S.O.S. What is most efficient 3XAAA battery configuration/driver for 1 XP-G @ .5A?

[Den Den]

I am a novice who would like to benefit from your collective wisdom. I am a runner, and my schedule has me running well before the sun is up. I use a 3X AAA headlamp with one very dim LED. I want to upgrade to one XP-G LED, and run at 500mA (Vf 3.1V and approximately 190 lumens) for at least 2 hours. I must (I want) to keep the 3X AAA format, so I have only 4 battery configuration options:
1) 3X AAA NIMH Parallel 1.2V @ 3600mAh (boost?)
2) 3X AAA NIMH series 3.6V @ 1200mAh (boost/buck?)
3) 3X AAA Li Ion Parallel 3.6V @ 1050mAh (boost/buck?)
4) 3X AAA Li Ion series 11.1V @ 350mAh (buck?)
I gather that buck drivers are more efficient, but if a 11.1V Li Ion has only 350mAh, would the buck driver allow 500mA for 2 or more hours?
I appreciate any and all help you may give me.

Signed,
A frustrated and confused novice.

 

[Jash]

Mmm...Why not just get a Fenix HP10?

 

[Den Den]

Well...for one, I'm not independently wealthy! But more importantly, I am excited about upgrading my existing light (this will be my first mod). That is why it will be 3X AAA; the only thing I want to change is the emitter and corresponding driver.

 

[ti-force]

I think you would probably get more answers in the Homemade and Modified section, but here goes.

First of all, you should have a look at a very useful driver page by CPF member Torchboy. It's located right here.

I don't know how much room you have to work with (diameter and thickness of driver), but here are some options.
If you want to run 3x Li-ion in parallel, or 3x NiMh in series, you could run a linear regulator driver. e.g., a shiningbeam 1.4A 3-mode driver ($6), just remove two of the 7135 chips (each one increases current out by 350-400mA), so if you remove two(there are four on the board), you would have a total of roughly 700-800mA battery draw on high(less than that to the emitter), roughly 219-251mA on medium and roughly 30-34mA on low. But the high might be too high and the other levels might be too low for your needs, so you might be better off leaving all of the 7135 chips on the board and switching to medium mode which would be a battery draw of roughly 440-503mA. High would be 1400-1600mA and low would be 60-69mA.

These drivers aren't a good choice for an emitter that has a high Vf, but fortunately, I think most XP-G emitters have a pretty low Vf, so this driver should work well. Recently, I modded one of my Quarks (XP-G) with the SB driver. My XP-G measured a low Vf of 3.08v, so it should run in regulation until the battery is depleted. V in must be .12v over Vf of LED, if not, the driver drops out of regulation. Minimum V in for the driver is 3v and max is 6v, but like I said, V in must remain .12v above Vf for the driver to remain in regulation. Also, the higher the voltage, the more efficiency will drop.

You can also buy this type of driver from Deal extreme or Kaidomain. They're called AMC7135 drivers from those two dealers, and they come in all different flavors. e.g., multi-mode, single-mode, 750mA-2800mA, so the choice is up to you. Personally, I would go for the SB board because they are right here in the U.S. and they ship very quickly, but I'm not sure if a 7135 based multi-mode driver will work with your setup or not. Mode changing for the SB board works as follows: The light must remain in the desired mode for at least 2 seconds for mode memory to take effect. If power is cut before the light has been in the desired/selected mode for 2 seconds or longer, the next time power is applied, the light will come on in the next mode. If the light has been in the desired/selected mode for longer than 2 seconds and a mode change is desired, you simply turn the light off, then do 1 short press and then 1 long press. Basically, your just cutting power, then supplying power for less than 2 seconds, cutting power again and then turning the light back on.

Check out the driver list for other options.

 

[jorn]

remember that the xpg needs cooling. i dont know what kind of "very dim led" the headlamp original got, but if its a 5mm type led, you defently need to mount the xpg on some sort of heatsink. I see youre not planning on driving it hard, but i still think heatsinking would be needed.

