The best flashlight is Surefire L2 Digital LumaMax. It's
small, rugged, bright, and long-lasting.
In this article, I cover the selection of battery and flashlight.
I am no expert on batteries and flashlights (not even a hobbyist).
What I collected here is a compilation and derivation of data that
helped me understand the subject; perhaps it will help you, too. I
was just shopping for a light.
Lantern 6v batteries are by far the least expensive source of
electricity coming from a non-rechargeable battery. Nothing comes
close. Type D batteries (very inexpensive, too) are more than twice
more expensive than lantern batteries.
Lithium 123A batteries have very high capacity per gram
(gravimetric energy density). Ignoring AA Lithium, the closest
common contender are types D and C: 2.6 times less capacity per
gram.
AA Lithium batteries have 40% lower capacity per gram than 123A,
are twice more expensive per unit of capacity, and are of comparable
size; avoid anything that uses AA Lithium batteries in favor of
devices that use 123A batteries.
AAAA and N batteries are ridiculously expensive. They are also
hard to get. Steer clear of anything that requires them.
Type F and MN21/23 batteries are rather hard to find as well.
Avoid if possible.
Among common alkaline AAA, AA, C, and D batteries price decreases
with size (fast) and capacity per gram increases with size (slowly).
9v batteries are the same price per unit of capacity as AAA and
have 20% less capacity per gram. Therefore, AAA might be slightly
better than 9v. Note, however, that if batteries are bought retail,
AAA becomes significantly more expensive. These types are comparable;
simply choose the right size (and, by extension, capacity). Or,
better yet, use 123A.
It seems that overall the following types of batteries make the
most sense (for different purposes):
Lantern 6v
Very cheap per unit of capacity, good capacity per gram
(comparable to other alkaline batteries: somewhat better than AAA and
AA, but slightly worse that C and D); but, it's large (certainly not
pocketable). Excellent for work lights or a light in the car, or an
emergency light at home (if a variety with long shelf life is bought).
Type D
Good compromise: cheap (only lantern batteries are cheaper) and
good capacity, not too huge.
Lithium 123A
Not much more expensive than AAA or 9v, very high capacity per
gram, small, very long shelf life.
Rechargeable batteries seem to only make sense if you are a very
heavy regular user. They have no place in emergency and backup
lights. Even if (and especially if) you are a heavy user, you still
need a backup light, to which the considerations of this section will
apply.
Rechargeable Batteries
For a regular user rechargeable batteries offer lower price of energy
(at the price of lower energy density).
Rechargeable batteries come in the following types:
Nickel Cadmium (NiCd) -- the original rechargeable (since 1950),
memory effect if not maintained correctly, decent energy density
(about 50-70Wh/kg), low internal resistance (allowing for high
currents), likes deep cycles and fast charge, toxic
Nickel-Metal Hydride (NiMH) -- newer (1990), 50% higher energy
density than NiCd and 3 to 5 times fewer charge cycles, best to avoid
in favor of Lithium Ion
Lead Acid -- low energy density, fear of deep cycles, essentially
only good for automotive and UPS use
Lithium Ion -- the modern (1991) alternative to NiCd, twice higher
density, no maintenance or memory effect, relatively harmless to the
environment, ages whether it is used or not (useful lifespan 2-3
years)
Lithium Ion Polymer -- a compact (and more than twice as
expensive) alternative to Lithium Ion, somewhat lower energy density,
immature at this point (commercial start in 1999)
Unfortunately, at this time it appears to be impossible to get a
flashlight that would use rechargeable Lithium Ion 18650-type cells.
Large Lithium Ion batteries conservatively provide about 2Wh/cent over
their life time, assuming daily -- or more frequent -- charge cycles
(almost three times cheaper than lantern batteries). They are also
maintenance-free and have energy density only slightly worse than
non-rechargeable alkaline batteries (about 120Wh/kg). Lithium Ion
batteries rapidly become very expensive if used infrequently due to
their aging properties.
NiCd batteries made to fit type D sockets can provide up to
10Wh/cent with regular maintenance. Improperly maintained NiCd would
provide approximately 3Wh/cent. NiMH batteries can yield about
2Wh/cent with proper maintenance.
