Krill electronic glow sticks
(from smallest to biggest!)
Review date: 3 October 2007
Last modified
03-Dec-2011.
Electronic glow sticks are peculiar things. They are what they sound like - glow sticks that look more or less like the chemical kind ("chem-lights", if you want to sound like G.I. Joe), but they run from batteries, and so can be turned on and off at will.
The only way to "turn off" a chemical glow stick is by freezing it to slow down the reaction, and even that doesn't stop the reaction completely. Actually, even high-quality chemical glow sticks are likely to go bad after a few years on the shelf, whether you use them or not. Practically, the only way to turn a chem-light off is by sliding an opaque sleeve over it, which is how people do it when leaving the light on may attract gunfire.
On the other hand, chem-lights are very inexpensive and very tough - even if you cut one open, the liquid inside will keep glowing.
No electronic alternative can be anything like as cheap, or as tolerant of abuse.
The big fish in the small electronic-glow-stick pond is Kriana Corporation, whose "Krill" sticks create a very chemical-glow-stick-ish light. They use electroluminescent, or "EL", material, curled up in a cylinder and sealed inside a very tough polycarbonate tube. Batteries go in the middle of the tube, and an O-ring-sealed screw-on cap serves as an on/off switch.
The result is almost the same 360-degree light as a chemical glowstick. There's a thin dark seam down one side of each Krill stick, but it's not wide enough to matter. You can also get "180 degree" Krill sticks that only glow on one side, and give you twice as much battery life; on top of that, there are flashing sticks for marker-light duty whose batteries last even longer.
I checked out a few Krill sticks years ago in this review, but they've got some new models now.
On the left, one of the two-AA-battery sticks from that old review. On the right, the newer, sleeker two-AAA-cell model.
In the middle, something Kriana call the Krill Light Torch.
The Torch accepts a magnificent six AA batteries. And, with a total height of more than 34cm (13.4 inches) and a light-emitting length of about 25cm (9.8 inches), it's got about 3.2 times the radiating area of the AA-size sticks.
(The product page for the Torch currently confusingly states that it has "22 inches of light emitting material"; I presume they mean 22 square inches.)
All of these sticks are yellow when off and a bluish-green when on. That's the native colour of the electroluminescent material, and therefore the brightest.
Kriana just call this colour "green", and they make Krill sticks with various other colours - blue, white, orange, red and yellow. And some more expensive infrared models, whose output is only visible through something that can see near-infrared, like a night viewer or unfiltered CMOS or CCD sensor.
All of the Krill sticks except the green one still use this same yellow-green EL material, though; the other colours just hide it under a phosphor coating that converts the light to a different colour. The coating is far from 100% efficient, so the other colours are all significantly dimmer than the green ones.
(Human vision is also more sensitive to green light than to any other colour, which makes the green Krill sticks look even brighter.)
All three Krill sticks have the same simple switch, which they share with many other waterproof flashlighty things. The O-ring-sealed battery compartment cover screws on, and when you screw it all the way down the spring in the base makes contact with a thin wire leading to the other end of the stick, and the light turns on.
The switch-cap for the two smaller sticks is on the bottom, but the Torch's switch-cap is on the top; it's got a fixed base-cap with a bit of weight in it to encourage the Torch to stand upright.
This may have something to do with the fact that the Torch doesn't have an official waterproof-ness rating. The smaller sticks are all rated as waterproof to 150 feet, and the Torch is still definitely rainproof, but you're apparently on your own if you decide to take it diving.
Despite the weighted base, the Torch still only weighs about 240 grams (8.5 ounces) with batteries. Note that the standard rectangular spring-top alkaline six-volt battery that many electric camping lanterns use weighs something like 885 grams all by itself, before you even put it in a lantern. So the Torch may be the biggest Krill stick, but it's still nothing like as heavy and bulky as an ordinary lantern.
(The lantern battery also, mind you, has a nominal capacity of more than 150 watt-hours. Six AA alkalines only have a capacity of about 25 watt-hours.)
