quad lux III off common batteries?

I'm wanting to build a light for a friend (non-flashaholic) using the PQS and Lux III emitters, but it needs to run off common batteries for it to be useful to him. I haven't done anything with a boost driver before (like a fatman or shark) but I think that wil be the best way to go on this one. I'd really like to use 3 C or D alkaline batteries for this light, but am having trouble figuring out if I can drive 4 lux III off of this low voltage.

As far as I can tell, I can use a fatman and 2-3 alkalines (min Vin 2.7V) and drive the 4 lux in series since it can output up to 16V. But what I can't figure out is how much current I can supply when the output voltage is that high (will be around 14.5V). Can I still supply 0.8 amps or higher with this big of a difference between Vin and Vout?

Is there a better driver to use for this type of configuration? Am I trying to do something impossible?

Thanks for your help,

schiesz

schiesz said:

I'm wanting to build a light for a friend (non-flashaholic) using the PQS and Lux III emitters, but it needs to run off common batteries for it to be useful to him. I haven't done anything with a boost driver before (like a fatman or shark) but I think that wil be the best way to go on this one. I'd really like to use 3 C or D alkaline batteries for this light, but am having trouble figuring out if I can drive 4 lux III off of this low voltage.

As far as I can tell, I can use a fatman and 2-3 alkalines (min Vin 2.7V) and drive the 4 lux in series since it can output up to 16V. But what I can't figure out is how much current I can supply when the output voltage is that high (will be around 14.5V). Can I still supply 0.8 amps or higher with this big of a difference between Vin and Vout?

Is there a better driver to use for this type of configuration? Am I trying to do something impossible?

Thanks for your help,

schiesz

Click to expand...

If you just want a cheap setup that works...

I have been using AMC7135 LDO's...you could easly make a driver to drive the 4 LEd's off of 3 or 4, C or D cell...

Check out this post

So you would build 4 parallel drivers... you could also have a high low switch...switching from 350am-750ma or whatever...

Cheap & easy to make but not *** eff as the fatman...

enjoy

Ktronik

4 is really out of the question unless you go for like a 6D light.. however.. i have built an ok solution with 3 luxes and 4C in a 3D and a tube.. use a fatman and set the current to about 700mA.

alkaline bats just do not have the current capability to push the likes of the power you are looking to drive.

the 'math' for fatman.. you have to make sure you are lower than 2.2A input.

So.. for 4 lux.. that's about 3.5V x 4 = 14V.. now if you want to drive them full power.. that's 14W.. now.. divide by 90% and get 15.55W input into the driver.. the max current to fatman is about 2.2.. but 2 is a better number to use to give some headroom.. so divide by two.. 7.78V is the MIN. voltage required..

under the draw you are describing (2A from the batteries).. i would not expect to hold more than 1.25V from even D cells.. means you need 6.22 cells..

now.. re-work with 3xlux at 700mA..

.7Ax3.4Vx 3/.9 = 7.93W input.. to drive 3x lux3 (Jbin) at 700mA.. round that to 8 and divide by 2 and get 4V minimum.. that's far more doable.. if you have 4xC and put them in a 1" pvc tube you can get a fairly decent output.

you just plain can't have max power and a crappy powerplant.. that's the trade off.. about the best you can do from alkaline is exactly as i just described.

Now.. if you switch to lithium primary.. and use a tri-bore light.. you can put the likes of 3x3 lithium primary CR123 into a 2D light.. you will have the likes of the 7.5V.. which is really close to pushing 4xlux3.. you'd just have to dial down the output.. maybe 830mA (my fav. setting .. that is 3W).

so.. 3W x4 =12 /90% = 13.33W input.. divide by roughly 7.5V and get 1.78A (less than 2.0 so you're good).

that's how i would go if you want primary.. the other option.. is AA primary.. you can even use a non-bored light then.. 2D from 6AA = 1.25vx6 = 7.5V.. and they can handle 2A also. you will need the likes of the FM or modamag 6AA ->2D adapter.

runtime should be pretty nice.. and manoman are maglights LIGHT when filled with lithium primary cells! I have a 9AA light that uses lithium primary.. but it's a hotwire.. over 500Lumen out the front!

Go take a look at 'BAM!' in my signature.. since it runs from fatman.. it will follow the same rules.. but will be a 90 second installation vs an all day operation to create it.. depends if your friend can wait 2-3 months to get one.