Lamps
Light Emitting Diodes (LEDs) have very long life (essentially never
needing to be replaced), produce light that can appear more white than
that of other lamps, have very good lumen/Watt ratio. However, they
cannot have very high wattage, and, therefore, even with their good
lumen/Watt ratio cannot be made very bright (the new Luxeon 1W LEDs
seem to be an exception: they can compete in brightness with a
conventional lamp; the coming 5W LEDs may very well obsolete many
incandescent lamps). Since they typically have low wattage such as
100-150mW, LEDs are often combined to produce a flashlight with higher
light output; however, this way they cannot be all placed in the focal
point of a reflector to produce a beam. Several LEDs make a good
flood light, while a single LED makes an excellent key-chain light.
Xenon lamps are used in high-end automobile headlights. They
produce absolutely the most amount of light for their size, if we are
to ignore HIDs. They burn out much faster than LEDs and, of course,
use much more power.
Conventional and halogen lamps appear inferior to Xenon lamps for
serious-beam applications in terms of total output, while they lose
badly to LEDs for flood or small light applications.
Halogen lamps have better than xenon lumen/Watt ratio, so they
might be preferable in a flashlight with only incandescent bulb and no
LEDs. They are also cheaper than xenon bulbs.
High Intensity Discharge (HID) lamps are very expensive (up to $100
per bulb), very fragile (no dropping!), large, and take tens of
seconds to come to full output. They produce a lot of light. The
main application is stationary lights.
Reflectors
LED lights often come with no reflectors at all. However, all `beam'
lights (and most lights in general) are equipped with paraboloid
reflectors. Assuming point light source, an ideal manufacture
process, and no diffraction, the flashlight with a smooth paraboloid
reflector and a lamp in the focal point would emit a perfect beam of
parallel rays. Since lamps actually have non-zero size and
manufactured paraboloids are not perfect (often, they are simply
approximated by spheres to simplify the specification), typical
flashlights with smooth reflectors produce rings and dead spots. The
rings are unavoidable if the light allows for wide beam setting
(moving the lamp out of focus). One can alleviate this problem by
introducing facets or minor random imperfections: the beam will be
smoother at the expense of throw. A faceted reflector consists of a
large number of tiny flat mirrors. A textured reflector has a fine
texture; it is also known as a stochastic or an orange peal reflector.
Faceted and textured reflectors help produce smooth light out of
focus. Textured reflectors work better than faceted (and are harder
to make, so they are found in more expensive lights).
Some reflectors can be combined, so that the outer part is smooth
(resulting in a tight beam with a good throw) while the inner part is
textured to reduce rings in wide beam setting.
Switches
There is the familiar push-button on/off switch, the cap or bezel
twist, and tail-end `tactical switch'. Tactical switch is so known
because this is what police officers and other users of flashlights
for pistol shooting in the dark use; it works by momentarily turning
the light on while the button is pushed in (usually with a thumb). A
bright flashlight can, in addition to illuminating the target,
temporarily blind or dazzle an opponent. [It should be noted that
`serious' types, such as the military, would not use a light for
shooting in the dark at all, since night vision equipment is readily
available.]
The tactical switch is ideal for very bright beam lights: not least
because they use a lot of energy and it is convenient to be able to
turn them off as soon as they aren't necessary. It is almost always
combined with a way to turn the light on and keep it on, often by
twisting the tail cap.
A growing number of lights come with both an incandescent lamp and
one or more LED. These require the selection of a mode for their
operation. Unfortunately, the most common way to allow to select one
of several modes is to provide a button that cycles through the
states. This has the unfortunate consequence that after you're done
using a low-level mode and want to turn the light off (perhaps to
regain night vision) you have to go through a high-output mode that
erases your night vision. A much better user interface would be to
provide an on/off switch (perhaps a tactical switch as described
above) along with a separate selector of modes.
Case Materials
Flashlights are commonly made of plastic, aluminum, steel, and
(synthetic) rubber. Plastics lights (and pure rubber lights) are
cheaper than metal ones, but they do not protect the content well and
are hard to make even marginally watertight. Steel is unnecessarily
heavy. Any light should have an aluminum case with rubber edges for
grip, water protection, and cushioning. Rubber cases can be OK for
cheaper lights that use inexpensive bulbs/LEDs and have no electronics
to protect.
Electronic Parts
Many lights don't have any and are just fine. Many lights need
step-up or step-down circuits; these will often regulate voltage for
constant brightness throughout battery life. Regulated power supply
is a nice thing, except the user has little warning that the light is
about to go out. I'm ambivalent about these.
The Ideal Flashlights
Flashlights fall into three general categories:
key-chain lights for finding a keyhole, lighting a path, avoiding
furniture indoors, etc.;
flood lights to illuminate an area or a room;
beam lights to illuminate remote objects.
