

BTW, the battery weighs just over 12 OZ, is about 6" long by about 1.5 by 1.75 inches in cross section with a 4 LED charge indicator. Its output is switchable in several steps between 3 and 12 volts.

Also came with a very nice leather pouch with a belt clip and D-rings for hanging it from a strap. The pouch also has a pocket for the output power cord. Power cord is a coil-cord and will stretch to about 4 feet or so. Charger appears to be intelligent and is a wall-wart. A cigarette lighter charger was included so one can charge it while in the car.

Now all I have to do is complete the enclosure.

Hey Mike I've tried alot of LED's and even have the same LED panel array you have. Are you sure you want to run off only 12V because the output is much higher at 14V with that light. Try it out before you get to far with the housing.

-Brett Erskine

THe housing won't contain the battery, just the lamp, mount and power connector.

The lamp gives me enough light for use in events. I'll probably gen up a 14 volt supply when I get the time. Just the addition of a AA battery in series with the 12 volt battery just about doubles the light output.

After looking at the prices and sizes of the lap top Lith-Ion batteries I decided to go back to the original design and just do two 7.2V Lith-Ion camera batteries. This way I dont have to buy any new batteries or charger and if I dont use them for the light on some shot i can still use the batteries for the camera. I really wish I could find a "voltage doubler" or DC to DC converter that will make it possible to use only one battery. In the mean time Im looking into ELECTRONIC dimmers so that I can effiecently dim the LED's and do it without changing the color temp. Found a kit but looking for a small ready made unit. Otherwise the case is done and looks real pro. Small, thin and light weight as possible. I'll post pics when I rework it with the new/old battery setup. Anyone else busy on this project? What have you been doing?

I just notice this thread and am also a big fan of LED lighting. I didn't notice anyone post up a link to the led museum: http://www.ledmuseum.org/ The guy who runs this site reviews and tests discreet LEDs and *anything* made with LEDs. It is unbelievably comprehensive, most descreets have detailed info including JPEGs of the led's light thrown on a test pattern so you can see the dispersion and any hot spots.
while you are there check out Luxeon Star emmiters. these are very high output LEDs 1 watt and 5 watt models (yes that's right 1 watt), they are a bit expensive (~$20) but have many advantages over using single Nichias or other regular superbright LEDs
Also, I saw somewhere back in this post someone stating that DC-DC converters were not effecient, this is not absolutely true, there are many new ICs designed specifically for driving LEDs that take lower voltages boost to the optimum voltage and provide current limiting, dimming capabilities (through pulsing), and allow batteries to completely used up, because when the voltage drops too low the LEDs will not light and this happens rather abruptly. I think most of these circuits are designed for small LED pocket lights where battery life is a significant concern. Oh also check out the candlepower forums www.candlepowerforums.com (they have been having some problems as of late with their server) Plasmid

Mark, welcome.

Do you have a reference for the LED DC to DC converter chips?

Hey Mike,
Well about 2 years ago I bought ic's(i think they were the LT1932 from linear technologies, discontinued I think, see the lower link, zetex sc310 seem to be popular now) that I thought were 8pin dip packages but for surface mounting to pc boards they were "thin-sot" super tiny things, about 2mmx3mm but they were only a few bucks a piece, could have gotten some board and fabed out some thing, still might, but I got busy doing other things. I just did a quick peek at the candlepower forums and found the link below, $10 for a luxeon driver using similar chips, mounted on a board and ready to go and 1 watt luxeons for $12. I found it in the "Flashlight electronics -batteries included" subforum. Given you interest in DIY I think you'll really appreciate the LED freaks/DIYers there. Search around and you should be able to find plenty of people selling (or directing you to a retailer) everything you could possibly want to put together some kick-*ss LED lighting, and for sure you should pick up a Luxeon Star, you will not believe how small and bright they are, 164,200 mcd@364 mA, versus 11,700@23 mA for a Nichia NSPW500BS, you standard white led.

Anyway the LED driver ics that I bought are somewhere in my house, I got 5 of them so if I find them I'll send you a couple and then all you have to do is get a thin-sot prototyping board from digikey and a couple parts and you can check them out, if you want. I think it's much easier to just find someone who is selling the assembled boards such as the one below... Also be sure to check out the ledmuseum.org, there is a section for links "where to buy leds" as well as tons of links for everything reviewed on the site! Mark


http://www.quality-items-flashlights.com/product_info.php?products_id=91&XTCsid=c43130f4f8fca8ddc8e2da11e4e42d9e

http://www.linear.com/pub/document.html?pub_type=desn&document=295

Nice links, thanks!