 

[Den Den]

Thank you for this information, it is appreciated. I will certainly use a heat sink. Will it work to use 3X AAA Li ion parallel, 11.1V @ 350mAh, and buck with a buckpuck 500? If so, what kind of run time could be expected? Also, is it possible to move this thread to the correct forum for greater exposure to the right audience?

As always, any input is appreciated,
Thanks, Dennis

 

[ti-force]

Thank you for this information, it is appreciated. I will certainly use a heat sink. Will it work to use 3X AAA Li ion parallel, 11.1V @ 350mAh, and buck with a buckpuck 500? If so, what kind of run time could be expected? Also, is it possible to move this thread to the correct forum for greater exposure to the right audience?

As always, any input is appreciated,
Thanks, Dennis

When batteries are used in parallel, the voltage stays the same but the capacity multiplies. e.g., 3x AAA Li-ion (3.7v, 350mAh) in parallel = 3.7v with 1050mAh. When batteries are used in series, the voltage multiplies but the capacity stays the same. e.g., 3x AAA Li-ion in series = 11.1v with 350mAh.

Three AAA Li-ion in parallel would give you a longer runtime. 1050/500 = roughly 2.1 hrs. of runtime vs 350/500 = roughly .7 hrs. or 42 minutes of runtime. You need to look at the minimum V in for that driver. If it requires a minimum V in of 5v, then 3.7v from three AAA Li-ion in parallel isn't enough.

As for moving this thread to another section, you will need to contact a moderator, or if they see this thread and deem it misplaced, they may choose to move it.

 

[Den Den]

Message recieved...and I said parallel when I should have said series. So in series, Li ion 11.1V @ 350 mAh's, so if I want to drive XP-G (Vf 3.1) at 500mA, will using a buckpuck 500 work? And if so how long?

Again thanks, any information is appreciated.

 

[ti-force]

Message recieved...and I said parallel when I should have said series. So in series, Li ion 11.1V @ 350 mAh's, so if I want to drive XP-G (Vf 3.1) at 500mA, will using a buckpuck 500 work? And if so how long?

Again thanks, any information is appreciated.

It will work, but the runtime will only be 42 minutes roughly. 350/500 = .7 hrs. or 42 minutes of runtime.

 

[Den Den]

Thanks for the response...so is there any way to achieve 500mA to an XP-G (3.1Vf) for at least 2 hours utilizing only 3X AAA batteries (any configuration and with any driver)? That is my question. And if the answer is no, then which configuration/driver provides 500mA for the longest duration of time?

 

[ti-force]

Run 3-Li-ion batteries in parallel or 3- NiMh's in series with this driver. When you turn the light on, set it to the medium mode which will be 440mA and leave it there. 440mA is pretty darn close to .5A.

 

[Den Den]

Message recieved...thank you for the link. Any guess as to how long it would be powered at 440mA? And is there any benefit runtime wise between Li Ion v. NiMh? (If just a toss up, NiMh would perhaps be safer and easier, Yes?)

Again, thank you.

 

[Den Den]

p.s. that is one spooky looking candle...foot candle...I get it...but I am still going to have nightmares!

 

[Lynx_Arc]

Run 3-Li-ion or 3-NiMh batteries in parallel with this driver. When you turn the light on, set it to the medium mode which will be 440mA and leave it there. 440mA is pretty darn close to .5A.

unless the driver specs are incorrect it won't run off 3 parallel nimh cells, 3 series should be no problem at 2.8v-6v, and at 6v it wont run 3 lithium ion in series so to use nimh and lithium you would have to wire them in separate configurations otherwise you would need a driver to handle 1.2-5v range for both in parallel and 2.8-12v approx for both in series.

