For some odd reasons, I personally have never liked 1 x AA format flashlights. I’ve literally purchased no less than a dozen 1 x AA flashlights in the past few years, and I ended up selling all of them in the secondary marketplace. Some I didn’t like the size or weight, some I didn’t like the user interface (UI), and some I just didn’t like the way they looked physically. I even had problems with the initial release of the Nitecore Defender Infinity (NDI). I got my first NDI back in November 2007 when they first released and I had to return it because they had some bugs in the circuitry (yes even flashlights have bugs like software now). This is my second NDI that I purchased around December 2008, and so far, I have not encountered any problems with it. This is my one and one 1 x AA flashlight. This is among the few flashlights that I alternate in carrying and using on a daily basis.
Before my review, let’s talk briefly about Nitecore. Nitecore is manufactured by EdgeTac, a company operating in China. Despite the stereotype that China only manufactures inferior products, this is far from the truth with EdgeTac. They only started back in 2007, which make them a relatively new company in an already saturated illumination world. EdgeTac released their first product, Nitecore Defender Infinity, back in November 2007. Though it had some UI issues, it was a home run. Since then, they’ve developed several innovative, high-end flashlights, which include the Nitecore D10 and Ex10, both have licenses to use Don McLeish’s patented piston drive switching mechanism.
The NDI is my first flashlight that allows me to program the level of brightness that I need. It has an infinite brightness setting that allows you to customize the level of brightness of your light anywhere from 3 lumens to 130 lumens. Operating this light is quite simple. The flashlight is turned on and off by a forward clicky switch located on the rear of the flashlight. The flashlight will turn on max if the head of the flashlight (bezel) is screwed tight. Unscrew the bezel just a tad, and it’ll turn on to your custom setting. Of course, you do not need to turn off your light to change the setting, you could go from max to custom while the light is on.
Setting the brightness level is quite easy as well. Starting with your bezel slightly loosen, turn on the flashlight, tighten the bezel, and then loosen the bezel immediately (in less than one second). The flashlight’s brightness will start to ramp up or down (6 seconds from min to max). Once it reach the level you want, just turn off the light and it’ll remember where you set the light at. An additional feature the light has is the strobe mode. I personally never found this feature useful. To go to strobe mode is similar to customizing the brightness. However, you will start from tighten bezel instead. Loosen the bezel and tighten it within one second, and the light will go on strobe mode.
Nearly all incandescent and lower-end flashlights that the average consumers are accustomed to runs on direct drive. This means that the flashlight will start off at maximum brightness and the brightness level will go on a downward slope and diminishes every second the flashlight is on until it runs out of battery. On the contrary, NDI and most high-end lights have a buck/boost regulated circuitry. This means that the flashlight will start off at maximum brightness, the brightness level will drop slightly the first few minutes, but then it will maintain a constant level until it runs out of battery. Once the battery voltage level drops beyond a certain point, the flashlight will either goes off or will operate at very dim level (1 lumen or less). There’s a graph on the bottom to explain what I mean. The buck/boost circuitry also provides the users with battery options. Although the NDI is capable of running on 1.5v Alkaline batteries, it is not efficient. Ideally, the NDI should run on 1.2v rechargeable Nickel metal hydride (Ni-MH) , 1.7v non-rechargeable lithium batteries (Only Energizer makes them), or the most efficient option is to use 3.7v 14500 Protected Lithium Ion (Li-ION) batteries  (Please be sure to read footnote #3 regarding the potential danger of Li-Ion).
- Size: 3.7″ (95mm) x 0.79″ (20 mm) Bezel
- 1.40 ounces
- Runtime: Ni-Mh AA – 130 lumens (max) for 50 minutes, 3 lumens (min) for 45 hours
- Runtime: AW Protected 14500 Li-Ion – 130 lumens (max) for 80 minutes, 5 lumens (min) for 60 hours
- OSRAM Golden Dragon Plus high-efficiency LED
- Torch Lumen 130 lumens (See Footnote )
- Impact-resistant optical lens with anti-reflective coating on both sides
- Military grade aluminum alloy with Mil-Spec Type III Hard Anodized finish (HA). – Mil-Spec Type III HA makes the flashlight extremely scratch resistant.
- Resistance to impact by dropping according to US MIL-STD-810F – The flashlight will not fail if you drop it repeatedly from a certain height.
- Waterproof to IPX-8 standard – The flashlight can immerse in water of certain feet for a certain duration.
