One battery or two ?

I am curious to find out ,going by numerous posts I've read that some lasers given enough space can put in two 16340s and get nearly double the power output for half the time rather than one 18650. Its implied on some posts its only the space you have that stops you from putting in 2 16340s as they will be longer but not by that much. .I cant see how you can just double the voltage with no other modification. If there is a modification in basic terms what is it. Or are all the lasers that do this have a special driver board as a replacement part to enable it to cope with twice the voltage without killing the diode

The diode pulls the voltage it needs from the battery via the driver modulation.
Most drivers aren't engineered for such a variation , thus it is CRUCIAL to ask the manufacturer about the specs before doing so.

For example , while Survival Laser's driver can cope with both 2 RC123A cells or 1 18650 cell.
CNI's lasers are specifically engineered for ONE 18650 cell.

OK that's half way there, of course a lot of lasers are brand x and as to the manufacturer that's a company in China so no idea I'm obviously not going to put in two batteries and just try it any other clues i have lasers that have an extension tube is this a clue at all to two batteries at all, especially when standard its the 16340 battery

Blaster said:

OK that's half way there, of course a lot of lasers are brand x and as to the manufacturer that's a company in China so no idea I'm obviously not going to put in two batteries and just try it any other clues i have lasers that have an extension tube is this a clue at all to two batteries at all, especially when standard its the 16340 battery

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Ah.. So you are asking about the technical bit that allow drivers to pull the voltage as needed?
Well.. Why not shoot DTR or Garoq a message?
I'm sure asking the engineers would be a lot more direct

Yeah would be a better idea, i assumed the extension tube is to put the higher capacity 18650 battery instead of the 16340 but it may be to run both in series double voltage,i have a 7 led Cree XML T6 torch that has the extension tube and you can run that torch with two or three batteries you are obviously putting more volts in not extra battery life as its in series not like the sky king torches that run 4 18650 in parallel that's partly what got me asking the question

The extension tube is usually to be able to use two 18650 instead of two 16340 so you can get better battery life. All the drivers will operate within a certain voltage range. Some are designed to use one battery but most require two.

I am starting to lose you here... so.... what do you want to know specifically??

Blaster said:

I am curious to find out ,going by numerous posts I've read that some lasers given enough space can put in two 16340s and get nearly double the power output for half the time rather than one 18650. Its implied on some posts its only the space you have that stops you from putting in 2 16340s as they will be longer but not by that much. .I cant see how you can just double the voltage with no other modification. If there is a modification in basic terms what is it. Or are all the lasers that do this have a special driver board as a replacement part to enable it to cope with twice the voltage without killing the diode

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Yea this is not right. You unit will either take one or two Li-Ions depending on what kind of driver it is using and it is not double the batteries double your fun. Using 1 cell in a unit that calls for two cells will just make it fall out of regulation and not light up or not be very bright. Using two cells in a unit that calls for just one most likely will leave you with a dead driver and diode making your unit a paperweight.:cryyy:

DTR said:

Yea this is not right. You unit will either take one or two Li-Ions depending on what kind of driver it is using and it is not double the batteries double your fun. Using 1 cell in a unit that calls for two cells will just make it fall out of regulation and not light up or not be very bright. Using two cells in a unit that calls for just one most likely will leave you with a dead driver and diode making your unit a paperweight.:cryyy:

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not very bright?

Now thats weird , I thought LED won't light up at all if its below the required voltage and current

EpicHam said:

I am starting to lose you here... so.... what do you want to know specifically??

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IS there any way of knowing other than manufacturer specs whether you can add the second battery like the survival ones you mentioned and get more power rather than again as mentioned above just burn out the diode and end up with a paperweight :thanks:

Blaster said:

IS there any way of knowing other than manufacturer specs whether you can add the second battery like the survival ones you mentioned and get more power rather than again as mentioned above just burn out the diode and end up with a paperweight :thanks:

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Go send the manufacturer an email?

there are different types of drivers; buck, boost, linear, etc..... To put is simply, a buck driver reduces the voltage, boost driver boost the voltage and linear keeps it as is. You can read more in depth about driver types here: http://laserpointerforums.com/f67/how-laser-diode-drivers-work-explanatory-thread-71513.html

Blaster said:

IS there any way of knowing other than manufacturer specs whether you can add the second battery like the survival ones you mentioned and get more power rather than again as mentioned above just burn out the diode and end up with a paperweight :thanks:

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It doesn't work that way, the laser diode drivers are constant current drivers, more voltage doesn't mean more power, its the current the driver is set at that decides the power. For example you have a M140 driven at 1.5A, you could replace the driver with one that is 1.8A and get more power or with one that is 1.25A and make it less powerful. Weather it requires one battery or two depends on the driver itself.

If its a buck, putting the double voltage will draw half the current of one cell (ideally).
IE if your laser (driver) draws 1A when fed 4.2V, in perfect conditions, it would draw 500mA from 8.4V.

Its all about power. The driver will draw much current needed @ the battery voltage, to suffice the diode current you set...
BUT the driver should have the capabilities to accept a input that high..

Lets hope this help you understanding
I measured something similar some time ago;
I set a Flexdrive to source 4.8W of power to a 445nm diode. Don't remember exact voltages/currents, but it were 4.8W in the diode.

And I started measuring the battery out current:
@ 4.2V, it outputs 1.28A, giving 5.37W IN, thats 88.2% efficiency.
@ 3.7V, it outputs 1.65A, giving 6.1W IN, thats 73% efficiency.
@ 3.3V, it outputs 2A, giving 6.6W IN, thats 62% efficiency.
@ 2.92V, it outputs 2.01A, giving 5.86W IN, thats 78% (?) efficiency.

- During all tests, the diode power IN were 4.8W.
- I used a bench supply where I do study. Remember there are no LPM readings, all power measurements are electrical power.
- These tests were made for a battery lifetime study of mine, so don't assume 100% accuracy on it.
- It were done in a electrical engineering school, so their multimeters should be accurate... maybe not.
- I remember playing with higher voltages, and the Flex got a peak efficiency @ around 5 or 5.5V. I can't remember. Will test again.

Blaster said:

I've read that some lasers given enough space can put in two 16340s and get nearly double the power output for half the time rather than one 18650. Its implied on some posts its only the space you have that stops you from putting in 2 16340s as they will be longer but not by that much. .I cant see how you can just double the voltage with no other modification.

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First of all, two 16340 cells store less power than a name-brand #18650.

Looking at the most popular 16340 cells, they are 880 mah.

The Panasonic 18650 cell has 3400 mah or or 386 % more current capability.

This means the 18650 cell will have much more power, enabling longer run times before the laser diode dims.

Some electronic drivers can utilize the extra voltage, and provide more current,

but there are some drawbacks.

The more popular linear drivers will usually overheat from dissipation of the extra voltage.

Reliability at higher voltage will also be lessened.

Regardless, the power will decline quickly since the 16340 cells have higher internal resistance.

LarryDFW

OK well like no name brand there no way to know but thx for the answers. I would be nice to just be able if you have the room put in a second battery and get more power output