9 volt Led

Hi All,

I don't know anything about voltage, amps, etc..., but I'm curious as to why the Led flashlight companies don't try to make the lights more compact by using 9 volt batteries ? (Well ok Pal does). But why don't more. Why would you want to have a long 2 or 3 AA barrel when you can have a nice compact 9 volt barrel ?

thanks,

sylvestor

Agreed. And a single CR123 light before the Arc LS.

I think a two or three AA side-by-side configuration would be better than the popular rod-style. I think putting 3 AA's in a row is getting a bit too long for me.

9 volts? I don't think they have enough juice and they're more expensive (my opinion).

It is probably to do with the simplicity of just banging together 3 x 1.5V batteries, shoving a bunch of LEDs together on a PCB and having a single scraping contact point to activate the whole thing.

Since the white LEDs run on 3.6V - 4V, that would be the simplest. Who cares if the contacts fail before the LEDs rated life is over? Besides, you'll probably have damaged the LEDs long before then with the uncontrolled power supply.

9V and 3V solutions require some level of sophistication. Respectively, step-down and step-up circuits are needed. As many on this forum will attest, these are not the simplest circuit to design and implement, especially if you want high efficiency and/or regulated power. And then there is the problem of size, requiring SMD components and a complete reworking of the manufacturing line to include an SMD soldering machine.

Actually, a pretty simple, compact and easy to make light seems like could be constructed by connecting two 3.6v LEDs together to require 7.2v.

This is exactly the voltage of a rechargeable "9v" battery. Solder the 2 LEDs onto a 9v snap-on connector and presto!...instant, compact 2 LED light.

Seems like that would work...opinions from other knowledgeable LEDers?

I've made a <U>bunch</U> of 2 Nichia LED / 9V "transistor radio" battery lights- They work VERY well with either rechargable NiCd OR primary batteries, without any electronics, not even a resistor.
(I haven't tried using NiMh or the 8.4V NiCd rechargables or with Lithiums- They MAY require a resistor due to their greater energy density)

Longevity is decent (better with alkalines or zinc carbon batteries than rechargables) Brightness is somewhat better than a white Photon.
(NiCds provide higher initial brightness than the alkaline or c/z batteries, but after about 2 hours, the primary type batteries provide more brightness than the rechargable, and after 9 hours, the rechargable is "dead" while the primary batts will go on for a long time)

The higher quality 9v batteries are expensive, and not worth the extra price for this type of application - I buy 2 packs of Panasonic "heavy duty" C/Z batteries for a buck at "The $1.00 Store" or a "six-pack" of Walgreens store branded for three bucks and they work fine.

(I have run LUX/longevity tests on a wide variety of batteries with this configuration, and I'll post them later if there is enough interest.)

There is a simple reason why 9V transistor batteries are not used for flashlights. They have a heinously low capacity... on the order of 50mAh typically with a VERY VERY VERY low (think µamperes) current draw.

That's not quite correct- Most NiCd / NiMH rechargable - 9V batteries are 120 - 150 mAh.

9V carbon zincs are usually around 400mAH.

Energizer alkaline 9V are 595 mAH and their lithium 9V is 1200 mah.

I just checked a fresh "heavy duty" walgreens brand carbon zinc battery and it will run two series Luxeon Stars (with a 1 ohm resistor also in series) at about 250 mA draw for a few moments, (it falls to about 80 mA draw within a couple of minutes).

My freshly charged GP brand NiCd does better with the two series LSs- it starts out with about 450mA draw, and after ten minutes, is still supplying 200mA... after 20 minutes, I'm getting 40 mA draw...and after a half hour, the two LSs still put out more than enough light to get around in the dark (8 LUX @ 1M .... and even after an hour and 20 minutes, I get 5 LUX)

Now, I'm not saying that 9V "transistor radio" batteries are ideal for high draw devices like conventional flashlights (or even LS or LED flashlights with more than two Nichias).....
Just that they aren't quite as bad as you claim they are...

And my experience with them powering 2 series Nichia LEDs has been quite good.

After 12 hours of continuous use in one of my tests running off of a 50 cent Walgreens 9V carbon zinc, the 2 Nichias were still putting out 5 LUX (measured at one meter), with 6.8mA @ 6.24V--- enough light to easily get around in a dark house. And after 260 continuous hours it was still putting out enough light to read with (not comfortably or efficiently, but you could read with the LEDs about 4-6 inches away).

I would love to the see the run time tests. In addition, a little more directions/photos on those homebrew 9V lights would be great.

Joe S.

Also...if anyone has a project like this, and has figured out a compact enclosure for the light...that would be nice to hear about (or see!).

OK-
There are many real easy ways to make these, and dozens of possible enclosures-

This is how I make mine:<CENTER>



</CENTER>
The pictures are pretty much self explanitory.

The original purpose behind these lights was as a backup mining / caving light.. They can be attached to a helmet / hardhat with small screws, double-sided sticky tape or Velcro (which is what I use). But they also work fine as a hand-held pocket/backpack/purse light.

I chose not to use a switch at all for simplicity and reliability. Just insert the battery to make light, remove battery to make dark.

I tried several different kinds of battery holders-
THESE FROM MOUSER seem to be the best for strength, battery holding power and overall reliability- Plus they are cheap.

The aluminum channel stuff is to protect the LEDs and to act as a heat sink.

{The aluminum channel is available at most any "real" hardware store- I think I paid about $5.00 for an eight foot section (of course you only need 3/4 inch for one light, so maybe you can scrounge or substitute) You might even be able to do without it completely, but with the first ten minutes with a new battery the LEDs do get pretty hot.}

9V 2 Nichia LED Light output / longevity tests:

Number on far left will be hours of continuous operation.

