LED voltage requirements??

[Moondog55]

I need a new headlamp and I have been looking on eBay today and I notice that the new cheapies out of China are using a single 3.7V rechargeable AA battery rather than the bank of 3 AAA.
I have one of these from Safeway ( the X-Streem) as my second back-up and I was wondering what the requirements for the 5W Cree LED were, battery life not prime cost being my greatest need at the moment.
If the Cree will run efficiently on 3V I could get a 4* AA battery pack and run the batteries in series -parallel to get a longer burn time

[neilmny]

I think you would find that 3V is too low to get a decent output from the LED.
With AA NiMh batteries they fairly quickly drop below 1.5V per cell meaning that
you would not have 3 volts for long. The 3.7V cell is a LIPo type and holds it's voltage
much better. THe Lipo can only be discharged down to about 2.8 volts but has a much
higher discharge capacity than the NiMh AA's.

[Robatman]

I'd be surprised if they were replacing the 3xaaa with a single aa. Are you sure it wasn't an 18650? They are a common replacement for the barrel type holder for 3x aaa. All of my high power torches and headlamps run on 18650's. much higher capacity than standard aa or aaa.

[Moondog55]

Yes 18650
I was under the impression AA/AAA gave the physical size

[neilmny]

The 18650 is a Lithium Ion battery (not Lipo) and as per my first post operates above 3V through it's voltage curve.
Have a look at this page http://www.candlepowerforums.com/vb/sho ... comparison
you will see the voltage curves for a series of different capacity 18650 batteries.

Assuming your reference to 3V is related to using 2 x AA NiMh rechargeables in series you would start off at around 2.8V and then
drop below that level from there on. This is a voltage curve for them http://www.maximintegrated.com/app-note ... mvp/id/121

[Moondog55]

Do the 3.7 Li-ion batteries offer a viable cost effective power source?
One of them is the same prime cost as a pair of AA lithiums which I need for my little camera, so buying a few may well be my solution.
Is running the Li-ion in parallel a viable option to extend time between battery changes?

[Moondog55]

I am a little confused but having read through most of the posted links is there a general consensus on which battery and which charger offers the best reliability and usable output?

[michael_p]

Neilmny is on the money. The 18650 battery is best suited to this type of usage. Generally torches/headlamps are based on a Cree XM-L LED. The data sheet for this LED is available from Cree's website if you are keen.

Do the 3.7 Li-ion batteries offer a viable cost effective power source?

Yeah, I think so.

Is running the Li-ion in parallel a viable option to extend time between battery changes?

Not tried it myself but it should work.
BTW: When I use two rechargeable batteries together in a device (i.e. in my GPSr) I use them as matched pairs. So I mark two batteries with a permanent marker so I know they go together. I have found that using them as a matched pair works better than using mixed batteries.

I am a little confused but having read through most of the posted links is there a general consensus on which battery and which charger offers the best reliability and usable output?

Having had a variety of different 18650 batteries I can say that there is a marked difference in the performance of different batteries and chargers.

Buy a better charger. From my experience the following charger is much better than the simple plug packs that you can get.

There is a difference in the quality of the batteries. The blue batteries are cheap for a reason. I have had better success with the brown/gold ones. You may notice in the following photo that the brown/gold battery is slightly larger in length and circumference. I read somewhere that the blue ones don't have a protection circuit built in, and they can discharge below the lower recommended threshold, whereas the brown/gold do have protection (the extra length). Don't know if this true but in my experience the better quality batteries are the brown/gold ones.

Hope this is of some help.

Michael.

[neilmny]

Good post Michael. Just want to add weight to the argument for a better quality charger.

Also the Lion batteries hold their charge quite well in storage.
A typical NiMh battery lose a substantial amount of charge even in a month
unless you use something like a Sanyo Eneloop which hold the charge very well indeed
but cost a lot more.

From Google search - http://www.greenbatteries.com/libafa.html#Advantage of Li-ion

"Lithium-ion batteries also have a lower self discharge rate than other types of rechargeable batteries. This means that once they are charged they will retain their charge for a longer time than other types of rechargeable batteries. NiMH and NiCd batteries can lose anywhere from 1-5% of their charge per day, (depending on the storage temperature) even if they are not installed in a device. Lithium-ion batteries will retain most of their charge even after months of storage"

Having said that always top them up before going bush!

