Review on ThruNite TH20 520 Lumen CREE XP-L LED Headlamp Flashlight -Lightweight Waterproof IPX-8 EDC Headlamp For Indoor & Outdoor Hiking,Camping, Cycling - NW by Bryce Marshall

This is just my initial impression and use, I'll update in a few months. This initial review is using a basic AA alkaline battery.EDIT - Update #1: With the Lithium Ion 14500 battery, on Turbo, this headlight throws some serious light. Seriously, I've never had/seen such a powerful headlamp before. I know of course there are even more powerful/brighter ones out there, but the limited research I've done on them is they start around $60. I can't see why I would need to travel with more than one battery on typical backpacking trips (3-10 days), except perhaps in winter when light is so very critical and a dead battery could be very bad news.Update #2: This is my first experience with using li-ion in a light. Not sure if it is the protected 14500 I am using or the TH20's own built-in protection, but the light cuts out suddenly at 3.0V. It doesn't dim, just cuts off, which (news to me) to simply how li-ion batteries work. You absolutely need to carry a back-up battery if in the woods with this (which good advice anyways, but it's essential in this case).Update #3: Following up on Update #2, I tried a different 14500 battery. For #2, I was using the Orbtronic 840mAh 14500, which is rated for a draw of about 1.7A. The TH20 can pull up to 1.5A on Turbo. I've since learned that it's best to have a battery rated at least twice the draw of the device it will be used it, in this case it would be a 3A rated 14500. So I bought the Efest 650mAh 6.5A 14500. I ran the headlamp on Turbo for over 30 minutes (Thrunite's owner manual says limit it to 10 minutes on Turbo) before turning it off. The headlamp got very warm, almost too warm to touch. I doubt I did any damage, but I now feel more confident using Turbo mode with a li-ion 14500 installed. BTW, one review said he was getting reading of 800mAh on said Efest battery on his Opus BT C-3100 analyzing charger.Update #4: I've since corrected a few statements in my review below, such as I had previously incorrectly stated that the battery couldn't be locked out (it can with a 1/4-turn loosening twist of the battery cap).Update #5: Long story short, I don't recommend unprotected 14500 cells in this light for beginners of li-ion cells. I was having trouble with the lamp and checked the voltage of the unprotected Efest 14500's. It read 1.2v, checked on a second multimeter. Li-ion cells are stable down to 2.5-2.8v, so 1.2v is a significant over discharge. Some battery experts convinced me that while what I did wasn't ideal, I just needed to keep an eye on it and charge it very slowly at 200mA or less. I placed it in the Xtar VC2 Plus charger, which will start charging at 100mA for overly discharged li-ion cells until it reaches 3.0v then will switch to 500mA. Once it switched, I removed it and then charged it in the Opus C-3100 at 200mA, which is better for a small cell like a 14500's. The cell charged fully and internal resistance seems normal. If any of this is Greek to you, then you're better off sticking to protected cells. Why did the cell get so discharged if the TH20 has built in low voltage protection? According to Thrunite customer service, 1.3v is the cutoff point for li-ion cells and 0.9v for NiMH. Why they did it at 1.3v I have no idea. It should be more like 2.8v. I'm removing one star from my rating for this design flaw./end EDITPros: solid construction, very bright, very adjustable brightness, intuitive mode switching, true neutral (warm) color light, spare parts, uses only one battery, option for li-ion 14500 for brightest turbo mode, built-in reverse polarity and low-voltage protection, battery lock-out by loosening tail cap, excellent valueCons: tad heavier than I'd like for backpacking, spare parts don't include rubber power button, turbo mode not to be used more than 10 minutes (I've gotten 30 minutes without noticeable issue using appropriate battery)This is my first solid metal headlamp. I've grown tired of the short lifespan of plastic based headlamps. Though while the solid aluminum construction of the TH20 is welcome, I do wish the walls were slightly thinner to save a bit of weight.I'm particularly pleased by the neutral white color this lamp throws. Definitely has a yellowish tint, which I prefer. I despise all things blue light aka cool white.The button presses are fairly intuitive. Press on and off. Once on, press and hold to ramp the brightness up or down; release and repeat to ramp in the other direction. When off, long press to turn on ultra low power Firefly mode (this is as fave feature of mine), then quick double press to rocket to turbo mode (highest brightness), another double press turns on SOS signaling.I love that the Firefly mode can be accessed directly. When camping, I often don't need super brightness and prefer to preserve my night vision by using as dim light as possible. It seems that Firefly mode will fit this bill perfectly.I like the light pattern: a brighter spot in the middle and a wider diffusing halo around the spot🚙Note that the extreme brightness of Turbo mode is 250 lumens on AA and over twice that on a 14500 battery. Waiting for a 14500 in the mail, but Turbo on AA is already more brightness than I'll typically need. I was able to see pretty good all the way up a 80 foot tall pine tree. The instructions do warn not to keep Turbo mode on for more than 10 minutes to protect against overheating. I suspect this is most crucial with the 14500 battery, I will test temperatures with the infrared thermometer later and update.Finally, this is a screaming deal for the quality. I have paid nearly twice as much on plastic head lamps that had not near the quality or features. I cannot see any reason to ever buy a plastic-based headlamp ever again with such durable, brighter and better electronics like this on the the market for $29.