If you're climbing a mountain or being shot into space then the extra bulk and weight of the Torch may still rule it out. But it only costs $US59.95, only slightly more than twice as much as the smaller sticks. And because it's so skinny, it's easier to pack than you might think. Just put everything else into your luggage, then stab the Torch into a gap somewhere. Sorted.
The AA stick is 2.75oz (78 grams) with batteries, and the little AAA stick is only 1.25 ounces (35.4 grams). The AAA sticks all cost $US24.95 plus shipping direct from Kriana; the various models of AA stick vary in price from $US24.95 for the 180 degree Original model, though $US29.95 for the 360 degree high-brightness "Extreme", to $US34.95 for the infrared versions, for people who want to make sure their fellow elves and/or Predators can see them.
Brightness
Chemical glowsticks aren't very bright, and neither are the Krill versions. If you want maximum illumination power, you want a normal flashlight or camping lantern or something.
But this doesn't mean the Krill sticks are only useful for location marking. Even my old dim AA stick - an "Original" model, as opposed to the much brighter "Extreme" version - is a heck of a lot better than nothing if you need to find your way in the dark. Its light output is similar to that of the backlight on many small mobile phones, and heaven knows enough people have used those as flashlights in a pinch.
The approximate illumination threshold for human colour vision - which doesn't really matter when your light source only has one colour in it, but stay with me here - is about one lux. The minimum illumination level for any kind of useful vision at all, for normal adult humans whose eyes have adjusted to the dark, is about 0.1 lux. You'll probably still be able to grope your way around with less than 0.1 lux - if you've got decent night vision, even the 0.001 lux of a clear moonless night is better than nothing - but 0.1 lux is a pretty good place to put the line below which you'll start using touch as much as vision.
I own a light meter, but it's a pain to use at these very low levels - I keep getting results that violate the inverse-square law. So the one-lux illumination level for the old AA stick seems to be lurking somewhere around the 10 to 15 centimetre mark, but I wouldn't bet my life on it.
Even this dim Krill stick should be able to light a one-man tent well enough for you to see where your stuff is, though. And it's not bright enough that people for miles around will be able to see your glowing tent.
The AAA stick is of the brighter "Extreme" type, though it doesn't say it on the product page. Kriana figured that most AAA and Light Torch buyers wouldn't be interested in the dimmer versions, so every AAA stick and Torch has "Extreme"-level output.
I presume the AAA stick therefore has not much less output than a green "Extreme" AA stick. I found its one-lux threshold was somewhere around 20cm.
The one-lux threshold for the mighty Torch was around a metre away from it.
In practical terms, this means that the Torch can light a whole room...
...brightly enough for you to see what you're doing quite well. The Torch still isn't as bright as a basic camping lantern, though, and its monochromatic light makes it impossible to see colours.
Throwing the troublesome light meter aside, I tried a more practical test: How far away from each stick can you be, with dark-adapted eyes, and still get enough light to read a book reasonably comfortably?
For the old low-brightness AA stick, this distance was tiny. Maybe six inches. So you pretty much need the glow stick to be somewhere between your face and the book, which isn't very practical even if you've got one of the 180-degree versions that won't throw light back toward your face as well as toward the book.
(That sort of light appears to be standard issue in TV science fiction, where all space suits have lights inside the helmet that make the actor's face clearly visible. In the real world, the glare from the face lights would prevent you from seeing out.)
The AAA stick extended this distance to about a foot, making it just about practical to stand the stick next to your head while you lie down in your tent and read a book in a fairly normal way.
The Torch, of course, did much better. Its comfortable reading distance is more like three feet. A Torch really will make a quite practical light for a whole multi-person tent, provided you don't need to see colour.
This last part can be quite important at times. It's hard to read a map, for instance, in monochromatic light.
