Urgh...batteries suck

[bloodline]

I keep a glow stick in the fridge for use in an emergency.

Chemical light is the best!

[KennyR]

T_Bone wrote:
Flashlights suck, I use a propane lantern.

I had one, but threw it away. The mantles were too difficult to maintain. Besides, they can't throw a beam, and looking for the remote control down the couch is liable to be quite an experience with one.

[KennyR]

Seriously though, I'm thinking of just dumping alkaline and going for NiMH rechargables instead. Problem is, they have a lower voltage per battery (1.2 compared to 1.5). Well, thats not the big problem. The big problem is that packaging for every flashlight I ever bought screams: "Only use alkaline batteries in this product!" They don't recommend it, they demand it. Anyone know why?

[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.

[KennyR]

Karlos wrote:
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.

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

NiMH also has a nice flat output, and can punt out just as much current until its drained. It doesn't tail off, so no yellowing of bulb light (not that I get any anyway, my flashlights are all LEDs). That in itself presents a problem: the current drain from LEDs is so low that its really not much more than just leaving the batteries inside and not turning it on! I'm not sure NiMH likes that kind of job. In fact I'm pretty sure it doesn't.

I could recharge NiMH every 30 days so I'd never have problems. At this rate, I'll be replacing alkaline every 40 without ever using the damn things!

[T_Bone]

KennyR wrote:

T_Bone wrote:
Flashlights suck, I use a propane lantern.

I had one, but threw it away. The mantles were too difficult to maintain. Besides, they can't throw a beam, and looking for the remote control down the couch is liable to be quite an experience with one.

Remote control? Do you have a battery powered TV, or just no living room lamps? :-)

[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 ;-)

[blobrana]

Hum,
what is flat output?

A steady flow of electrons, er, as opposed to wave-like output?

BTW, has anyone actually made a battery here?

[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 ...

[blobrana]

Hum,
So kenny could have all the bits he needs to make a battery in a kitchen cupboard....pre-prepared in advance so he just need to `insert the cathode` type thing for it to work...

i found this handy table for him to experiment with

-------------------------
So is that, what a flat output is?

[odin]

Uhm, all one needs to make a battery is an orange and a zinc and copper plate from what I remember.

For a school project we once considered a bunch of spuds in serial. But that couldn't deliver enough current ;-).

[KennyR]

Ok, done some research into NiMH batteries, and I'll think I'll do the switch. They may only be 1.2V compared to alkaline 1.5V, but apparently alkaline lose EMF quite quickly and they average at 1.2. NiMH give a much more even discharge, which is useful since the flashlights don't have current regulators and go dimmer as alkaline drain.

And most of all I don't need to keep replacing them. If I charge them every two weeks I won't have to worry about leakage or hydrogen gas buildup. No arguing with the energy density though - alkaline still kick NiMH ass, so I wont get my 900 hours of light. Pity but not the end of the world, unless it really does come to the end of the world. In which case I'll loot a shop and get alkalines.

Ladies and gentlemen, you may keep your primitive combustion products and homemade voltaic piles. I'm going rechargeable.

[gizz72]

Greetings,

@KennyR

:idea: Why not change the flashlight bulb to something efficient to say, small but powerful LED, like what most mobilphones have, only brighter, and something very reflective on it's side for best illumination.
Very little power needed and smaller in size. Man, you can even use a AAA battery. What do you think?

Regards,

Gizz

[KennyR]

gizz72 wrote:
Why not change the flashlight bulb to something efficient to say, small but powerful LED

None of my flashlights actually have bulbs. They're all LEDs. But actually providing light isn't the reason I keep running out of batteries, it's the drain the flashlights have when not on that's freaking me out.

[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...

[KennyR]

@Karlos

They are white (although they look slightly bluish), and they are brighter than most ordinary flashlight bulbs. A Lightwave 4000 (with 10 white LEDs) which is advertised to run with 900+ hours on 3 D batteries, and a Lightwave 2000 (4 white LEDs), advertised for 340 hours on 3 AA. Actually they'll probably still be bright enough to read by long after that. So they ain't high current! ;-) (The LW4000 is probably the world's most efficient flashlight, and I had to ebay for it and get it stateside.) Oh, and my kinetic, with its purple LED that seems to be lit no matter how long the thing is left on. But isn't very bright.

LEDs rule, but they have one important failing: they don't throw a beam. Further than 10m, they're useless. Thats why some manufacturers are making hybrids with both xenon/halogen bulbs and LEDs. LEDs for ultimate battery economy, bulbs for long distance.

It seems even the world's most efficient flashlight still suffers from parasitic drain.