Letter will indicate which battery: R= GP brand 7.2V NiCd rechargable; D= Duracell Alkaline; P= Panasonic "general purpose" carbon/zinc; W= Walgreens store brand "Heavy Duty" carbon zinc. M=2AAA Mini-mag incandescent with fresh AAA Eveready alkalines for comparison.

The following figures are the LUX reading from 1 meter / LUX reading with light in contact with the light meter sensor.

There will be some discrepencies: NM= not measured.
Sorry this isn't neater and more concise- the Walgreen's test was done at a different time from the rest, and neither test was done on a regular schedule, just when I had a chance to measure.
Also, I probably ought to re-run the test with the rechargable- It may not have had a full charge then, and I have noticed better stats with them lately...
_________________________________________________


0 (fresh batteries) R= 38/16,300 : D= 27/13,400 : P= 34/15,000 : W= 35/NM : M= 140/18,000

1 W=20/NM

2 R=22/11,000 : P=24/12,500 : D=32/14,600 : M=60/17,000

3 W=15/NM

3.5 M=0 ("dead" batteries in mini-mag)

4.5 R=2/600 : P=17/7,000 : D=28/10,200

9 R=1/174 : P=9/4,300 : D=17/7,600

12 W=5/NM

14 R=0/75 : P=6/2,700 : D=7/3,600

17.5 W=3/NM

19 R="dead" : P=4/1,658 D= 4/1,730

23.5 W=2/NM

27 P=4/1600 : D=3/980

34.5 W=2/NM

39 P=1/510 : D=1/525

48 W=1/NM

61 P=1/340 : D=1/430

119 W= 1/200

Even after over 200 hours all the primary batteries had enough "juice" to put out 1 LUX at 1 meter- Enough light to read by, and if you are in total darkness with eyes adapted, you can get around without too much difficulty.

Here are some beam comparison photos so you can see what these 2 Nichia / 9V lights are like compared to a 2AAA Mini-Mag- the first pic is with fresh batteries, and the second is after 2 hours of continuous "burning". (The focus on the Mini-Mag is adjusted to best match the "dispersion" from the LED lights, not for tightest focus/brightest spot)


Also, regarding one of my earlier posts on this thread- Concerning the 2 series connected LS LEDS-
After 8 hours of continuous operation on a Walgreens C/Zn battery, I got 15 LUX @ 1M with 8.6mA @ 5.27V.
And after 20 hours I'm getting 6 LUX @ 1M with 5.17V @ 5.0 mA- (This IS more due to the amazing efficiency of the Luxeon Star than the battery's qualities, but even I am amazed at this). WOW!

I built one of these 9V lights with 2 Nichia whites in series + dropping resistor. I used a RS rocker switch. Also used an Ledlight.com reflector over each led. The light looks like a snake-eyes.
Works VERY well. It all fits in the palm of my hand and is VERY bright- as led lights go. I recommend the led reflectors.

Where can I see a photo of the reflector?

Is this the place?

Reflectors and LEDs

How much light difference is there between an led that pokes through a plastic box and only sticks out about 50% compared to one that's mounted inside a reflector?

What's the current flow from a 9v battery with two leds in series?

Looks like better performance than a 2 AA maglight.

Would a Plainview 9.6 NiMH provide enough output to drive 3 LEDs in series? Using only two and burning the remaining power as heat in a resistor does not make much sense.

A nice design would be a really small clip-on where the battery itself is the handle (or stand). How to switch it on/off? Would make a nice lantern, too, if light output were diffuse and perhaps dimmable. Hmm...

It's a nice light. Like you say, for all practical purposes, it works fine.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
[QB].....
What's the current flow from a 9v battery with two leds in series?....
[QB]<HR></BLOCKQUOTE>

I haven't done a lot of testing on this as it is kind of a hassle to measure with my designs, but here are the figures I do have:
(no resistor in my circuits)

Walgreens "heavy duty" batt (9V nominal):
Fresh=9.29V no load, 8.0V @ 87mA under load.
(This is WAY above specs, but it doesn't last long- a couple of minutes)
12 hours= 6.24V @ 6.8mA

GP NiCd (7.2V nominal):
Fresh charge= 9.34V no load ; 8.8V @ 120mA under load.
(This is even further above specs, but it does fall quickly)
1 hour: 8.24V no load ; 7.1V @ 27.5mA under load.

YES- running these things without a resistor does significantly over-drive the LEDs for a while. That is why I use the aluminum channel as a heat sink. However, I've made a dozen of them with this configuration and "burned-in" all of them with at least 2 full cycles each and never had a "melt-down".

It probably does reduce the life of the LED somewhat- I don't think it would be significant though- even if it cuts the life in half, that is still five years of continuous operation.

Ideally you would want to have a resistor in series during the first few minutes of use, then a bypass switch to get the most light out of the battery after the current falls to more reasonable levels.

Or you could go the PAL route and put in controller circuit.... but that kind of defeats the purpose of easily homebuilt simplicity. In that case, you might as well just buy a PAL.

Just for those that are interested in extreme battery life / light output:

Those two series connected Luxeon Stars (with one ohm resistor) on the Walgreens 9V C/Zn battery: after about 75 hours continuous operation- I'm getting 2 LUX light output, measured at 1 meter, and it is sufficient light to get around in the dark (even with un-adapted eyes).

Those LSs are amazing. I can't wait for the lambertian units.