Urgh...batteries suck

[Karlos]

KennyR wrote:

Squatting at the window in the dark frenetically pumping some small rod-shaped object is liable to attract attention too, I suppose.

:roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao:

[Karlos]

Alkaline batteries have higher current densities and are less likely to leak than other disposable batteries. They probably don't suggest rechargables because they don't output the power and hence results in a lower brightness. Also, rechargable batteries (lead acid excluded of course!) generally don't cope with higher current demands well (OK, these things are relative, but a normal bulb drains a lot more juice than most battery driven components), so you get a dull beam that doesn't last too long - not exactly what they are trying to sell.

There is no technical reason not to use non-alkaline batteries I can think of.

[Karlos]

KennyR wrote:
You're right apart from the current demands; NiMH is better under high drain than alkaline. But not the kind that flashlights will give.

Well, that's kind of what I was hinting at. Didn't realise NiMH was flat output. Thats interesting - the internal chemistry must be quite funky ;-)

[Karlos]

blobrana wrote:

BTW, has anyone actually made a battery here?

Sure. I made some interesting cells when I was mucking about in labs. Tried to see how far apart in the electrochemical series I could get to get a large EMF...

Never could find an ionizing solvent sodium wouldn't simply reduce. Apart from liquid ammonia, but then it just dissolves in that ;-) Pretty colour though ...

[Karlos]

@Kenny

What sort of LEDs are they?

It's not necessarily good, but ultra bright red (>15,000 mcd) draw a tiny current (20mA or so). Ultra bright green types draw a bit more current (but not much more), and green is perceptably much brighter than red to the normal human eye.

"White" LED's AFAIK draw considerably higher currents at the same luminous intensity...

[Karlos]

@Kenny

Yeah I know that they aren't current hogs compared to conventional bulbs :-) However a superbright red LED (harder to see though) would probably give twice the battery length. A  green version would look far brighter to the human eye and still last maybe 60% longer than white LEDs.

Still, try selling a green torch :-D

[Karlos]

bloodline wrote:

The potassium hydroxide disolved most things, including the araldite, the perspex and the skin on my hands.

What, boiling 8M KOH attacked the stuff? Now there's a surprise :-P

You should have used a pure petroleum wax coating inside the case, obviously choosing one with a melting point higher than your operating temperature. KOH wouldn't have eaten it...

-edit-

Assuming it was aqueous KOH and not alcoholic, of course ;-)

[Karlos]

Colour blindness has nothing to do with green receptivity. It so happens the monochrome cells that make up the majority of the retina respond to light in the green/yellow region of the spectrum. Those cells aren't used to judge colour, only brightness, hence we see green as brighter than other shades regardless of wether or not we percieve the colour itself.

-edit-

Given the spectral class of our sun (G2/Yellow), this makes perfect sense - we'd be hopeless if we depended on eg far red for our overall brightness information :-)

-/edit-

Trust me, I'm extreme red-green colourblind ;-)

[Karlos]

@Kenny

I meant that green would appear brighter than red (thinking along the single wavelength LED approach) :-D

Naturally white would appear brighter still since it is the sum of all wavelegths...

[Karlos]

@blob

I'm sure I said yellow/green in that last post ;-)

@bloodline

Maybe she meant Quantum Mechanics, in which case she's spot on ;-)