Black Diamond Zenix IQ vs. Princeton Tec Yukon HL

[Bob Gabbart]

Any thoughts on these two headhamps for winter travel? Does the Yukon have current regulartion? How do the burn times compare? Brightness, beam pattern?

[Rick Dreher]

Hi Bob,

I’ve unfortunately not had a look at the HL but did spend a good deal of time testing the IQ.

It appears that the HL isn’t regulated. Although the Princeton Tec Website is silent on the topic REI notes it is not and I’ll believe them unless contradicted by PT or somebody’s teardown test.

Because the Yukon has a fairly large traditional reflector in comparison to the Zenix’s collimator, I’ll venture that it’s got better beam control (I’ll happily defer to anybody who’s seen them side by side).

The Yukon is waterproof while the Zenix is water-resistant–a bigger factor in rain than in the snow. The Yukon will certainly get more life out of its three AAs than the Zenix does out of two, with the obvious tradeoff of greater weight and bulk. I think it’s worth noting that the Zenix is very compact for a headlamp with a remote battery pack and will take up less pack space. It will also be less noticable when being worn.

The Zenix IQ, even carying a spare battery set, weighs a good deal less than the Yukon HL and should be equally useful in the field, which would probably tilt my choice to the Black Diamond. It’s also cheaper and has a battery meter.

Either light will take lithium cells, which will help both cold-weather performance and promote steady output from the Yukon despite the lack of regulation.

I’m in the midst of testing the Petzl Myo XP, which weighs less than the Yukon, also takes three AAs and features a brighter 3-watt LED. It also lacks regulation but avoids the complexity of extra LEDs for floodlighting through a diffuser lens. If you’re thinking about a larger headlamp like the Yukon, give it a look as well.

[Bob Gabbart]

I just checked out the videos on the REI website of the Petzl Myo XP. Looks sweet. I’m not in a hurry to get a new light so I guess I’ll wait for your review to make a decision.

Bob

[kevin davidson]

Bob—you might check out this review from the web’s resident light guru–
http://www.flashlightreviews.com/reviews/petzl_myoxp.htm

and contrast it with one for the Princeton Tec EOS
http://www.flashlightreviews.com/reviews/princetontec_eos.htm

good luck

[Richard Nelridge]

Bob,

If you are interested in a slightly smaller and lighter version of the Petzyl Myo XP, consider the Petzyl Tikka XP.

Rich

[paul johnson]

Good suggestion from Richard.

[Now for a collection of just somewhat related rambling thoughts, making no claim to “Pulitzer” quality writing.]

Just keep in mind that we don’t get something for nothing. In this case the weight savings brings both a lt. o.p. (light output) penalty and a battery life penalty. These trade-offs may or may not be worth it, depending upon how you use your headlamp.

The TikkaXP doesn’t seem as bright as the MyoXP. What I mean is, that I need to use the TikkaXP on HIGH in order to put out what appears to be similar light output to the MyoXP on MEDIUM. The same could be said for MEDIUM vs. LOW settings of these two headlamps, respectively. This is purely a subjective, qualitative statement. Don’t own a LUX meter. A light meter doesn’t really tell the whole story, but is frequently a good, rough gauge of how well two lights might compare side-by-side. To give those reading a better understanding of how I perceive light (it’s “downhill” to 100 for me – a bit more on age & low light vision later), i find that for distance viewing, not close up work where a large percentage of the light is reflected back to the eye) a 25% diff. in lt. o.p. is barely/somewhat noticeable, whereas a 33% diff is quite noticeable, and a 50% diff is dramatically noticeable. Compare this to your own perception of light differences to further gauge how well my comments might be applied to your own individual case.

For me, the MyoXP has recently replaced the Yukon HL as my headlamp-of-choice. Saves an ounce or two in weight. Has the boost mode which I use occasionally (BOOST – puts out a TREMENDOUS amount of light – in some ways rivals Xe lamp o.p., but in a smaller/narrower “spot”, so have to move head around more to pick out objects/blazes far away since can’t focus beam into a “flood”). i, personally, don’t feel that the “flip-up” diffuser on the XP’s is quite as good as a focusable halogen/Xenon beam for solving this and other issues – but, it sure is great when using either XP on LOW for close-at-hand tasks. in fact, for me, it’s a must, or the “spot” would be too blinding, even on LO if using either XP for task lighting.

