Review: Armytek Prime C2 Pro XHP35, a versatile 18650 EDC light

This Armytek Prime C2 Pro XHP35 (warm) was provided by Armytek for review. Use coupon code RED at http://armytek.com and http://armytek.ca for 10% off regular-price flashlights. There is an active promotion on Prime models, and this model is currently $74.70 instead of the usual $90.

Many photos and beamshots in the album

Quick Review

The Prime C2 Pro XHP35 is the most powerful, and most expensive model in Armytek's EDC line. It uses a single 18650 Li-ion battery, two CR123s or two 16340 or 18350 Li-ions and features a well-designed UI offering shortcuts to low, medium and high modes from off. Other models in the Prime line can use one or two AA batteries or one CR123. All Primes offer a choice of cool ("white") or warm tint; this is the warm version.

http://imgur.com/K6gJmCD.jpg

This version of the Prime is a bit long for a 1x18650 side switch light at 124mm, but it's not hard to see why. There's a large, very strong removable rare-earth magnet in the tail, with its own compartment and screw-off cap. The bezel is very deep, giving more protection for the lens. The battery tube is long to accomodate significant variations in battery length. The spring is long and stiff to ensure reliable contact even if the light is shaken, though there can be some side to side rattle. The threads on the battery tube are longer than most lights, and there are dual O-rings for improved waterproofing. The Prime is longer than most of its competition, but it gains ruggedness and versatility for it. I think that's a fair trade, but it may not be the light for someone with shallow pockets. For me, this length is comfortable for pocket carry. The pocket clip is quite secure, though it can require some wiggling to fully insert into a pocket. The finish is a matte annodizing that provides good grip. While thick and tough, it did scuff a bit under the pocket clip.

Comparison with other lights - Convoy S6, Convoy S3, Zebralight SC63w, Prime, Thrunite TN12

The XHP35 emitter is rare in smaller lights, as it requires either four Li-ion cells or a boost driver to power it. The Prime's boost driver is highly effective, maintaining stable output in all modes as long as the light isn't overheating and the battery can handle it. The manual recommends batteries rated for 7A or more, but the light detects, and reduces output to protect batteries when voltage drops too rapidly. Armytek's protected 3400 mAh cell, almost certainly based on a Panasonic NCR18650B cannot. The protection doesn't trip, but the light starts throttling output after about 10 minutes due to the voltage sag such a high load puts on the battery.

http://imgur.com/qnvLJCI.jpg

Heat is an issue on the highest mode; my usual fan cooling was insufficient to prevent some small thermal stepdowns. I ended up testing with the light submerged in water to see if the driver could really maintain full output. It could, but real-world situations in which that much cooling is available are rare. The Prime is not intended for use as a dive light, but showed no signs of leaking during its underwater runtime tests. Maximum output is best thought of as a burst mode usable briefly with the second-highest "turbo1" mode as the default high.

http://imgur.com/733axqZ.jpg

The tint of this emitter is very unusual. Complaints about green off-tints in lights using a domed XHP35 emitter have been common since its introduction, but there's none of that here. This is the rosiest white LED I've ever seen, exceeding even the famously rosy Nichia 219B sw45k. /u/maukka is testing the same model and shared some data with me: 4050K, 73 CRI and a chromaticity coordinate putting it in Cree's 5R tint bin. We both got lumen numbers lower than advertised, and his, with more precise and better-calibrated equipment were lower than mine. The beam is a little ringy on a white wall, but I didn't notice it using the light outdoors.

http://imgur.com/HPTDR4C.jpg

The user interface is one of my favorites in the whole flashlight industry. A single click turns the light on in the last-used mode, or off. Double-click is medium. Triple-click is high. Quad-click is blinky. Long-press from on cycles through the sub-modes of the current group. Long-press from off starts in the lowest mode and then steps through all modes except for the highest. Blinky modes are strobe, high beacon and medium beacon. There's also a momentary-only "tactical" mode using the last-used mode, accessed by holding down the button while loosening the tailcap.