 

[ti-force]

unless the driver specs are incorrect it won't run off 3 parallel nimh cells, 3 series should be no problem at 2.8v-6v

Yes, you're correct. It was getting late, so I made a typo. I stated all of this correctly in my first post, but thanks for pointing this out; I could have mislead someone and I don't want to do that.

, and at 6v it wont run 3 lithium ion in series so to use nimh and lithium you would have to wire them in separate configurations otherwise you would need a driver to handle 1.2-5v range for both in series and 2.8-12v approx for both in series.

I explained this in my first post also, so I was just trying to give a quick description in my last post:thumbsup:. It just so happens I made an in my previous post.

 

[ti-force]

Message recieved...thank you for the link. Any guess as to how long it would be powered at 440mA? And is there any benefit runtime wise between Li Ion v. NiMh? (If just a toss up, NiMh would perhaps be safer and easier, Yes?)

Again, thank you.

I made a typo last night, but it's cleared up now. If you want to use AAA NiMh's, you must run them in series using the SB driver. So, if your AAA NiMh's have a 1200mAh capacity, like stated in your first post, and the battery draw is 440mA, the runtime should be 1200/440 = roughly 2.72 hrs. (2hrs and 43.2min.) of runtime.

If you run three AAA Li-ion's in parallel, and each has a capacity of 350mAh, the runtime should be 1050/440 = roughly 2.39 hrs. (2hrs and 23.4min.). I think you should probably run the NiMh's for simplicity. You won't have to make a parallel battery holder or anything, plus if these batteries will be up against your head, the NiMh's will also be a safer option. You get a longer runtime with the NiMh's too.

p.s. that is one spooky looking candle...foot candle...I get it...but I am still going to have nightmares!

Be afraid, be very afraid Just kidding:candle:

 

[waddup]

buy one of these,

you can get a great light for $15.

https://www.candlepowerforums.com/threads/260052

or the

https://www.candlepowerforums.com/threads/240639


^single AAA great quality with 3 modes $20; perhaps THE best deal in flashiIght history?



by the time you actually get your parts and IF they are working and IF you can get them into your project still working you might as well have spent a few extra $$ and got something off the shelf that is already excellent.

 

[Essexman]

With 3AAA I wonder if you could use a 500mA Micropuck in buck config ?

The micropuck is bulletproof, samll and easy to wire up.

Although the micropuck is a boost driver it can be wired in a number of ways, see HERE for spec sheet.

Edit - Arh crap, luxDrive have changed the website and I can't find the old data sheet that showed you all the configs for boost, buck, buck - boost!!!!


Another Edit - wiring details here on the cutter site.

 

[LEDninja]

Before we destroy the original headlamp let us check a few things.

Is the original battery holder series or parallel? It would be impossible to change that around without destroying it.

Is there a driver? Most dim (cheap) 3AAA/3AA flashlights/headlamps don't, they just direct drive. If you are real lucky there might be a dropping resistor. Hint: If it has multimodes, strobe, SOS it has a driver. 2 levels probably just different resistors with a 3 way switch.

It might simply be replacing the dropping resistor if it has one or adding one if it has none. Calculate the resistance value from many online calculators such as
http://www.pcboard.ca/kits/led_notes/
Use NiMH to keep battery voltage fairly constant.

BTW the micropuck output varies with voltage so you don't get flat regulation either.

 

[Den Den]

Thanks for all the input. The options for a micropuck at 3.7V input are not that attractive. http://www.ledsupply.com/docs/MicroPuck-Applications.pdf Assume I can make any necessary modifications (series or parallel battery holder), and also assume I don't want to buy a new light (despite the low cost). I just want to know the most efficient way to introduce 500mA to one xp-g if all I have to power is 3X AAA batteries (I was hoping for at least 2 hours run time). I wouldn't have thought that using a resistor to steal current could ever be considered efficient, but with 3X AAA as the power source, it is looking like direct drive with a resistor is the best option...but I would love for someone to show me a better way!