[Moondog55]

There is a feller on ebay selling the Panasonic batteries for $34- a pair, my local battery shop wants $37- each, any idea if the ebay seller is legit?

http://www.ebay.com.au/itm/281004345565 ... 1423.l2649

With these LED headlamps what is more important? Current capacity or voltage??
Lighting and my personal safety is one major cost we are prepared for

These seem to offer better value than the Eneloop

[neilmny]

He's sold 490 of them and still has 100% rating. Looks like people like them
or as a minimum actually received them before posting approval.

You can get Eneloops from this bloke Moondog I have both AA and AAA from this one but they are 2000mAh.
http://www.ebay.com.au/itm/320948335761 ... _364wt_728

Don't forget the Eneloops are 1.4V so 2 = 2.8V not 3.7V like the single Lion.

[Strider]

No offense but if lighting and personal safety are so important, I would not be dicking around trying to save cash by constructing something yourself. I would instead purchase something tried and proven off the shelf - a lot less hassle and you can be certain it will work as it is intended.

[Moondog55]

To get what I consider I need of course Strider.
Power source and lighting are (IMO) separate matters.
nothing wrong with Cree XM-L chip

[michael_p]

Just having a wander around the interweb-thingee and found this page on protected 18650 batteries: http://www.lygte-info.dk/info/battery%20protection%20UK.html.

After reading through this page I went and had another look at the brown/gold batteries. They have a ridge down the side and a narrow base which is consistent with the description given as being protected. The blue batteries don't have a ridge or a narrow end. Interesting, I think I'll have to do a strip down when one of them fails.

[Strider]

To get what I consider I need of course Strider.
Power source and lighting are (IMO) separate matters.
nothing wrong with Cree XM-L chip

That is, of course, fair enough. But how confident can you be of its reliability?

[Moondog55]

Of my ability to solder and make battery packs? Very well.

I want something cheaper in the long run than buying non-rechargeable Lithium batteries
I tried this Petzl over winter and the light is no better than a cheap Chinese lamp, and I really do not want anything more than lots of bright light ( Off/On is all I want and need for navigation)
http://www.petzl.com/us/outdoor/headlam ... ce/myo-rxp
What I need is long battery life in case I must walk or climb overnite, no matter what lamp I buy none of them seem to offer 8 hours or more at full beam.

What I don't have the education or experience to determine is whether Voltage or Ampacity is the main need for in getting the brightest light for the longest time.
Both of these can be reached by various arrangements of batteries in series/parallel alighments

Reading and cooking can use any cheap lamp, my local $2- shop sells LED headlamp for $5- that will do that

[neilmny]

If you have a lamp that you are happy with then the best way to get the brightest light for the longest time is to use the battery type and configuration it was designed for.
Don't go to a higher voltage as this will probably reduce how long the LED will live.
The longest time comes from the amp hour rating of the batteries. ie. 2500mAh (milliamp hour.) This means simplistically speaking that the battery can put out
2500 milliamps or 2.5 amps for one hour. (There are many things that influence this and the actual output will more than likely be a lot less)
A more realistic example is if your lamp draws a current of say 250mA (0.25 amps) it should run for approximately 10 hours.
I reapeat there are many things that influence this and the actual run time you get will more than likely be a lot less.
The big influences are quality, temperature, chargeability (how fully they are charging) and load (how much current to run the light.

Solder joints are high risk in my opinion, a good joint is hard to get without stuffing up the battery (from heat which could destroy or reduce capapcity). I consider myself a good
solderer too but I wouldn't risk relying on solder joints in a remote or hostile environment.

I don't know if the above helps Moondog, it probably gives you a bigger headache.

Neil.

[Moondog55]

Hi Neil, soldering onto the driver boards etc, not using solder to connect batteries together. For that I use common plastic packs from eBay or Jaycar.

While I have soldered batteries together it isn't the best solution I admit

[Travis22]

There is a feller on ebay selling the Panasonic batteries for $34- a pair, my local battery shop wants $37- each, any idea if the ebay seller is legit?

http://www.ebay.com.au/itm/281004345565 ... 1423.l2649

With these LED headlamps what is more important? Current capacity or voltage??
Lighting and my personal safety is one major cost we are prepared for

These seem to offer better value than the Eneloop

The blokes name is Yasser.

He's a very honest straight up bloke. Ive bought heaps from him over the last couple years, as have many fellow Australian CPF members. All without any problems.

The Li-Ion cells he sells are the best ones on the market and they will provide easily at least DOUBLE the capacity of the cheap Chinese cells ie. Ultrafire. As a general rule the brands like Ultrafire at least double, sometimes even triple their actual capacity on their labels. So a 3000mAh Ultrafire is actually more like 1000-1500mAh.