I used the Maxim MAX757 for my prototype with 'regular' 6-8000 mCd LEDs:
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1167/ln/en
I followed one of their application notes, and set the output voltage through the divider at 3.5V. There are newer ICs available, but they don't come in DIP packages, only surface-mount. The IC worked great, but I've yet to find true white LEDs without the blue tint...

Hey Roman,
looks pretty cool. I was quite surprised when I got the LT1932s, which I knew were surface mount but didn't realize they were the size of surface mount resistors, but with 8 pins to deal with!! the ledmuseum has a lot of color spectrum info, you might find some less blue whites digging around there. Mark

Some of the blue from the blue LED driving the phosphor usually gets through. Worse is the uneven color temperature near the edges of the beam. That cant be filtered away.
A modern halogen bulb is about the same efficiency as the best white LED's. I know it's fun to play with the LED's, but they do have some issues.
What was the main motivation to use LEDs , other than the novelty?
-Les



<<<-- Originally posted by Roman Shafro : Nice links, thanks!
The IC worked great, but I've yet to find true white LEDs without the blue tint... -->>>

<<<-- Originally posted by Les Dit :
A modern halogen bulb is about the same efficiency as the best white LED's. I know it's fun to play with the LED's, but they do have some issues.
What was the main motivation to use LEDs , other than the novelty?
-Les
-->>>
Portability. Though I've never researched halogen, I assumed it's much more power-hungry than LEDs. Are you referring to regular R20-type halos?

I also wanted to use LiIon cells from junked laptop batteries (most of the cells are intact when the battery is disposed of), and those don't like high currents.

Lastly - YEAH, it's COOL! Too cool, almost blue. :D

P.S. Mark, I think I see a good one, ETG-5CEWHT-35, thanks to your links:
http://www.etgtech.com/update/products/through_hole.htm

Do some research on lamp efficiency, white LED's are just as power hungry as modern halogens, for the same amount of light.

Don't assume!

-Les



<<<-- Originally posted by Roman Shafro :
Portability. Though I've never researched halogen, I assumed it's much more power-hungry than LEDs. Are you referring to regular R20-type halos?

I also wanted to use LiIon cells from junked laptop batteries (most of the cells are intact when the battery is disposed of), and those don't like high currents.

Lastly - YEAH, it's COOL! Too cool, almost blue. :D

P.S. Mark, I think I see a good one, ETG-5CEWHT-35, thanks to your links:
http://www.etgtech.com/update/products/through_hole.htm -->>>

Halogens have other downsides including the weight of their support systems, the heat they generate and the relatively low lifetime compared to LEDs (OK, that's a stretch).

LEDs can also be dimmed with no change in color temperature (that matters).

For a lot of my event work, I need a light to fill in the shadows and pop the color. I don't need 100 watts as I used before. 42 LEDs with an incandescent color temperature, all in a MR-16 package that will run for 3 days on a very small LiON battery pack is ideal.

LEDs even count higher in the comparison when I have to get on an airplane to attend an event and I don't have to ship heavy NiCAD battery belts and large lamp setups.

The small on-camera Halogens don't work very well in the event environment (unless one counts something expensive in the $200+ price range.

Another benefit? People like to talk about the LED setups and for me, that's an ice-breaker with some of my subjects.

Mike, As I stated, the Halogens need the same amount of power as the LEDs. So what extra heavy support systems are you needing for them? Not batteries.
Bulb life? Not a factor, unless you are doing CSPAN recording!
Variable power? Use three small halogens, and switch them as needed.
But it's way more fun to play with LED's , I know ;)
-Les

Les. Here's why I made my LED light.

1)Because of LED are laid out in groups they can be both directional light AND soft light at the same time all the while not having to be diffused. Dont have to buy a mini chimera which would have cut down the power of the light quite a bit.

2)Dimmable without color change

3)None of the batteries life is used up to generate heat. Talent looks good and is confortable under the light. No more burned gells.

4)Modern LED's can be tungsten balanced and dont have any color problems at the edge of the beam

5)You no longer need heavy battery belts to run your light. Just your camera's batteries attach right to the back of the light.

6)More compact light. 1 inch thick

7)Lighter weight/One piece system on top of your camera allowing for steadicam work

8)The bulbs can handle shock much much better than halogens and are rated to last 100,000 hrs. If one bulb burns out your not down for the day nor is the shot ruined.

9)Lower amp draw compaired to a halogen

10)The same light could be adapted to work on light stands for a ultra compact light kit that works DC in remote locations or AC on set.