The abovementioned inverse-square law means that you have to move about 3.16 times as far away to reduce one-lux illumination to 0.1 lux. If you're getting one lux at one metre, you'll get 0.1 lux at 3.16 metres (and 0.01 lux at 10 metres, 3.16 squared). I'm loath to put definite figures on the distance thresholds for 0.1 lux illumination for these three sticks, though, because multiplying the already-fuzzy numbers by 3.16 isn't going to give a more accurate result.
Power
Because my old AA stick is the not-very-bright "Original" type, it draws little power from its batteries. The "Extreme" versions are the ones you should choose if you actually want to light an area, rather than just use the stick as a marker light - which is why all AAA sticks and Torches are of this brighter type - but you pay the price in battery life.
Through the extra load of my multimeter, the AAA stick I got for review consumed about 50 milliamps from fresh batteries. Kriana quote the run time of the AAA stick as "up to 25 hours", which these numbers support, for alkaline batteries at least.
I found the AAA stick's threshold for reasonable brightness was actually about 1.8 volts, at which it was still drawing about 35 milliamps. Below that voltage, both current draw and brightness dropped precipitously.
1.8 volts from two AAAs is 0.9 volts per cell, at which point alkaline AAAs are likely to have a little more capacity left - but that capacity won't last long at 35mA. The more heavily you load ordinary alkaline batteries, the less capacity you get. (Cheap carbon-zinc "super heavy duty" batteries are even worse.)
Taking this all into account, I reckon fresh brand-name AAA alkalines may be able to run the AAA stick at decent brightness for as much as 30 hours. If you're stuck in the boondocks and can only get carbon-zinc batteries, you'll probably find that their lower tolerance for anything but very light loads means they last less than ten hours.
My old "Original", non-"Extreme", AA Krill stick doesn't have the same sharp 0.9-volt-per-cell threshold. It just dims steadily as the input voltage drops, with current dropping along with the brightness. The old AA stick still lights up noticeably, but probably not brightly enough to be useful for anything, at only one volt.
This makes the "up to 120 hours" battery life Kriana quote for the Original sticks actually quite conservative. The Original stick draws about 20 milliamps from fresh batteries, but modern brand-name alkalines can deliver something like 2800 milliamp-hours of capacity at that low drain level. Even if the AA stick's draw didn't fall as the batteries drained, it'd still give you an easy 140 hours of run time.
For marker-light duty, I bet the AA stick would be fine after three hundred hours, if you fed it modern alkalines.
The Torch needs a lot more power than the smaller sticks, as you'd expect. Its through-multimeter current consumption was 0.19 amps from fresh alkalines - and that's six fresh alkalines, delivering a nominal nine volts.
So the AAA stick is about a 150 milliwatt device, the old dimmer AA stick is only about a 60 milliwatt proposition, but the Torch is more like 1.7 watts. That's nothing special by flashlight standards, but it's quite a lot for an electroluminescent device.
I found the Torch's threshold for brightness good enough to illuminate anything at all was around 6.2V, where it was still drawing about 100mA. That means it'd drop though that brightness level quite quickly; 100mA is a pretty serious load for alkalines that're already down to about one volt per cell.
The threshold for brightness I could mistake for full brightness, though, was up around 8.4 volts, at which the Torch's voltage regulating hardware was already drawing 190mA again.
Kriana quote the Torch's run time at "over 10 hours", which is I think pretty much on the ball, if you're using fresh modern alkalines. If it drew 190 milliamps constantly then it'd beat its alkalines to death in only about four hours - because higher load means less effective capacity - but its draw falls over time, which saves the batteries.
Fresh alkalines will probably take about an hour to be sucked down to the 1.4 volts per cell that adds up to 8.4V, the point at which the Torch starts clearly dimming, and drawing less current.
If money is no object, you could run any of the Krill sticks from non-rechargeable lithium batteries. Lithium AAs have been around for many years, and lithium AAAs debuted a few years ago. They can even be had in cheap no-brand versions on eBay.