Of course, later this month (unless its intro is pushed back again), the PT Apex may end up replacing the MyoXP. Yes…it’s gonna’ be heavier, but for the two hours to several hours of nighttime/wee hours of the mornin’ hiking I typically do, I will splurge and carry 2-4 extra ounces. The 4AA of the Apex vs 3AA of the MyoXP should provide greater batt life.

This last point, I feel from using a headlamp nearly every time out (if i’m solo – which i usually am), is important. Mfr’s batt life estimates are WAY OFF. Look…here’s what I’m thinking…. [if anyone feels i’m wrong on any or all points, feel free to set me straight.]

I don’t mind them, but I’m NOT the biggest fan of the one-headlamp-can-do-it-all philosophy, especially when there are two or three very excellent choices for task/proximity lighting. If I want to perform camp tasks, I use a Photon Microlight or PT Eclipse/Impulse (or Scout). This is generally all the light one needs. Sometimes, i may use a very kludgy, but sophisticated, home-made job (at a bit over 1oz, this 4 white LED microprocessor controlled “headlamp” employing PWM (pulse-width-modulation) with 1/8″ bungee head-band; powered by 2 3volt CR2032 batts in series with 16 dimmable lightout settings (1/4oz for head-band, 1/4oz for 2 CR2032 batts, ~0.5oz for the electronics & green “racer’s” (duct) tape encapsulating the circuit board). On some trails, I can hike on this home-made unit on HIGHEST output for at most 30min b/f the batts start to give up the ghost (~3hrs total “burn” time on HIGHEST o.p., but many, many more hours when set on the more dim settings and used just for task lighting). It’s sorta’ similar to the 4LED TikkaPlus when both are on HI. I don’t feel that i can hike using the other aforementioned task lights (the Scout on HI o.p. being an exception – at least for a short time on fresh batts). At lower lt. o.p. settings the home-made unit is fine for task/proximity lighting when performing camp chores. Perhaps, the closest off the shelf equivalent would be the PT Scout – a very fine headlamp indeed. Replace the head strap with 1/8″ bungee & save ~0.65oz, or dispense with the headband altogether & clip it to your hat, hat brim, belt, or pack strap – it only weighs ~1oz w/o the head band, IIRC (“if i recall correctly”).

But for nightime navigation on an unfamiliar, indistinct, leaf covered trail, searching for faded, low contrast blazes on a moonless/starless night/morning so no wrong turn is made, a real “man’s” headlamp is required. To this end these headlamps, IMHO, can be used for only 1/4 to 1/2 of the Mfr’s stated times – particularly if unregulated circuits. [Note: in my experience, regulated circuits only keep the lt. o.p. constant for a certain period of time – they DON’T increase the overall “burn” time, or even the time to 50%-25% output – the fact that regulator circuits consume some energy, with more or less efficiency, depending upon their design, means that they CAN’T increase overall “burn” time.] On alkaline batts (in warmer weather), the typical headlamp is down to only ~1/2 of the initial light output in only ~1/4 of the Mfr’s stated “burn” time (this is just a very rough approx. observation on my part; some differ somewhat, but usually not too, too much). Just peruse “burn” time graphs or tables of light output over time and this fact will also become apparent. Regulation obscures this somewhat, but then regulators, generally don’t function well as batt voltage drops below a certain design threshold (hence PT’s excellent regulated-then-unregulated-as-batt-voltage-drops design of the Eos and Corona). The HL, and two XPs (and several others) headlamp typically, for my use, stop being useful for nightime navigation when their light output drops to somewhere between 50% and 25% of their initial light output – usually closer to 25% depending upon initial lt. o.p. So, as a rule of thumb, i figure, 1/4 to 1/2 of the Mfr’s stated “burn” times as usable navigation light output. Also, I find that generally MEDIUM setting on these 1W and 3W Luxeon LED, or a Black Diamond/PrincetonTec Xenon main bulb headlamp is good enough for navigation, with occasional use of HIGH (or BOOST in the two Petzls). However, on MEDIUM, that additional “margin” of reduced lt. o.p. no longer exists as the batteries drain, i.e. one-half lt. o.p. of MEDIUM is usually too dim for me to navigate by. The Mfr “burn” times typically include how long can you use a “gigantic” (relatively speaking – cp. to a Microlight) 6oz to 10oz headlamp for in-camp chores, i.e. task/proximity lighting. The real time that these headlamps provide sufficient light output for hiking is far, far less. Who wants to figure “burn” times for a headlamp of this size based upon how long in-camp chores can be performed? Generally, one or two 0.5oz single LED microlights work fine for in-camp chores. The only reason an UL backpacker, IMHO, would carry one of these larger headlamps is for emergency evac, navigation or searching for something. But…then I could be wrong here. It’s just my opinion.