Every light has their pros and cons. Halogen for example will allow you to do spot/flood where LEDS would have to be rigged up differently. Anyways hope that helps.

-Brett Erskine

Even if we agreed that LED's and halogens are the same I guess the question that really matters is who commercially makes a on camera halogen light that:

1)Doesnt have a hotspot
2)Dimmable/No Color Shift
3)As Soft
4)As Small
5)Runs of your camera batteries
6)Not hot
7)etc etc etc.

Please tell me where I can pick one up because I would have rather not gone thru all the trouble of building something that already exists.

Brett,
How are you getting lower amp draw with the LED's ?
Perhaps you don't need as much light ?
They use the same amount of power as properly selected halogens. Same battery weight. Same AC requirements.
Again, LED's are not battery power savers , lumen for lumen.

Maybe the effort in designing and fabing and LED light is more than designing and fabing a good halogen light.
Apples for apples.

Les,
Interesting discussion. I am certainly surprised that halogens are comparable to white LEDs in terms of efficiency. I was just reading that a mini-mag light draws 0.8 watts on fresh batteries, I'll have to find my 1 watt white luxeon star, as I recall it will dimmly light an entire 12X15 ft room when placed up in one corner, I don't believe the same could be said for the mini-mag, but I am going to check. My question to you is, if in fact halogens and LED are basically equivalent why would I want to design a lighting system where I would have to be constantly replacing burned-out bulbs when I could have one that wouldn't, and have the added bonus not having a hot light fixture. I am pretty sure you knowledge of LED technology is rather dated and I'll bet your "properly selected" halogen bulbs are not cheap, however it seems to me, the most versatile and portable lighting system using currently and easily available technology, would probably use both halogen and LED sources together, each for it's strengths. Mark

PS ultimately using hot wires to generate photons is an aging technology all that heat is just wasted energy, LEDs are just begining to find their way into the mainstream as a basic lighting source. the advances in the last couple of years are simply astounding and will continue.

Mark,
I am fairly up to date on LED's. I designed the LED light source for my 35mm film scanner. I also am a bit of a flashlight-a-holic, and have a couple of 1 watt flashlights as well as a 75 watt Xenon short arc, ala Maxabeam.
It surprised me that the halogens are about as efficient as a good white LED.
For a flashlight that gets knocked around a lot, it makes total sense still, plus I like the blue-green light tint my Luxeons give me.
Sure, hot metal wastes a lot of energy in the IR band, but still, they *do* make a lot of usable photons.
It really sucks when old tech, as boring as it is, still does a great job!
One of the big problems with white LEDs is the color unevenness across the field.

Has anyone investigated small cold cathode fluorescent lamps? I know that the normal household 'compact' lamps make probably 2X the light of an LED ( lumens/Watt ) but they are bulky. Maybe the thin long cold cathode ones are better? They are used extensively in laptops. Hmmm, laptops are power critical... and they don't use LED's either!

-Les

Rather than continue with the he said she said heres real world specs of my LED light:

LED Light
Total Wattage Used: 12watts
Light Output: 350fc @ 1 ft
Light Beam Angle: 60 degrees (perfectly even color all the way across the beam)
Operating Temp: 102 degrees physical bulb temp after 1 hr

Please give us link to a halogen bulb that has better specs

Also laptops use fluorescent like bulbs because of what they are lighting up...the screen. The screen needs to be evenly lit from one side to the other. The bulb as the physical characteristics it needs to make that happen. Have you used a micro Kino before?

Les,
I stand corrected! You should checkout the candlepower forums it's all about flashlights, incandescent, LED, whatever at a very high technical level. Mark

Brett,
have you posted a pic of your light? I would love to see it! This thread is inspiring me to mount up my luxeon for use on my 953! Mark

Brett, I'll see what I can dig up.
Are those the specs for the LED garden light that ledtronics sells? Or are you using one of the trailer lights?
Dimensions of your 12 watt light ?
-Les




<<<-- Originally posted by Brett Erskine : Rather than continue with the he said she said heres real world specs of my LED light:

LED Light
Total Wattage Used: 12watts
Light Output: 350fc @ 1 ft
Light Beam Angle: 60 degrees (perfectly even color all the way across the beam)
Operating Temp: 102 degrees physical bulb temp after 1 hr

Please give us link to a halogen bulb that has better specs

Also laptops use fluorescent like bulbs because of what they are lighting up...the screen. The screen needs to be evenly lit from one side to the other. The bulb as the physical characteristics it needs to make that happen. Have you used a micro Kino before? -->>>

Yes. Its their LED work light. 198 LED's. Although I've altered mine in a few ways to make it work better such as using a 14.4V battery source. Heres a link to some pictures of it.

http://www.dvxuser.com/cgi-bin/DVX2/YaBB.pl?board=Links;action=display;num=1071261354;start=135#141

-Brett Erskine

Don't overlook their 400 LED streetlight. Pricey at $750, Qty. 1 but nice.

