The small button batteries under the load of the laser diode, are most
likely having a greater voltage drop, than the higher capacity C batteries.
The small button batteries, cannot have the capacity of the C batteries.
The breakover voltage where any LED device (laser diode) will function is
very tight. A small difference of the supply voltage in this region will
normally make a large difference in the output of the LED. Take care to not
exceed any LED's maximum voltage rating. They can be easily damaged.
--
Greetings,
Jerry Greenberg GLG Technologies GLG
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"One Two" wrote in message
om...
For fun, I am increasing the life of little laser pointers for cats.
I noticed that 3 button batteries, (either alkaline or silver-oxide,
357, or zinc-air hearing aid, 675) which produce 3x1.5 3x1.55 3x1.4
volts respectively, are not nearly as bright as 2 x C cells producing
only 2x1.6 volts initially.
Why is this?
The 3 button batteries are all over 4 volts although their capacities
are around 105 165 540 mAH respectively.
The C batteries are a little over 3 volts for 2 of them but their mAH
are quite high relatively, 8350 mAH. Alkaline batteries for the C.
There are discharge characteristics of batteries that I am woefully
ignorant of, well, maybe not woefully. Got me curious.
For a little test, I noticed that 2 C cells enable the laser pointer
to draw 25 mA but 3 C cell will draw 27 mA. For those 2 extra mA
coming from using 4.5 volts instead of 3 volts (nominally), the laser
is noticeably brighter. I assume the nM of the laser is possibly being
changed or just the power throughput or both. I read that as the laser
drops from 660-670 nM to 650 nM the light gets brighter.
My long-winded question is that I thought a device draws only the
current it needs. But if there is more reserve capacity as with the C
over the button batteries, the device draws more current or the
batteries allow more current to be drawn or what?
Wuold the true be same for D batteries over C also?
I noticed that the lumens stay the same with Maglites using C or D
batteries but the PBC or goes up slightly using D over C batteries.
So again, bigger batteries allow more current to be used or what?
Thanks for any input into this burning question. I cross-posted this
since it's hard for me to post and this is the sort of question that
can be answered by those who either tinker or design or repair.