Available from StenLight.com

Spelunking (the exploration of caves) is well known to be one of the roughest and most demanding of activities that outdoor gear can encounter. Muck, mud, rock and water all come together in a concentrated effort to destroy everything you have on your person and quite possibly kill you in the process. High quality, durable gear is essential. It must be able to withstand repeated drops, sand and mud in the moving parts, water everywhere, and occasional smacks into abrasive rock walls. If I were going into this type of environment and had to choose a headlamp which could withstand this sort of abuse, the Stenlight S7 would be on the top of my list.

Now, I will qualify my comments a little to give the reader some perspective. I do not spelunk. In fact, the last cave system I ever went into was the Howe's Caverns in upstate NY which is really nothing more than a well lit walking tour on flat, dry cave floor which is accessed by an elevator. However, I have several years of camping, hiking, backpacking and very-off-road mountain biking experience. All of these experiences were through some pretty rough terrain, frequently off-trail, and as a result I have a very good understanding of what high quality, durable gear is all about and how valuable it can be in less-than-optimal conditions.

Body: The first thing you notice about the Stenlight S7 is that it's very small. The second thing you notice is that it is built like a very small tank. The body is aluminum and stainless steel. There is a replaceable lens window on the front which is held in place with six 1/16" hex screws and includes a rubber seal to block out the environment. On the back of the lighting unit is the helmet attachment blade which is attached by a hinge to the unit.

The oversized switch is on the left when worn on the head and rotates around the curved side of the light module through 5 positions, each 45 deg. from one another. First position is off (0°), second is low (45°), third is medium (90°), fourth is high (135°) and fifth is turbo (180°).

The unit is powered by a lithium-ion rechargeable battery pack which is connected to the lighting unit by a short cord and a plastic connector.

Bezel/Head: The front of the light has the lens retention plate with its six screws, environmental seal, and lens window. Behind the window are two collimating lenses which collect the light from two 3W Luxeon LEDs. One lens is 5°, the other is 15°.

Additional optics are available from LEDSupply.com if you would like to change the beam pattern provided by the stock 5 and 15 degree lenses. You must use the L2 type optics for proper fit.

Output: The white light produced by the LED is a high color temperature and produces good color rendition. I was unable to detect any significant color tint in these LEDs. The beam is a combination of the 5 and 15 degree optics which gives a combination of medium and narrow spot lighting. The beams overlap at any significant distance from the user and as a result you really can't tell that the light is projected by two separate lenses.

The long-throw switch allows for selection of light output level. Low provides more than enough light for close-up use. Turbo is really intended for occasional use and in still or warm air a thermal limiting system will decrease output automatically to prevent damage to the LED from heat buildup.

Update from StenLight regarding Turbo mode, sent to me after the review:

You stated that "Turbo is intended for occasional use". This is true, but we should explain this a bit more. The S7 is perfectly capable of running in full Turbo mode indefinitely given sufficient power and cooling. If there isn't enough airflow to keep the lamp cool, thermal limiting gradually pares back the power to whatever extent is necessary to prevent the internal temperature from exceeding 65 degrees C (149F). In a cave environment, Turbo is typically used sparingly to conserve batteries and because you don't usually need that much light. But on a bicycle with a larger battery, you might well run in Turbo mode for many hours at a stretch; and the extra air flow keeps thermal limiting from being a factor.

Beam at one meter at target center

Runtime Plot: A picture is worth a thousand words. Dead flat regulation for over 8 hours while in high mode using the rechargeable Lithium Ion battery pack. This is right in line with the manufacturer's claims. This curve demonstrates the use of a very good regulation circuit. Use of medium and low modes will result in much longer runtimes. Use of turbo mode will result in a shorter runtime.

More information on runtime plots is available HERE.

Switch: The switch consists of a stainless steel rotating plate with a bent blade that hangs over the edge of the light body for easy manipulation. Hidden inside the back of the light on the rotating plate is a magnet that actually activates the various modes. Moving the switch blade rotates the ball-bearing equipped switch plate, which moves the magnet to the next detent position. Since the switch uses magnets instead of physical contacts, the switch plate and assembly do not penetrate the body at all. This means there are no holes for water entry through the switch area.

Seals / Water Resistance: The Stenlight is rated for 20 feet of water submersion. This is only guaranteed if the seals are inspected at the factory. Removing the front lens window voids the guarantee, but if you are careful and make sure the seal is properly placed and clean, you shouldn't have any problems.

The battery pack is also sealed against the entry of water. However, the connector between the battery and the headlamp is not. You should open the connector and shake/blow it out really well if it gets wet to prevent the contacts from corroding. A liberal application of silicone grease would probably help out and would make the contacts fairly water resistant. Also, the battery should not be submerged for extended periods of time.

If it gets wet inside you have two options. You can open it up and let it dry before using again, or if you did not tamper with the seals or abuse the light you can send it back for in-warranty inspection (provided it is still in the warranty period).

Ergonomics: Since I do not yet have a headstrap and I don't have a helmet, I can't show head shots. However, you can see in the perspective picture below just how small the light module is. It is incredibly simple to operate with the oversized blade switch and long throw of the switch. The entire unit is very lightweight.

Size compared to a common 2AA aluminum light

Batteries: A rechargeable lithium-ion battery pack powers the headlamp. The pack is rechargeable and the charger has an indicator LED to let you know the state of charge. Red is charging, yellow is mostly charged (about 1/2 hr to full charge) and green is fully charged. Do not leave the battery on the charger for extended periods and disconnect it from the charger when not being charged even if the charger is unplugged. It takes about 3 to 4 hours to recharge a fully depleted battery.

As a result of some accessories on the market for the StenLight S7, you can power the light with a 9V battery or six AA cells. The light is designed for 6 to 18 volts (7V minimum for turbo mode) so you can add your own power supply, but be careful of polarity - damage due to reverse polarity is not covered under warranty. All of the factory connectors are correctly polarized and cannot be connected backwards.

Accessories: A non-helmet headstrap, bicycle handlebar adapter, and multi-voltage adapter are all under development. Currently available accessories include two kits; a Spare Parts Kit and an Accessory Kit with different power options. The Spare Parts Kit contains Front Screws (6), Front Window (with protective film on both sides), Hex L-key, Gasket, Detent Ball Bearings (2), Rear Screws (2), and Detent O-rings (2). The (power) Accessory Kit includes a 9V battery adapter, AA battery adapter (6 cells), and 1 meter extender cable.

I did purchase the power Accessory Kit, and it came in today. The headlamp can run on a 9V alkaline battery (intended for back-up use only) and works fine with the 6 AA cell pack. You should be able to use alkaline, lithium or NiMH rechargeables in the AA pack.

I also purchased a ProLite headband (from Inner Mountain Outfitters), which is intended for another helmet-only headlamp. This also came in today. The construction is pretty cheezy, the battery is loose when stored in the rear loop, and the cable sticks way out on the side, but it does work and allows you to use the headlamp if you don't have a helmet to mount it on. When StenLight makes a headband, I'll get that one and try it out as well.

What I Liked: Waterproof, Tough/impact resistant, Regulated, Long battery life, Bright, Easy battery change, Lightweight, Switch easy to use.

What I Didn't Like: Nothing

Picky Little Things: Non-helmet headband was not available at time of review from the maker.

Conclusions: Simply the best. If you need a near-bulletproof headlamp, this is the one.

Want Another Opinion?: Check out The Trotto Review's opinion of this light. John is a spelunker and has taken the light underground for some practical-use testing in places where it was meant to go.

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