For extended, very high output “burn” times, giving the state of existing technology (which is only improving), for both Xe and LED and various types of regulation circuits and both the LED and electronics “substrate” materials, for really long “burn” times before lt. o.p. starts to perceivably diminish, then one must resort to larger batteries, e.g. 4C cell power sources, or other power sources used by “Cavers” – they sure do know lights (for obvious reasons). These, however are going to be 16+oz in weight for headlamp & batteries. I’m NOT advocating these units, though I have carried and informly field “tested” several (one-at-a-time) “Caver” (or SAR) type of headlamps. It’s just that, for me, I would be cutting it close (to my admittedly arbitrary 50% “rule”) to get through a 10+ hr nighttime emergency evac (like, when does that ever happen?) on the smaller, lighter (6oz to 10oz) headlamps i usually carry – IF they are run on HIGH output the entire time (HI o.p. vs. MED o.p. – maybe need more light in an emergency???). Of course, 3-4 AA or AAA spares, as req’d by the headlamp, could always be carried – even more, when cp. to the weight of these “Caver” 4C type of headlamps . [NOTE: some “Cavers” carry “rechargeable” NiCd or NiMh units (plus two backup lt. sources & spare bulbs – all for obvious reasons, i.e. the sun rises in a cave) – up to 52oz just for the batt(s) – so 16-24oz total weight for 4C powered headlamps would seem lightweight to them.] Also, having just made the prev. statement on 4C “burn” times, i do feel that some of the recent 1W and 3W (there are even 4W multi-LED units and at least one “5W-atter” out there, e.g., Speleo Technics Nova5) LuxeonStar type of headlamps makes this statement somewhat untrue. Time and technology will only make my statement even more false.

Keep in mind that light perception is very individual and what one person deems a sufficient amount of light to hike by, another person will deem insufficient. Low light vision is affected by various factors such as: age (worsens with age), smoker/non-smoker, certain medications, state of nutrition (of special importance to long distance hikers – think vitamin supplements and fresh veggies), genetics, and psychology (some people just feel like they need more light). All of these factors come into play – in combination. Also, less light is needed on familiar trails vs. unfamiliar trails even on cloudy, moonless/starless nights under heavy tree cover.

[Bob Gabbart]

Concerning the EOS, I guess I wanted to add that I’ll be using this light for winter navigation, so I wanted to get a light with a separate battery pack that would be kept under my hood. But I’ll definitely check out those other lights you mentioned.

[kevin davidson]

Lithium batteries( which will work in all units being discussed) make separate battery packs all but redundant. Not really effected by cold temps. I never use anything but for Winter use.
Packs are good for long term lighting needs–for example, caving, if they allow greater battery capacity. Cords and weight can get in the way.

[paul johnson]

Kevin’s right on. other reasons occasionally cited for rear-mounted, or belt/pocket mounted batt compartment are “balance” and weight on the head. however, how heavy can 3AAA Li batts be? answer: ~0.81oz (~1.2oz for 3AAA alkaline batts). “balance” might be more of an issue for older, larger halogen headlamps with larger reflectors.

[Richard Nelridge]

3 Li AAA batteries for my Petzyl Tikka XP only weigh about .8 oz. Therefore, subsituting the Li batteries for the AAA Alkalines for this light lessens the weight of the stock Petzyl Tikka XP by about .4 oz. Adding an extra set of Li batteries adds an extra .4 oz over the stock Tikka XP with a substantial amount of battery power and a bit less weight (and substantially more battery life) than its big brother with the rear battery pack.

Rich

[paul johnson]

Richard,

is it that much more battery life? maybe. i don’t know. you’re probably right, but i don’t know that it’s really that much more. why? when i read your comments two thoughts came to mind. i could be all wrong here, so think about it and let me know.