-awr

Thanks for the replies, you two (Ktronik and AWR) are the best when it comes to these applications. You can't ask for a better response than from both of you guys!

I've been reading your posts for a few days straight specifically for this, trying to see what to do.

I must be pretty dense because I am having trouble making heads or tails out of your post about the LDO driver Ktronik, and i've gone over it many times over the last few weeks.

I really want a BAM from AWR, but you keep wasting time on those nanos...:naughty: oops, might have to duck after saying that!

Thanks again guys, i'm going to keep working on the LDO drivers to see if I can figure that out. I'm trying to keep this one fairly cheap, as I have a bunch of emitters sitting around right now begging to be used. I was willing to spend some money on a battery holder, or on a driver board, but adding both is more than I can put into this project. Now, for MY next light, the tri-lux U-bin, that will be a different story .

schiesz

There is a really neat chart on direct drive solutions.. which emitters work with what type and quantity of cells.. if you keep your drive levels reasonable.. i'm betting there is a nice solution for you.

that little LDO chip is nice.. IIRC it's 350mA so he's using two in parallel to get 700.. it's a very smart thing to limit current.

The nano driver will do the same thing and can be tweaked up over 1.5A so rather than paralleling the chips you can parallel the emitters.. two nano drivers can run 4 emitters.. but a fatman ($22) will be cheaper.. it's defnitely the best route to go... far less work and it just does the job right.. if you don't mind a protruding pot handle it's unbeatable to have a 'dial your brightness' function.

-awr

The DD reference that I know about is this: https://www.candlepowerforums.com/threads/79520

which I have used in the past, but unfortunately it does not cover quad lux configurations. It seems to be quite accurate for single and tri lux however, as I have used it for making a few lights already, including fathers day presents for mine and my wife's dad.

I have heard, however, that 4C in a DD quad lux in parallel drive it fairly well.

schiesz

the problem with 4C -> quad lux.. is you'll be trying to pull 3-4A from alkaline Cs.. they aren't happy with even 2.. what ends up happening is a drastic reduction in watt-hour output as 1/2 the power goes into heating the batteries.. you will likely get more light from a 3-emitter solution.. the lower the drive current with LEDs.. the more lumen per watt... truly a case of 'less is more'.

-awr

Thanks once again for the input Andrew, i'm going to have to re-think my plans once the PQS gets here. I haven't used that heatsink before, so i'm not sure if I can use it to mount 3 emitters, although i'm sure I could do it with 2 and just leave 2 of them off. I'm assuming the PQS slightly elevates the emitters to allow the IMS relfectors to work without modifying them.

schiesz

hmm.. the PQS has four posts for mounting.. you can still use four.. here's a neat possibility.. just get high enough vF so the current draw is lower.. 500-600mA.. that will pull 2A-2.4A.. a painful but tolerable level of draw from C alkaline.. or you can use it in a 3D and the D size should deal with that.

the lower the current.. the more lumen per mA to the emitter... so.. four emitters at 2W each or 8W.. will likely be more output than 3 emitters at 9W or 3W each.

3 cells will probably pull down to 1.2-1.3 pretty quick.. so 3.9V.. My UX1L run at about 3.9V.. so an L, or M emitter might work out perfectly w/o a resistor.. direct-drive and give you a really fun 'wowza' burst of afterburner with fresh batteries.. double check the current draw though.. might need a resistor.

-awr

What is the danger of too high a draw from the alkaline battery? I know the issues with driving the lux to hard, and the dangers of drawing too many amps from a litium ion battery, but am not sure what will happen if I try to draw too much from alkalines. I got these emitters cheap and have a bunch of them, so using a higher Vf luxeon is not going to be possible on this light.

I have been playing around with this build the last few nights, got the emitters mounted and the reflectors cut to fit in the head, and tried a DD from 3 D and 4 C. I measured the current at one emitter and got 8 amps with the C config, which scared me, so I switched to 3 D and still measured 7A.

So I think I may be measuring the amps incorrectly. Is it appropriate to measure current on the leads of the lux? I measured at the point where I connected the 4 lux in parallel as well, and got the same results.

Again, I may be dividing where I shouldn't or something, but this leads me to believe I am driving the LEDs at 1.75A each (too high), and drawing 2.3A (maybe ok) from each D battery.

