3.2v vs. 3.7v 16340

[Nooblaserdude]

I just got the 1 watt version of this laser in the mail and it says to use 16340 batteries. What I'm wondering is, does it matter if I use 3.2 volt batteries or do I need to use 3.7? I have a seemingly unlimited supply of 3.2v batteries from where I work and it would be nice if I could use those. But I don't want to ruin the laser and will get 3.7 volt batteries if I need to. Also, if I do need 3.7 batteries then don't be afraid to point me towards a reputable supplier. Thanks in advance.

 

[Deleted member 42751]

3.2V batteries are typically of LiFePo4 chemistry, which means they have lower capacity than typical Li-ions. They should work with most 532nm greens, but other wavelengths might not like the low voltage. You won't kill them either way, typically overvolt is what kills lasers, not undervolt.

 

[Cyparagon]

It won't hurt for sure. Whether it works at full power with a violet depends on how the boost driver is designed. It will probably be fine.

 

[Seoul_lasers]

3.2V batteries are typically of LiFePo4 chemistry, which means they have lower capacity than typical Li-ions. They should work with most 532nm greens, but other wavelengths might not like the low voltage. You won't kill them either way, typically over volt is what kills lasers, not undervolt.

Precisely correct. LiFePo4 cells have lower working voltage than Li-ion and li-poly cells.

On the boost driver issue,
I do know however from experience that my boost driver in my ~700mW 12x 405nm build from member Danguin did NOT seem to appreciate the lower voltage from an A123 branded LiFePO4 18650 sized cell. :undecided: The laser would powerup, and then immediately start rapidly flickering. This went away as soon as I put in a fresh Li-ion (18650) cell.

Perhaps newer boost drivers are more compatible with LiFePO4 cells?
That's a good question to ask really as LiFePO4 batteries become more and more commonplace.
:thinking:

Anyone else have LiFePO4 experiences on boost drivers?

 

[Astralist]

Depending on the boost drivers configuration or the IC used, using 3.2v LiFePO4 might give you an "unfinished boost cycle" (idk the words in English)
Additionally with its low voltage, the drivers needs to draw more current which might be a problem if there is a mismatch on the component rating calculation from when its designed.
And the real problem is that you need to take account the minimum input of the IC used in those boost drivers.

 

[Seoul_lasers]

Depending on the boost drivers configuration or the IC used, using 3.2v LiFePO4 might give you an "unfinished boost cycle" (idk the words in English)
Additionally with its low voltage, the drivers needs to draw more current which might be a problem if there is a mismatch on the component rating calculation from when its designed.
And the real problem is that you need to take account the minimum input of the IC used in those boost drivers.

That's basically what I was under the impression about. The IC may not be able to boost properly (voltage too low hence incomplete boost cycle) instead causing the driver to instead pulse rapidly which is what I was seeing.

Having a look at boost ICs, many on the market now that are able to use LiFePO4 chemistry, but ICs from just a few years ago were largely meant specifically for Li-poly or Li-ion.
They have a minimum cutoff at ~3.5v. LiFePO4 boost seem to go down to ~2.5v as far as I am reading in data sheets.

 

[Benm]

With a boost driver it's not only the IC that has to cope, but the inductor as well.

If the inductor is designed to be physically small it can be under spec to boost from a lower voltage, even if the driver chip has no probem with that voltage per se.

With a fixed frequency driver you'd get to a point of magnetic saturation of the inductor, causing a big loss of efficiency and a driver just unable to supply the set current.

This is not typically dangerous for your laser though. It may run at lower power, it may flicker, but if the driver design is half decent it will not run your laser (diode) at higher power/current then intended.

This is all presuming the driver actually is a boost driver, which it may not be.

When using 2 cells in series their output voltage would often be higher (6 to 7.4 volts) that what the diode actually needs (5.5 to 6 volts), and a buck or low-drop linear driver may work better. Make sure what kind of driver is in your laser!

With blue or violet lasers running from a single cell you can be confident it is a boost driver, but with 2 cells it could as well be buck or linear really.

These SOKY sellers don't seem that tech savvy at all - they specify a duty cycle of 10 minutes on and then 10 seconds off for the 1 watt model. They should realize that this is nonsense, it's only 1.5 percent lower than continous operation, and anyone that ever did any electronics design would have turned down the power by 2 percent just to guarantee you can leave it running continously at that point.

I don't think much work as gone into their maths though, the 2 watt model can be ran at 3 minutes on and 20 seconds off - effectively 90% duty cycle - according to their specs. Since it's exactly the same case i'd call BS here: either you can run all of them continously or all of them will overheat if you try. Considering the size of the things i hope the first one is true, but i will not make any guarantees to that