LEDTronics brought me one of the garden lights to play with. Very nice and very even. If you had a white plastic shower cap to stretch over it, you'd have a great softlight.

A couple of those and a couple of the narrow-beam MR-16's and one would have a great light kit that could run off a battery you could easily hold in your hand. Or use a battery on each lamp and know that they'd run all day if you want.

I'd be interested in making a panel with a mix of 3000 and 6000 Kelvin LEDs so I could switch color temperatures with a, wait for it, Switch!

Brett,
that panel looks pretty darn cool! Mark

Back from the great adventure with the MR16 LEDtronics 42 LED light.

It worked well. Just enough light to lighten the shadows and pop up the color. Ran all weekend on the LiON battery and a 'C'-sized alkaline to get closer to the rated 14 volts.

I ran out of time to machine a housing so I went to Home Depot and purchased one of the strip-light MR-16 fixtures. I removed the entire light head and U-shaped bracket that holds it to the block that contains the transformer and electronics. That gave me a fairly good looking light fixture with a mount for the top of my DSR-300 (which will accept a 1/4-20 bolt on the handle to tie down their studio viewfinder).

The lamp housing cost $19.95 IIRC and accepts the MR-16 LED lamp directly. Then I spliced the wiring from the battery to the wiring that is supplied with the lamp housing and the job was done.

I did spray the white lamp housing with a dark gray enamel so that it looked more like a Real Professional Light.

The light spread was perfect (the MR-16 lamp is the LEDtronics Medium width version) and would light the area covered by my lens on full wide-angle (which isn't very).

Funny thing was people kept telling me my light was on and I was going to run the battery down.

Would I use this again? Yes. I think it might make a fairly good interview light for on-street use. For that I'll make a power cord that will plug onto the built-in light power socket on the DSR-300.

Anyone have a source for a compatible plug?

The Ultimate in White Led lights for your camera
www.litepanels.com

At those prices, not for me.

Me either, but they are way cool. (no pun intended)

you guys should check out the latest LED technology.

http://www.luxeon.com

Up to 120 lumens for each LED!!!!and they are at 5500 K temp AND at 3300 K!!!!

the luxeon is like a bulbe, not like a panel, then the field given is smaller, and the intensity very high like bulb, so viewing directly at is painful. these are all advantages you get with panels and we should take care when selecting components.

The best would be to select surface mount led , draw a printed circuit. smd led with high power are luxeon that comes either in modules or in smd elements and golden dragon smd leds.
you can see something like this here
http://www.i2systems.com/services/pcb.htm
or here
http://www.primolite.com.tw/products/products_info.aspx?no=LED%20par24-par24&category=07

it looks ok to do it yourslef
http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Number=655078&page=0&view=collapsed&sb=5&o=&fpart=1

i already gave this link , you should find anything you need included luxeon module.
http://shop.dotlight.de/shop/

and if you need to know more about luxeon modules
http://ledmuseum.home.att.net/agilent.htm

and people really mad about flashlights...
www.surefire.com

i think i will use the golden dragon smd led over home made printed circuit and use this heatsink http://www.radianstore.com/plate-fin-dc-converter-heatsink-hs1591eb.html for the back (to give you an idea of the size).
As they come by pack of five, i will build 1 prototype and 4 lamps.
batteries will be li-ion on a separate pack.
The front of the lamp will be very thin frosted acrylic glass (about 2mm). or thicker (5mm) with kind of lens in it to help diffusion.
i think i can use a hot steel ball to make the "lens".
the total thickness should be about half an inch and all sealed in expoxy (for thermal transfer)
cost for 20 leds is about 120 $ + heatsink 10$ + 10$ for misc.
i hope the total under 150$.
The trick will be to make a very thin print circuit, then drill holes to accept the leds, so the led is looking through the printed circuit. then i will isolate the printed circuit with a layer of epoxy or mylar or both and glu the back of the led on the heatsink.(eventually adding a touch of thermal silicon on each led)
the front of the printed circuit can be covered with a layer of aluminium to make a reflector, then the epoxy over. 6 screws are fixing all the layers together.
This idea is not copyrighted, so go ahead and lets compare.

Suggest you use DeltaBond which is a thermally conductive epoxy to fasten the board to the heat sink. Otherwise, the layer of epoxy or plastic will add a thermal barrier between your source and the heat sink.