I am pretty excited about this light because its a gift for a friend I haven't seen in a long time, and I didn't have much funds to spend on it buts it seems to be coming out pretty well.

Total cost is an unbelievable $30 right now. If my calculations are correct about the 1.75A per emitter I am going to have to put some resistors in there, but otherwise I think thats going to be the grand total. Thanks TekTite for making this possible with your $1.25 luxeons (even if you did send the lambertians by mistake).

schiesz

How did you measure the current? if you have all four wired up already you need to measure the current at the tailcap.. if you attempt to measure current as if you'd measure voltage.. what you are actually doing is shorting out the emitter through your ammeter and just pulling max current from the battery.

In-light current measurement:

remove tailcap
turn on light
set meter to DC A.. (10A).. make sure leads are in the correct jacks
touch Neg lead to bat - inside light
touch Pos lead to bottom edge of battery tube.

(press quick and hard.. if it's high-resistance it'll generate a lot of heat).

The batteries are all in series.. whatever current you pull from one it's from all of them... if.. you are measuring 2.3A from the battery.. you are only getting 2.3/4 = 575mA to each emitter.

looking at the C-size datashee from duracell.. we can find out a few things..

1) 150mohm resistance.. means that for every amp you lose 0.150V.. if you pulled 8A from a C size battery you'd get (1.5 - 8 x 0.150) = 0.3V remaining.. so you didn't pull that one off.

2) The only rate up to 2A rate.. but at 2A.. they show 0.3hours to 1.0V and 0.5hrs to 0.9V/cell.

So.. let's stay within the rated values as an example.. if you tune the thing 'til you get say 2.0A from the batteries and 500mA to each emitter.. the best you can expect is 30 minutes of sharply declining output.

Looking at the D size.. you'll get over 1 hour to 1.0V and more like 1.7hr to 0.9V/cell.. but that means.. with 3D.. the voltage will drop to 2.7V in about 90 minutes.. and the voltage will drop continuously from the start.

I built a light similar to this concept with 3 luxe's and tried to run it with 3D and they didn't have the voltage to get 700mA to each lux.. I re-worked it to use 4xC in a 3D host.. and now it will regulate (with fatman) 700mA with fresh batteries.. but the math works like this:

at 700mA it takes about 2.5W per emitter.. and that means 8.26W from the batteries.. at 1.5x3=4.5V that means 1.83A to pull that off.. bump that up to 4 emitters.. now you need 11W from the batteries and at 4.5V that means 2.44A from the batteries.. the problem is.. that's fresh batteries no load.. more realistic.. you'l get 1.25Vx3 = 3.75V fresh and 3.0V toward the end.. and that means starting current of 2.93 and ending current of 3.67 for 4 emitters.. and 2.2 to 2.75A with 3 emitters.. so.. with fresh 3D you can JUST regulate 700mA.

now.. using 4xC instead:

with 3 emitters.. the input current will range from 1.65 to 2.29A but with 4 emitters the input current will range from 2.24 (upper limit) to 3.11 (not doable).

Those are all values figured with fatman driver..

running unregulated.. you will not be getting nearly the output you deserve... i most certainly would not try to run more than 3 emitters.. the more current you try to pull from the bats.. the faster the votlage will drop and output will suffer a LOT.. You will likely get more light from 3D x 2 emitters than 3D x 4.

Get some accurate tailcap current numbers and wait for the current to 'settle in'.. the voltage on the bats will drop dramatically when you first turn it on.

Also.. measure the voltage at the emitters (all will be the same if parallel so just measure one)..

What is the Vf of the emitters again?

From my experience, the happiest solution you'll find will either be a 3 emitter fatman solution.. or a 3D x 2 emitter direct-drive solution. It does depend on the vF of the emitter.. but with 2 emitters.. DD from 3D.. vBat will range from about 3.75 down to 3.0.. and with Jbin emitter that would be a range of like 1A / emitter down to 122mA/emitter (with dead bats).

With 2 emitters.. you can use the PQS and have the alignment be symmetrical.. also.. you will push the emitters at 1A and get on the order of up to 90L/emitter.. if you TRY to run 4 emitters DD from 3D.. you can expect to see the voltage start closer to 1.1V/cell average and get more like 45L/emitter = exactly the same output.. but for much less time.

you can also still use PQS not with the alignment marks and put three bare emitters on 120° apart...