[Any EE or battery engineer or battery chemist out there, help us out here, please.]

first (though this may be only a theoretical debatable point not really affecting practical use very much, since both XP’s are no slouches in the light output department): MyoXP is a 3W max output, whereas (i hope i’m recalling correctly here), the TikkaXP is a 1W max system. So, generally speaking, one can get away with a lower, longer “burn” time setting on the MyoXP and still put out the same amount of light output (see this point in a bit more detail in my prev. very lengthy post). we’d have to compare two graphs of light output vs time to see if this is true. at the very least, if it’s ever needed, the MyoXP can put out more light than the TikkaXP.

second: the total energy stored in the 6 AAA Li batts is 6 x 1350 ma-h (might only be 1250ma-h per cell, i can’t recall) = 8100 ma-h. whereas, the total energy stored in the 3 AA Li batts is 3 x 2850ma-h (might be 2950ma-h, i also forget this number – some hi-perf. alk. AA have 2950ma-h) = 8550ma-h. so, the 3AA Li batts have more energy than 6AAA Li batts. on top of this, each set of batts is really only good down to somewhere between 0.8 to 1.0 volts per cell. at which point, the combined voltage is too low to forward bias the Luxeon LED. let’s assume, (i don’t know for sure) this “wasted”/residual energy is approx. the same in both cases (6AAA vs 3AA). however, i think that the sum of the 6AAA unusable residual energy might be more than the 3AA batts residual energy. nah…i take that back (thinking “out loud”, so to speak, here). the 3AA will probably have a tad more residual energy left since they also had a tad more combined stored energy at the start when “fresh”/unused. this residual energy will reduce the AA stored energy advantage somwhat – like, maybe, roughly 1/2 of the delta b/t the two values calculated above (the amt. of residual energy would depend upon what the lower voltage limit is to fwd. bias the LED). i need to think on this last point of residual energy a bit more as i’m getting myself confused here as i consider various principles, albeit simple electrical principles, at work here. however, having said this, i must confess that i really don’t know very much about batteries (i know, i know…it shows, but just in case, i didn’t want anyone thinking that i’m some sort of expert on batteries).

there are other issues with smaller volume batteries vs. larger volume batteries – in this case AAA vs. AA. as current is drawn from the battery, it heats up due to the friction of the electrons flowing (or “holes” flowing???, if you prefer). the current draw might be the same in both instances – IF light output is similar. my guess is that the larger battery will both heat up slower, as well as dissipate heat better, resulting in better longer term/use battery performance as less voltage will be dropped inside the battery due to the battery’s internal resistance (which, my understanding is that it, goes up as the batt heats up). this is important to both regulated and unregulated circuits – though the effect will be noticed sooner in unregulated circuits, like those employed by the two XPs. this is why “Cavers” will periodically (sometimes every 30minutes, e.g. 30on, 10off – remember they typically carry three light sources – at least two of them high power sources & the third smaller & lighter) turn their lights off to allow the batteries to cool. if anyone has a BD ZenixIQ, they can easily see this effect. i tried this just last week. when a set of batteries is used to the point that the ZenixIQ doesn’t want to remain in 1W Luxeon HIGH output mode even after cycling through the settings (initially it will “jump” down to MEDIUM output, but cycling it back around to HIGH will temporarily restore HIGH output) and returning to HIGH mode (a simple trick to get more HIGH mode time out of the ZenixIQ on an existing set of batteries – this effect begins to occur at ~1.25volts left per cell in my experience – a pretty high voltage still remaining in each cell – sorry, don’t know the specifics of the ZenixIQ’s “buck” converter, or analogous voltage “step-up” circuitry, so i can’t explain why this occurs at such a seemingly high voltage.). after a while this cycling doesn’t produce any appreciable return to HIGH mode. then, in this case, turn the ZenixIQ off & let the batteries cool. 5-15 minutes later, you can switch it back on & get more 1W Luxeon HIGH output mode – at least for a little while longer.

oh…got a bit off track with the ZenixIQ info (it would apply, in some fashion, to any headlamp, however)…so back to this last prev. point: the AA’s will heat up slower than the AAA’s & provide better long term use since they will be more efficient when used this way since less energy is converted to heat inside of the battery as compared to the AAA batts. What do you think?==> for high current drain applications, or continuous use of HIGH-type modes, maybe we don’t want to keep the batteries as warm as possible inside of our insulated jacket? perhaps, it’s better to maintain a more moderate temp (i.e. not too hot & not too cold – esp. for alk. batts) for optimal performance?