Lights that can be used for more than one purpose are convenient
and popular. Traditionally, a combination beam/flood light was
implemented as a beam light with a conventional bulb and an adjustable
focus: when such light is seriously out-of-focus, the beam is wide (in
reality, irregular and unsightly). With the advent of LEDs (which are
ideal for flood lights) these combinations are becoming obsolete.
Further, flashlights can be portable (those that you intend to carry)
and non-portable (for the home, the car, etc.). For non-portable
lights, there's no reason not to provide both flood capability with
LEDs and a beam capability with a xenon bulb and a smooth reflector in
a package that includes a lantern battery (or, more expensively,
several type D batteries). Portable lights are trickier.
In a portable light, at least the choice of batteries is very
clear: lithium type 123A. Nothing small comes close in capacity per
gram, and they are only slightly more expensive than AAA or 9v
batteries (and much cheaper than AAAA, N, or AA Lithium). Ideally, a
portable light should provide a combination of key-chain, flood and
beam. If the light has integrated LEDs, the incandescent bulb will
not be (ab)used for flood light purposes and will therefore only be
used sparingly; therefore, in a LED/incandescent light combination,
xenon bulb makes the most sense since it provides highest total light
output.
The ideal non-portable light:
Anodized aluminum case with rubber inserts for grip, elements
insulation, and cushioning.
One or two lantern batteries.
A large and powerful xenon bulb with a smooth prefocused
paraboloid reflector for very tight intense beam.
Three dozen (or however many fit) LEDs around the reflector under
the lens.
Two modes: a number of LEDs on with xenon light on or off.
Mode selector that can be switched between two positions:
xenon lamp on and off.
A rotating ring with clicks (like an aperture ring) that sets the
number of LEDs on (from zero to all).
Push-button on/off switch.
Comparing this light to existing lights, such a light would have the
following running times: 30 hours in full-illumination flood mode or
7-10 hours in beam mode, depending on whether the LEDs are on.
The ideal portable light:
Anodized aluminum case with rubber inserts for grip, elements
insulation, and cushioning.
One or two lithium 123A batteries.
Xenon bulb with a smooth prefocused paraboloid reflector for very
tight intense beam.
Half a dozen (or however many fit) LEDs around the reflector under
the lens.
Three modes: one LED on at half-power, all LEDs on with full
power, and all LEDs off with xenon lamp on.
Mode selector that can be switched between three positions
indicating three modes of operation.
Tail-end tactical switch.
Comparing this light to existing lights, such a portable light with
one 123A cell should have the following running times: about 300 hours
in keyhole mode (comparable to low-output mode of the PAL), 10 hours
in flood mode, and 1 hour in beam mode (with output similar to the
E1).
It is too bad that as far as I know no-one makes either of these
lights. The absence of a good combination non-portable light can be
tolerated: the light would already be huge, why not keep separate
flood and beam lights? The absence of an ideal portable light is
regrettable.
Existing Models of Portable Lights
Some interesting flashlights:
Lifestyle Fascination Aluminum Xenon/LED Hand Torch
Unknown manufacturer, possibly exported by a Taiwanese company
Nuwai; reportedly very sturdy construction. Costs $40 plus shipping
with two 123A batteries and a faceted plastic reflector, has three
modes: 3 LEDs (26 hours), 6 LEDs (9-12 hours), xenon (1.75 hours).
Comes very close to being perfect, but has an annoying
cycle-through-three-modes push-button switch and is a bit too large.
In the same league for center brightness as the Scorpion and the 6P
(is about 30% dimmer than these lights).
Streamlight Scorpion
Supposedly similar to the Lifestyle Fascination light in xenon
mode, but has no LEDs and comes with a well-designed tactical switch
and a spare bulb. About $40.
Princeton Tec 40
A submersible halogen light with four easy-to-find AA batteries
(3-5 hours), plastic case, and a textured reflector for $16. Quite
bright. (Supposed to be in the same league as Surefire E2 for center
brightness.) Very economical (but not the smallest) tight beam light.
Excellent backpack light, I suppose.
Surefire E2
Very small bezel (and very small two 123A battery light overall).
Otherwise, similar to Streamline Scorpion with less focused beam and
with a price tag of $75.
Brinkmann Legend LX
Another xenon light with two 123A batteries for about an hour of
runtime. People complain that the bulb falls out; otherwise,
well-built. Tail-end on/off switch. Supposed to be $20 at Walmart
and $30 on the net.
Surefire E1e
Single-cell version of the E2. The smallest bright light (an hour
of run time, twice less bright than E2). Gets all the rave. Huge wow
factor for $70.