It boils down to this.. alkaline do not have the POWER capability to run this much load.. NiMH not have a problem.. the trade-off is to use fewer emitters and maybe some resistance to keep the initial current below about 1.2A/emitter.

-awr

How did you measure the current? if you have all four wired up already you need to measure the current at the tailcap.. if you attempt to measure current as if you'd measure voltage.. what you are actually doing is shorting out the emitter through your ammeter and just pulling max current from the battery.

In-light current measurement:

remove tailcap
turn on light
set meter to DC A.. (10A).. make sure leads are in the correct jacks
touch Neg lead to bat - inside light
touch Pos lead to bottom edge of battery tube.

(press quick and hard.. if it's high-resistance it'll generate a lot of heat).

The batteries are all in series.. whatever current you pull from one it's from all of them... if.. you are measuring 2.3A from the battery.. you are only getting 2.3/4 = 575mA to each emitter.

looking at the C-size datashee from duracell.. we can find out a few things..

1) 150mohm resistance.. means that for every amp you lose 0.150V.. if you pulled 8A from a C size battery you'd get (1.5 - 8 x 0.150) = 0.3V remaining.. so you didn't pull that one off.

2) The only rate up to 2A rate.. but at 2A.. they show 0.3hours to 1.0V and 0.5hrs to 0.9V/cell.

So.. let's stay within the rated values as an example.. if you tune the thing 'til you get say 2.0A from the batteries and 500mA to each emitter.. the best you can expect is 30 minutes of sharply declining output.

Looking at the D size.. you'll get over 1 hour to 1.0V and more like 1.7hr to 0.9V/cell.. but that means.. with 3D.. the voltage will drop to 2.7V in about 90 minutes.. and the voltage will drop continuously from the start.

I built a light similar to this concept with 3 luxe's and tried to run it with 3D and they didn't have the voltage to get 700mA to each lux.. I re-worked it to use 4xC in a 3D host.. and now it will regulate (with fatman) 700mA with fresh batteries.. but the math works like this:

at 700mA it takes about 2.5W per emitter.. and that means 8.26W from the batteries.. at 1.5x3=4.5V that means 1.83A to pull that off.. bump that up to 4 emitters.. now you need 11W from the batteries and at 4.5V that means 2.44A from the batteries.. the problem is.. that's fresh batteries no load.. more realistic.. you'l get 1.25Vx3 = 3.75V fresh and 3.0V toward the end.. and that means starting current of 2.93 and ending current of 3.67 for 4 emitters.. and 2.2 to 2.75A with 3 emitters.. so.. with fresh 3D you can JUST regulate 700mA.

now.. using 4xC instead:

with 3 emitters.. the input current will range from 1.65 to 2.29A but with 4 emitters the input current will range from 2.24 (upper limit) to 3.11 (not doable).

Those are all values figured with fatman driver..

running unregulated.. you will not be getting nearly the output you deserve... i most certainly would not try to run more than 3 emitters.. the more current you try to pull from the bats.. the faster the votlage will drop and output will suffer a LOT.. You will likely get more light from 3D x 2 emitters than 3D x 4.

Get some accurate tailcap current numbers and wait for the current to 'settle in'.. the voltage on the bats will drop dramatically when you first turn it on.

Also.. measure the voltage at the emitters (all will be the same if parallel so just measure one)..

What is the Vf of the emitters again?

From my experience, the happiest solution you'll find will either be a 3 emitter fatman solution.. or a 3D x 2 emitter direct-drive solution. It does depend on the vF of the emitter.. but with 2 emitters.. DD from 3D.. vBat will range from about 3.75 down to 3.0.. and with Jbin emitter that would be a range of like 1A / emitter down to 122mA/emitter (with dead bats).

With 2 emitters.. you can use the PQS and have the alignment be symmetrical.. also.. you will push the emitters at 1A and get on the order of up to 90L/emitter.. if you TRY to run 4 emitters DD from 3D.. you can expect to see the voltage start closer to 1.1V/cell average and get more like 45L/emitter = exactly the same output.. but for much less time.

you can also still use PQS not with the alignment marks and put three bare emitters on 120° apart...

It boils down to this.. alkaline do not have the POWER capability to run this much load.. NiMH not have a problem.. the trade-off is to use fewer emitters and maybe some resistance to keep the initial current below about 1.2A/emitter.

-awr

The emitters have shown around a K Vf.

schiesz