Lithium AA and AAA cells don't actually have much more capacity than alkalines, for relatively-low-power applications like the AA and AAA Krill sticks. Their advantages are lower weight (an alkaline AA is about 23 grams; a lithium AA is less than 15g), very long shelf life (after 15 years their capacity's only down by 10%), and operation at very low temperatures.
That last part could be particularly handy if you intend to use a Krill light in extreme conditions. Alkaline batteries have a water-based electrolyte that's no good much below zero Celsius, but lithiums are A-OK down to minus 40, that magic point where the Fahrenheit and Celsius scales cross over and the mercury in your thermometer freezes.
In normal use, lithium AAAs may make the smallest Krill stick run acceptably for 35 hours versus the 30-hour limit for fresh alkalines, but that's about it. They'll do about the same - which is to say, close to nothing - for the AA sticks, even the "Extreme" versions.
The Torch, however, draws enough current that it ought to run noticeably brighter for longer if you feed it lithium AAs. Lithium AAs actually deliver about 1.7 volts per cell when they're fresh (making them a bad idea for powering incandescent flashlights bulbs, which run very bright... for a little while...). So six of them give you an initial nominal 10.2V.
At that voltage, the Torch's control hardware draws only slightly more current than it does at 9V - about 205mA, according to my bench power supply, which I connected to the unlikely-looking test hardware I used to get a probe down to the bottom of the Torch's lengthy tube.
That's good. If a device's current draw increases with increasing voltage as if it were a simple resistive load, which is the case with flashlight bulbs, then it's probably a bad idea to run it from much more than its stock voltage.
The Torch seems happy enough at ten volts, though, and I reckon it'd give you a solid twelve hours of run time from lithium AAs.
Lithium cells have a flatter discharge curve than alkalines, too. With a moderate load, they stay above 1.4 volts per cell for most of their capacity. So I wouldn't be surprised if a Torch running from lithiums gave you something close to full brightness for ten of those twelve hours, versus maybe five out of ten hours for alkalines.
(If you're looking for full specifications for a bunch of different battery types, check out Energizer's data archive.)
Nickel-cadmium and nickel-metal-hydride rechargeable batteries were not, until recently, a good idea for most people's portable lighting applications.
Rechargeables are much happier delivering high currents than any non-rechargeable cell the same size. But ordinary NiMH and NiCd cells have high "self discharge" - they go flat on the shelf, all by themselves, quite quickly. If anything, the self-discharge problem was getting worse as higher and higher capacity NiMH cells hit the market. Freshly charged super-high-capacity brand-name NiMH cells may dump half of their charge in six weeks, and be essentially flat after only a few months. That's probably not a characteristic you're looking for in a flashlight battery.
Recently, however, there's been a wave of low-self-discharge NiMH cells, often sold as "pre-charged" or "ready to use", because they can indeed be charged at the factory and still have most of that charge even if they've been sitting on the shelf for a year or more.
The first low self-discharge cells were Sanyo's "Eneloop" cells, but there are many other options now. Low self-discharge cells have lower capacity and cost more, but the "GP ReCyko" AAA cells I've bought still have 820mA nominal capacity, which means they ought to last at least three quarters as long as alkalines in the AAA Krill stick.
GP ReCyko AA cells are currently rated at 2050mAh, again about three-quarters of alkaline capacity for small loads, so they'd be a perfectly OK option for the two-AA Krill sticks too.
The nominal voltage for NiCd and NiMH rechargeables is only 1.2 volts per cell, though. This is OK for the smaller Krill sticks, which give something not very far from their full brightness from 2.4 volts. But the Torch is quite dim at only 7.2 volts (6 times 1.2). It's still drawing 150mA, and much brighter than the smaller sticks, but it's only about two-thirds as bright as it would be from six fresh alkalines.
That's not terrible, but I still can't really recommend rechargeables for the Torch. If you intend to use your Torch a lot, I suggest you buy a bulk pack of cheap off-brand alkaline AAs.