Overall, I really like this light and would recommend it to anyone who wants a reliable, durable, versatile flashlight, as long as they're not a tint snob.

    • Great user interface
    • Robust build quality
    • Strong magnet holds securely to steel surfaces
    • Excellent output stability
    • Good thermal regulation
    • Excellent protection for batteries
    • All 18650s fit and make contact reliably, even when the light is shaken
    • Very low minimum mode
    • Great mode spacing
    • Essentially zero standby drain
    • Advertised output may be a little optimistic
    • Pink tint
    • Ringy beam
    • Very long for a side-switch light
    • Battery rattle

Details and technical analysis

Accessories

Included with the light are a holster, lanyard ring that installs under the magnet cap, lanyard, pocket clip and two spare o-rings. The holster has a plain belt loop with no velcro, and elastic sides. It's adequate for basic use, but doesn't attach to MOLLE.

http://imgur.com/tVFpMPR.jpg

Modes and user interface

There are 8 regular brightness levels split into three mode groups, which the manual calls "firefly", "main" and "turbo". I'd call them low medium and high, but I'll use the manual's terminology here for consistency.

State Action Result
Off Short-press Last-used mode
On Short-press Off
Off Long-press Firefly1
Off Longer-press Ramps up through all modes, stopping when the button is released or at turbo1
On Long-press Cycles through each mode in the current group
Any Double-click Last-used medium mode
Any Triple-click Last-used turbo mode
Any Quadruple-click Last-used blinky mode

While the Prime does have a lot of modes and a somewhat large number of UI actions, I find this UI intuitive in practice and rarely get unwanted results. It's always possible to get to lower modes without passing higher modes and to get to the turbo group quickly when desired. If last-used in a reasonable mode, the Prime can be handed to others with no instructions and they'll be able to turn it on and off.

A status light under the switch blinks green, yellow or red every few seconds when the light is on to show the battery level. This can be enabled when the light is off by loosening the tailcap, holding the button, tightening the tailcap, loosening it again, then releasing the button. Repeating this process disables it. When the light is warm, the indicator light uses three rapid blinks in yellow in place of the single blink. Hotter still and the blinks become red.

Output and runtime

Runtime in the maximum mode depends greatly on cooling. I don't think moderately cool or windy conditions would be sufficient to maintain maximum output for more than a few minutes. The cooling fan I've been able to use to keep every light aside from a FET triple from overheating was insufficient to prevent some stepdowns with the Prime. Immersion in water was the only way I could keep it from stepping down, but extreme cold and wind or rain might also prevent stepdowns.

Output is reduced if the battery voltage drops too rapidly, as is likely when the maximum mode is used with a low-drain battery like the popular Panasonic NCR18650B on which most 3400 mAh 18650s, including Armytek's are based. Medium to high drain batteries such as the Sanyo NCR18650GA, LG HG2 and Samsung 30Q are better-suited to this light. When the battery hits about 3.0V, the output is reduced until the voltage rebounds. If it does not, the main LED blinks once to let the user know the light will soon step down to its lowest output. It can maintain firefly1 on a low battery for many hours before shutting off completely at about 2.6V to avoid over-discharging the battery.

I measured output and throw using Ceilingbounce on my Nexus 5 and an integrating shoebox calibrated using other lights with reasonably trustworthy output numbers. I will be recalibrating with data from maukka for future tests, but these are with the old calibration. With more precise and better calibrated equipment than I have, maukka has measured numbers lower than I did here for the same model. If it was just my own crude measurements, I'd be hesitant to call this light out for underperforming, but with maukka getting even lower numbers, I think it's fair. The intensity I measured does match the claimed throw. These are the claimed outputs:

  • Firefly1: 0.15lm
  • Firefly2: 1.7lm
  • Firefly3: 6lm
  • Main1: 35lm
  • Main2: 180lm
  • Main3: 420lm
  • Turbo1: 950lm
  • Turbo2: 1581lm, 187m FL1 throw