Don't know where i can find this but google says it is standard
epoxy with 75-85% of alu. oxide.
found a way to recycle my alu. oxide from my miniDV35 project...

Wakefield is the company that makes DeltaBond
http://www.wakefield.com/pdf/accessories.pdf

I will try this, looks better and cheaper
http://www.xpcgear.com/arsiltherad.html
it is epoxy glu and 65 % of silver.

I could even try to get some copper powder and build my own.

this company is selling everything under atomized/micronized form.
http://www.micronmetals.com/silver.htm
and it is cheap....

I just receive my leds.
Finally i ordered 16x 1 watt luxeon (hi output model, because there is 2 versions, the other delivering half the light only).
I choose them for first prototype, because they came mounted on a small alu plate that makes them self-cooled. That means the little plate is big enough to dissipate all the heat. Be aware that is not the case for the 3 or 5 watt models that requires additional heatsink.
The good news is that if you aligne them side by side you will just fill a rectangle exactly the size of the heatsink mentinned in my previous post.
Wiring 4 groups of 4, will make a 13.6 volt/ 1.4 Amps module.
The bad news is, that using the 1Watt model on this heatsink, will limit to 16 leds that would be the equivalent of a 20W lamp.
If I use two modules, this could give a decent light.
Iwill test the heat dissipated this way and try either with 16 x 3W luxeon stars or 24x1w luxeon or 30x golden dragon.
I expect that the golden dragon is a lot more difficult to cool properly.
just waiting for the heatsink now

for info , if you go for the heatsink presented above, note that
http://www.radianstore.com/round-pin-dc-converter-heatsink-hs2070db.html (pin model) has a thermal resistance half of the fin model. for thermal resistance, low value ist best.

On adding diodes to taper off voltage, this is an age old trick. You could read up a bit further and get variable voltage regulators that range from 2 - 37 volts. You have a loss in heat to overcome. That is, you couldn't regulate long at 14v if your input is only 14.4. In fact, that drop probably isn't enough to even make it work. It's been a while since I played with voltage regulators. they come in transistor like packages labeled like LM7805 (5 volts) LM7808 (8 volts) LM 7809 (9 volts), etc.

They create heat and must have an enherent loss to work.

You could use the diodes and put small switches across each one and as the voltage goes in the battery, use a small switch to bypass individual diodes to keep the voltage to the LEDs up.

That's a bit impractical as you now need to add a Volt meter to watch the voltage. Besides, that's basically what a voltage regulator does anyway on it's own.

The best option might be to use the backup lights as they are obviously meant to handle 12 - 14 volts.

Check the actual output of Gel Cells and other battery sources as they are usually a bit over the 12v mark anyway.

As a last alternative, make your own battery packs. You can get the AA sized professional NiMH and NiCad batterys individually. NiCads are 1.2 volts each compared to Alkalines at 1.5 volts each. Rememer to take that difference into account when building packs. Coincidentally, 12 NiCads at 1.2 volts is 14.4 vdc.

You can buy AA battery holders in variuos places for various numbers of cells. Or, you can still get the batteries with solder tabs on them and make an old fashioned belt pack with lumps of soldered batteries in a case.

One quick safety tip. When you start stringing together cells like this, you can get a significant current. Watch for shorts or those little metal cans can get quite hot. In my broadcast engineering days, when you rebuilt a pack of "D" cells, you better remember to check or replace the thermal fuses. A short on those packs can melt lots of things, like clothing, seat covers, carpeting, etc.

Good Luck,

Sean McHenry

currently , there is a lot of ways to deal with problem.
the resistor solution works well when you got steady voltage from power supply (connected on the main) but is bad with batteries of any kind.
the regulator solution is ok but even with low drop regulator as soon as the voltage goes under the specs, it is bad and if you go too high, you just dissipate heat. So basically regulators have same use than resistances, they are just more precise.
The solution if working on batteries is the current pump, a DCD-DC converter with high efficiency (up to 90%).
It makes a steady high voltage (12V for example) from a 3V cell and is able to sucks evey electron out of the cell (the nyou have to take care if using ni-cad or lead batteries that don't like deep discharge)
Most of these converter are single chip, doing all the work with few of them allowing to frive the final stage with an external transistor, allowing high current.
go to google and type "LED driver PWM", you will find a lot of them.

I just receive the heatsink, now trying to find a way to glue the led properly.
I can not get the hand on arctic silver epoxy.
I will try a mix with regular epoxy and alu. oxyde from my mini35 project.