- Broad-voltage fully-regulated circuit, compatible with kinds of batteries
- Li-ion battery identified and low-voltage alarming system
- Unique Infinitely Variable Digital-controlled Brightness System
- Two-stage memory function, can be switched easily
- Tactical forward clicky switch
- Anti-rolling rugged design
- Metal reflector
- Ability to accept all AA-size battery type
- Programmable to the setting you wish
- Long runtime at minimum level making it an ideal emergency light
- Rugged designed that’s drop proof and waterproof (to a reasonable extend of course)
- Knurling to prevent flashlight from slipping when your hands are moist or when the light is wet
- Price – not a light the average consumer will consider cheap
- No options for pocket clip
- Crenalated bezel – designed for tactical application where you could use the flashlight’s head as a last ditch impact weapon (like a kubaton). The bezel is a little too pointy for my liking.
- OSRAM Golden Dragon Plus LED – this led has a very smooth beam pattern that I like. However, the color tends to lean in the cool side. It doesn’t bother me, but some people rather deal with the notorious CREE ring than the cool white of the Golden Dragon Plus.
- Potential UI Bug – My first NDI had some UI bugs. It would ocassionally swtich to strobe for no reasons. I appears that EdgeTac has addressed this UI bugs, since no one has complain about it.
Rating: 5 out of 5
 Alkaline batteries are poor choice to be used in conjunction with high-current drawing electronic devices. This is because Alkaline batteries have high internal resistance, and thus instead of providing the power source necessary to run the electronic devices, the power gets lost in the form of heat energy.
 Nickel Metal Hydride (Ni-Mh) have lower internal resistance, making them ideal for high-current drawing electronic devices. One caveat, however, is that Ni-Mh self-discharges quickly. In other words, it is typical to expect a 25% reduction in power every month even if it’s not used. You should expect the battery to be out of power within 3-4 months. Over the past few years, battery manufacturers have come out with low self-discharged (LSD) batteries. The companies claimed that the LSD batteries can maintain 80-85% of their charge even after one year. I’ve tried a couple of brands, and the one that seems to be very good is Sanyo Eneloop (also recommended by many hobbyists).
 Please do not use 3.7v Li-Ion batteries without doing a little research and understand the potential danger. The chance of explosion is extremely rare considering the millions of Li-Ion batteries that are used in cell phones, laptops, iPods, etc. However, you should be cognizant and use these batteries with care. Although the battery technology has significantly improved over the years, there’s still a possibility that mishandling these batteries could cause it to vent and explode. Although they are in the same shape and size as an AA battery, they will fry any electronic devices that are not capable of handling such high voltage. Never recharge these batteries in regular Ni-MH rechargers. Never leave the batteries charging overnight or while you’re away. Never buy lower-priced inferior batteries. Avoid using unprotected Li-Ion batteries. The protected Li-Ion has an internal circuit and shuts off the battery when it goes above or below a certain voltage. At the time of this review, many people, including myself, recommend AW Protected 14500 batteries for the NDI. You could purchase them at https://www.4sevens.com/product_info.php?cPath=53&products_id=206. Be sure to purchase the Li-Ion chargers if you don’t already own one.
 Many flashlight manufacturers promote their lights by claiming that they’re capable of producing x amount of lumens. This is a gray area in terms of false advertising. The flashlight manufacturers are simply providing the total number of lumens coming from the emitter (LED) when driven under a certain amperage, under the ideal conditions. The moment the LED turns on and heats up, the lumens will drop. You’ll also lose light depending on the opacity of the window (lens). You’ll lose about 20% light from Polycarbonate windows. In other words, a 100 lumen flashlight under the ideal conditions, will produce only 80 lumens the moment it passes through the window. Even with the highest transparency optical grade Ultra Clear Lens (UCL), you’ll lose at least 2% of light. If the window is not anti-reflective coated, you’ll lose even more since the light is reflected backwards instead of going out through the window. Unless the flashlight manufacturer states that the lumens is “out the front” or “torch” lumens, it is safe to take whatever the lumens number a flashlight manufacture state and reduce it by 40-50%. In other words, if the flashlight manufacturer claims that the flashlight produces 200 lumens, then it means that the out-the-front or torch lumens is between 100-120 lumens. The only exception is Surfire who underrates their lumens. I have seen Surefire 65 lumens flashlight being noticeably brighter than XYZ’s flashlight with 200+ lumens.