Measured output and runtime are as follows, conducted with an LG HG2 3000 mAh high-drain 18650 unless otherwise noted:

Mode Lumens FL1 throw Graph Time to 80% Time to 50% Time to 10% Tailcap current
Standby 0 0 - 45 years 45 years 45 years 7.5 uA
Firefly1 0.15 (claimed) - - ~201 days ~201 days ~201 days 0.62mA
Firefly2 1.7 (claimed) - - ~37 days ~37 days ~37 days 3.41mA
Firefly3 6 (claimed) - - ~11 days ~11 days ~11 days 11.22mA
Main1 34 (measured) 29m - ~38 hours ~38 hours ~38 hours 78.5mA
Main2 138 (measured) 58m link 503 minutes 505 minutes 541 minutes 352mA
Main3 312 (measured) 87m link 202 minutes 203 minutes 237 minutes 775mA
Turbo1 696 132m link 72 minutes 74 minutes 77 minutes -
Turbo2 1299 186m link 26 minutes 28 minutes 32 minutes -

Current was measured with a battery over 4.1V and will be higher at low voltage because the Prime has a boost driver, so these estimates may be a little optimistic.

As the high modes vary greatly on cooling and batteries, here are some other test conditions:

Mode Cooling Battery Graph Minutes to 80% Minutes to 50% Minutes to 10%
Turbo1 Water Armytek 3400 link 17 35 51
Turbo1 Fan LG link 30 32 35
Turbo1 None LG link 3 3.5/6/10 86
Turbo2 Fan LG link 72 74 77
Turbo2 None LG link 77 79 81

And some other graphs:

Beam and tint

The tint is very rosy, a 5R tint bin according to Cree's chart. According to maukka, CRI is 73, about average for neutral/warm LEDs with unspecified CRI. Color temperature is 4050K. It noticeably washes out greens in favor of reds and browns and sometimes makes white objects look pink. I find it more pleasant than green off-tints or cool whites over 6000K, but this amount of red is still an off-tint that hurts color quality.

The TIR optic produces a beam similar to that of a reflector, but has more prominent rings than most reflectors. Both intensity and color vary in the rings. This isn't nearly as noticeable outside as it is on a white wall though, and I wouldn't consider it a major complaint.

Overall the beam is a bit of a disappointment on an otherwise excellent flashlight.

Ergonomics

The Prime is a little long, but feels good in the hand and is still shorter than most tailswich lights. The finish has a matte texture a bit like a chalkboard. It provides good grip, wet or dry, with or without gloves. I like it, but I've seen one or two people write that they do not. The switch is easy to find by feel, and there's a notch on the opposite side of the head that's a natural place to put a finger. The pocket clip is secure, and overall, this is a comfortable light to carry and use. The button requires a firm press and has never activated by accident in the time I've had the light. Unscrewing the tailcap a quarter turn provides a mechanical lockout for those who want to be sure.

Modification potential

I've decided to start including modifications in reviews. Some people just can't leave well enough alone, and I'm one of them.

This Prime, having a 12V emitter is limited in its emitter swap options. Other XHP35s would work. With a different MCPCB and possibly a different TIR optic, 12V versions of the XHP50, XHP50.2 and Nichia 144A would work. TIRs with different beam characteristics are available and could be installed without much difficulty. I can't imagine wanting to change anything about the driver.

Getting to these components requires removing the bezel though, and it's screwed in very tight. There's not much to grip from the outside. I tried a strap wrench without success. There are three divots in the bezel, and a custom tool, or possibly an adjustable pin spanner wrench could be used to unscrew it. I eventually used vice grips, which slightly marred the finish.

Emitter swaps are somewhat difficult as the MCPCB is held down with rivets. If the rivets are drilled out, I recommend using thermal glue rather than non-adhesive paste to hold down the MCPCB.

This BLF post has information on problems with the factory optic. It wastes about 40% of the light, resulting in huge improvements from using a Yajiamei optic appropriate for the LED.