There's one other problem with NiMH and NiCd rechargeable cells, which will probably never be solved. That problem is that they have a very flat discharge curve - even with quite a high load, they stay close to their nominal voltage for almost the entire discharge cycle, then plunge rapidly to zero.
This is a desirable feature for many purposes, but for portable lighting it gives you little warning that your batteries are going flat. One minute your flashlight's fine, the next it's useless.
People aren't likely to be using any Krill product as their sole illumination device, though. So, for these lights, this shouldn't be a problem at all.
The high power of the Torch, by the way, makes it the only Krill light that you can clearly hear operating.
Electroluminescent material runs at low current from a relatively high AC voltage - 80 to 150 volts. To get that from low voltage batteries, you use a little inverter circuit, which will hum or whine at its switching frequency.
The inverters in the smaller sticks are just barely audible if you actually put the top of the stick in your ear. But the bottom of the Torch, where its electronics are, sounds quite like a mosquito when the light is running. It's also only about as loud as a mosquito, though, so it's unlikely to annoy you if it isn't standing right next to your head.
Overall
If you're in a situation where you want to see stuff near you, or be seen by someone else, but not be seen by everybody in the area, then a switchable glowstick is a great product.
The Krill sticks are also handy if you want to preserve your night vision but also need a bit of light for a moment to see where you put that bat microphone/telescope accessory/triple-shotgun, or just want to spice up your ground-crew boogie.
If you want a general purpose lantern, a Krill light is not for you. Electroluminescent material just isn't terribly good at turning electrons into photons, compared with mainstream technologies like fluorescent tubes or white LEDs.
If you need disposability in your glow sticks, the Krill lights are also unsuitable - well, unless you're really rich.
For many other glow-stick applications, though, these things are likely to be a more elegant solution than chemical sticks. Just the ability to turn them on and off is a huge selling point, even if you don't often find yourself being firmly instructed to put that bloody light out lest someone try to kill you.
The Krill lights are likely to last a very long time. Electroluminescent material doesn't burn out like a light bulb, but it does slowly wear out; Kriana quote the lifespan of the AA and AAA sticks as "over 3000 hours" (the "Original" models will probably last longer) and the Torch, which pushes its EL material a bit harder, as "over 2500". All of them ought to still work even after that much time (104 to 125 straight days of on-time); they'll just be quite a bit dimmer than they were to start with.
Even if the Torch went pop and died after exactly 2500 hours, though, it'd still have only cost you about 2.4 cents per hour plus the (much larger) price of batteries. I can live with that.
The AAA stick is very slim and compact; you can easily carry it in a pants pocket and forget it's there. The AA sticks come in numerous flavours and have much better run time.
And the Torch is a truly unique product.
It's not the biggest glowstick in the world - I think the longest standard chemical glowstick size, not counting the skinny "necklace" types, is 15 inches, versus the ten luminous inches of the Torch. But the Torch is still an effective, lightweight and frankly just plain cool small-area light, and it doesn't cost very much - sixty US bucks plus delivery is OK with me.
I defy anyone to resist the urge to make lightsaber noises while holding it.
Review Krill Lights kindly provided by Kriana.
If you're puzzled by all of the different Krill models, check out Kriana's "how to choose" page.
Here in Australia, Aus PC Market sell the red, green and blue 2-AA size of Krill light, under the Flexiglow brand, for $AU55 including delivery anywhere in the country.
That was a reasonable price when the Australian dollar was worth half a US buck, but the exchange rate has not been kind to it lately. $AUD55 is worth about $US48.50, as I write this.
Direct from Kriana, a single $US29.95 Extreme AA Krill stick shipped to Australia will cost you $US49.95, including $US20 for FedEx shipping. So it's just barely worth buying locally, provided you can get the Extreme sticks here and they're not just trying to shift stock of the old Original models.
For larger orders, though, it's clearly better to buy from the States. If you buy five sticks instead of one, shipping is still $US20, making the total price now $US169.75. Even if you want fifty sticks, air shipping is only $US35.