PALight Survival
Single LED with a reflector; 9v battery; about $20; low (200
hours), high (40 hours), and strobe (200 hours) modes; rubber case.
Another beam LED light. Has the distinctive advantage of long run
time and a distinctive feature: always on low-level glow.
Surefire 6P
Killer xenon light for $75, made mostly for the police. Two 123A
batteries give one 60 minutes of light. However, unless you're going
to buy the P61 high-output lamp assembly (HOLA) that only works 20
minutes on these batteries, forget it: Streamline Scorpion for $40 is
very similar and comes with a spare bulb that can be carried in the
light. (The ``forget it'' part does not necessarily apply if you
actually want it for tactical use, where extra ruggedness can very
well be worth it, while extra bulb in the light is not very useful.)
Some not so interesting but popular flashlights:
ARC-LS-123A
Uses the right battery, has single Luxeon 1W LED with a reflector
and a package that is supposed to be very well built; the ideal
key-chain light, right? Wrong. It's $120-150. Get a Surefire E1 if
you're into super-expensive key-chain lights: it has a tighter beam and
is twice cheaper.
Streamlight Stylus
Keyhole light for $20: Single LED, no reflector. Pen form factor
(convenient if you have pen holder pockets). Uses three outrageously
expensive AAAA batteries. Forget it unless you are the type to take
apart Duracell 9v cells, take out the (almost) AAAA cells and insert
spacers. Supposed to be well-built, but who cares?
Inova X-5 Tactical
A well-built 5-LED beam light? Well, apparently it doesn't have
any throw (how could it?), but works poorly as a flood light, too.
Have some $50 to waste?
Conclusion
I'll wait for Luxeon 5W white LEDs. They'll probably cost around
$30 retail and have light output of 120 lumens (same output as the
HOLA option of Surefire 6P, but larger than xenon bulb, so beam would
be wider with less intensity for the same size reflector); but, on the
same two 123A cells they'll burn for an hour rather than 20 minutes.
Rumor has it that their white version has some 1000-hour problem that
should be corrected perhaps in early 2003. Once the LED is available,
a number of flashlight manufacturers in likely to take advantage of
it.
In the meantime, I'll use assorted lights; maybe I'll buy the
Princeton Tec 40.
Update: September 2003
Since the last time I checked, two things happened: the 5W LEDs
started to show up in production lights and a new light that pretty
much answers my call for a combination light came out. Both
innovations are produced by Surefire. Their flashlights are very
highly regarded by the experts (of which I am not one).
The 5W LEDs did not turn out to be the wonder they were touted to
be, but they are still really good. Their rated life
expectancy is 500 to 1000 hours for different versions (so, they may
need replacement, but the cost of the LEDs is negligible compared to
the cost of batteries). They have better lumen/Watt ratio than xenon
bulbs, but the difference is not as great as was expected. But they
are shock-proof. Xenon lamps with outputs up to those found in lights
up to 6P are essentially obsolete at this point.
Surefire A2 Aviator has a xenon bulb plus three standard 5mm LEDs.
It has two modes (LEDs only and xenon lamp plus LEDs), regulator,
soft-start for the xenon bulb, and is otherwise similar to the E2.
$140.
Surefire L4 Digital Lumamax (and KL4 bezel for any E series light)
has a single 5W LED and blows away any xenon-based E series flashlight
in light output (but not in center luminosity) while having very
similar power consumption. One intensity level only. Regulator that
results in constant light output for about an hour. $140.
Surefire L1 with a single 1W LED and a two-stage tail switch is
otherwise similar to the L4. $100.
All of the above lights take two CR123A cells.
What I want now is an L4 variant with two-stage switching mechanism
to be able to save battery.
Update: May 2005
Surefire has granted my wish in its L2 LumaMax: two-stage switch and
more total output on ``high'' (100 lumens) than L4. One hour on
``high'' or 18 hours on ``low.'' $165, more expensive than anything
mentioned above. Some minor nits include the fact that it's a bit
longer than other two-cell lights and supposedly makes a high-pitched
noise on ``low.'' About as good as it gets. They also have the U2
Ultra ($270, whew!), which has more levels of output, but isn't as
bright as the L2 at the highest setting and is larger and heavier; not
sure who would buy it.
Update: November 2005
Since nothing major (like a one-element 5-W LED) seemed to be coming
out, I bought the Surefire L2 Digital LumaMax flashlight. I can find
no fault with it. I'm sure a more miniature version with less light
output will be coming out one day.
I am no flashlight expert. This document is an amateur's personal
opinion only.