The Ultrafire chargers are also pretty poorly regarded and tend to be somewhat hit and miss in how accurately they charge the cells. With Li-Ion cells this is very risky and personally i wouldnt take the chance with them.

Again if you buy from Yasser, his Soshine chargers are much better then most of the others on ebay and generally speaking if you buy a few things from him ie. Charger and some 18650's etc. he will likely either further discount the sale or include some free cells.

(No affiliation, ive never met or spoken to him other then via email. He's in Syd. im in Melb. just a happy customer).

...................

Note, Li-Ion is not 3.7V fully charged it is actually 4.2V

Personally i generally only discharge to 3.5V before recharging my cells at home. Yes good cells can go as low as 2.8V but i always have enough on hand that i dont mind the more frequent charging. When out in the bush i do sometimes run them down till the low voltage cutout kicks in, or the led drivers go unregulated then i change them.

Re: soldering cells, there is a fellow who sells Neo magnets with wires soldered to them. A lot of people use these for connecting to cells for charging etc. But you could easily come up with some sort of holder and simply use the magnets to connect to the cells for the power supply to your led.

Personally, have you looked at Zebralight or Spark. It would be a lot easier for you to just buy one of their headlamps, you can choose from AA, CR123 or 18650's depending on your runtimes. You will not find a headlamp with a better user interface then the Zebralights and a range of output adjustments second to none.



Travis.

[Travis22]

And a quick follow up, regarding voltages and LED outputs.

A single AA is more then enough to drive many of the modern LED's to a very high output and even with a reasonable run time all things considered.

ie. http://www.zebralight.com/SC52w-AA-Flas ... p_109.html

Easily the best single AA flashlight to come out so far (IMO, again like the headlamps they have the highest output + the lowest output = longest run times etc...)

FWIW personally i wouldnt buy from Zebralight direct. Ive had a bad experience in the passed and wouldnt take the chance again with them. If you can buy it locally from an Aussie retailer or even a trusted retailer from overseas i would go that route over buying direct from Zebralight.

Travis.

[Moondog55]

Hi Travis
Thanx for your reply It helps a lot.
I'll check out Zebra lights

[Moondog55]

I think I have stated my original query wrongly and confused things.

I was trying to ask if increasing the voltage supply [ ie: from a nominal 4.5V to a nominal 6V ] would decrease a the current drawn by the LED in the lamp.

The little Cree LM chip ( if I read the data sheet correctly and that is not a given) runs from 3V to 8V and gives ~ 170 lumens per watt. To increase time between battery replacements I was trying to ask if increasing the supply available would give both a brighter light and longer run times.

There are lots of different battery pack options, and I am trying to determine [ by guess work and informed suggestions } my best cost-effective option.

I just want to remind people that while my personal safety takes precedence I am still on a very restrictive budget so a direct Petzl Megalight replacement is out of the question; $100- OK; $550 no-F***** Way and that is what the direct Petzl replacement now costs

http://www.petzl.com/us/outdoor/headlam ... -rush-belt

http://www.petzl.com/us/outdoor/headlam ... ultra-rush

While up at Falls Creek I did try a number of lights, and while the $130- Petzl was the best of those I tried it really didn't give much more usable light that the cheap $17- ebay ones.


If the driver board was on the headlamp section rather than hidden in the battery compartment I would actually buy several of those and just swap battery packs rather than try and change batteries during a storm, easy enough to do using mini MOLEX connectors
So I'm guessing that the problem is not light output as such but finding the correct power supply; 3 * AAA batteries is possible the very worst of all the possible options, 3*AA would be much better
With lithium primary AA at $9- each it doesn't take much usage to make the 18650 rechargeables a valid alternative

[Mark F]

Maybe this is what you need?
http://www.kogan.com/au/buy/portable-rechargeable-10w-led-floodlight/?utm_medium=email&utm_campaign=20130820%20-%20AU%20TIME%20IS%20RUNNING%20OUT%20Fathers%20Day%20Gifts%20from%205&utm_content=20130820%20-%20AU%20TIME%20IS%20RUNNING%20OUT%20Fathers%20Day%20Gifts%20from%205+CID_ca7c8903c41eab7906f0359bcf7eb55c&utm_source=MailList&utm_term=Portable%20Rechargeable%2010W%20LED%20Floodlight

[Travis22]

How the led responds to the voltage applied is governed by the led driver.

Generally speaking the higher the voltage the harder the led is worked, thus the shorter its lifespan.

Depending on the design of the light, installing another battery in series may or may not increase the lights output. Depending on the type of battery and its voltage the overall rise in the voltage could be enough to immediately burn the led / driver out, killing it. If your talking Alkaline, AA, AAA etc. then going from 3 to 4 cells may not kill it but with say Li-Ion, CR123, 18650's etc. adding another cell in series increases the voltage significantly and will likely kill the light.

There are so many variables but just to give you an idea; Take for example your 3 AAA Petzl. It is running 3 AAA alkaline cells in series = 4.5Volts with probably around 1000-2000mAh depending on the brand of cell.
The light would be somewhat regulated to maintain an even light output until the voltage dips below a certain level then it will run unregulated until a specific voltage (maybe around 3V) is reached at which point it wont work any more.

I would say you could pretty safely run a single Li-Ion in place of the 3AAA or 3xAAA batteries. 18650 would be the obvious choice as you want to maximize the battery capacity.

A quality Panasonic 18650 with 3000mAh to 3800mAh would IMO easily double (if not 3x or 4x) the run time you would get from the AAA's and at 4.2V i believe this would still be within the regulated voltage of the light, and if the unregulated voltage or cutoff voltage the light is around 3V then that too will work fine with the Li-Ion cell.

You could even run 2,3,4 Li-Ion cells in PARALLEL, and you would have a hell of a lot of battery capacity there! I think some of the custom headlamps utalize 3x 18650's in a battery pack worn on the back of a head strap. Personally 3 would be the most i would want up there, however i myself would rather just a single 18650 used with the light if its going to be worn directly on the head (ie. not on a helmet).

..........

If you are going to play around with your Petzl headlamp, i would suggest using Protected Panasonic 18650 cells. ie. the Blazar NCRA18650, 3100mAh cell. (No need to get the very latest highest capacity cells (ie. 3800mAh) unless you really want to, you pay a premium for them thats all). The protected cells will protect against over charging and over dis charging, reverse polarity and short circuiting. So that would be a good idea, that way you dont need to worry so much about discharging them to deeply given you dont know exactly how the Petzl leds driver is designed (at what voltage the light will shut off, or the low voltage warning will flash (if equipped)).

The trade off for the protection circuitry is the overall cell dimensions. There are a lot of different dimensions from different brand / model 18650 cells. Protection usually add's a couple of mm to the overall length of the cell. And often protected cells have additional wrapping around the cell so they are also fatter. Granted, if you are just going to make up your own custom holder this should be a problem but its something you need to be aware of if using 18650's in a light made for them, not all 18650's fit in the lights..

Travis.

[neilmny]

I think I have stated my original query wrongly and confused things.

I was trying to ask if increasing the voltage supply [ ie: from a nominal 4.5V to a nominal 6V ] would decrease a the current drawn by the LED in the lamp.

Increased voltage will increase current.
Current is a product of Voltage divided by Resistance.
ie. I=V/R where I is current V is volatge and R is resistance in OHMS.
1 volt/1 ohm = 1 amp
2 volts/1 ohm = 2 amps

[Moondog55]

Travis that is what I have come around to thinking.
2 of the rechargeables on a headband is easy ( I have used 3* "C cells with my old headlamp as well as 3* "D" cells in the belt pack ) and belt packs with MOLEX connectors seem a smart way to do this.

[Moondog55]

I just tried a quick and simple experiment with the $19- headlamp from Safeway.
I bought a 4*AA battery pack from Jaycar ( $2.45 and hooked it up in parallel with the 3*AAA pack, using PURE brand rechargeable cells I get about double the usable light when I do this.
There is enough room in the battery case to mount the driver too if my eyes were good enough to see this fine hook-up wire and with a separate ON/Off switch on the battery pack it would help to stop those annoying accidental turn ons the drain batteries on these cheap lights. With a $19- headlight halving the life of the LED doesn't seem an issue to me, 5000hours is a long time

[Robatman]

Good on you for having a go I say. I tried to make a 5x Cree for a Makita 14.4v battery mounted on a heat sink from a pc. Aesthetics needed some work as well as battery connection(still needed to use battery in drill) but *&%$#! bright!!!

For me a zebralight h600 (18650) is my bush walking headlamp. Massive flood if wanted, but good lower levels for around camp and reading.

While not life and death prefer the quality of zebralight to any of my mods.

Robert

[Moondog55]

Hmm?? I just bid and won an ebay auction for one of these headlamps at $15-, It has one of those AAA adaptor thingies inside it. As soon as i can find a jewellers #2 phillips screwdriver i'll let everybody know if it the same generic driver chip in all the others

[michael_p]

What's the chance of some photos of your project?