just keep in mind, that this last point on “heat” amounts to merely, seemingly logical musings on my part, based upon some actual physical and electrical principles at work in battery powered devices. as such, they should not be taken as gospel. again, i know very little, for sure, about batteries. also, as UL backpackers we don’t want to carry two higher power “navigational” headlamps so that we can let one “rest”; we could swap batts in & out to let a set cool, but this would be more trouble than it’s, perhaps, worth.

oh…BTW, the 6 AAA Li will cost ~2x the cost of 3 AA Li batts.

[Richard Nelridge]

Paul,

I am probably incorrect regarding battery life (but I am not sure if that would apply to the MyoXP at its maximum of 3 watts and the Tikka XP at 1 watt); you are probably correct regarding this. Also, no question that 2 sets of AAA Li batteries will be substantially more expensive than a single set of AA Li batteries. Also, no question that the MyoXP has more output at maximum of 3 watts versus 1 watt for the Tikka XP.

But for size and weight, the Tikka XP has an advantage, and even in cold conditions, wouldn’t the 1 watt output (particularly with snow as a reflector) be adequate much of the time. Additionally, wouldn’t a second set of Li batteries be sufficient for a 3 or 4 outing? Also, as the batteries get colder even Li batteries (I suspect) will not perform as well as in warmer conditions. A second set of batteries would allow for rotation of 1 set for another.

Rich

[paul johnson]

>>”But for size and weight, the Tikka XP has an advantage, and even in cold conditions, wouldn’t the 1 watt output (particularly with snow as a reflector) be adequate much of the time.

Absolutely right. Even without snow, i find the MEDIUM output on both the TikkaXP and Eos sufficient for hours of hiking.

>>”Additionally, wouldn’t a second set of Li batteries be sufficient for a 3 or 4 outing?”

Sure. You’re right again. I guess I get too theoretical/technical. Us Engineers like a safety margin, i guess. maybe this is just a euphemism for being a bit paranoid about some things.

>>”Also, as the batteries get colder even Li batteries (I suspect) will not perform as well as in warmer conditions.”

I’ve read that point elsewhere also, though it’s NOT normally mentioned regarding Li batts. I’d like to see a performance comparison of room temp, freezing, and 0F. i guess we don’t read much about this point since Li perform so much better than alk. batts in the cold.

>>”A second set of batteries would allow for rotation of 1 set for another.”

Sure, but i’m too lazy to do that. As well as the fact that I’m such a klutz: i’d probably drop them in the snow and lose them.

i hope that you understood, that i wasn’t saying your suggestion was wrong. actually, the TikkaXP and Eos are really fine for my needs. i’ve just gotten used to the larger Yukon HL & so opted for the MyoXP as a replacement (it’s really more than a “Whose got the biggest headlamp contest” – my masculinity is NOT measured by the size of my headlamp). i just like to have a headlamp that can reasonably go close to 10+ hours MEDIUM output without a battery change. no good rational for this requirement on my part. In fact, the Eos & maybe the TikkaXP come close to that arbitrary 10hr requirement of mine.

BTW, Richard, i was editing my prev. post while you were posting a reply to it. i’ve added more info to it that you might(???) find interesting.

[Rick Dreher]

I’ve come to feel that so long as the headlamp’s lightweight and the overall form is compact, then there’s little compelling reason to separate out the battery pack, other than for use in bitter cold conditions. OTOH lights that jut out farther, like my old PT Solo, are inherently less balanced and can be annoying to wear. They also tend to bounce more, especially if they don’t have a bucket-style strap.

A remote battery pack adds complexity and a cable but has the plusses of keeping the batteries warm with body heat and achieving balance of heavier lights. A detatchable pack with a longish cable can be tucked inside a coat and also allows for reading while lying on one’s back.

On temperature performance, when testing the Eos I found no performance difference between room temperature and refrigerated (at 35 degrees). It seemed that that the waste heat from the LED was helping warm the batteries in a sort of weird harmonious coexistance. The light never felt as cold as other items in the fridge when I took it out for periodic measurements. Not exactly scientific, but it was definitely happening. I don’t notice heatsinks being a requirement on headlamps with integrated battery packs.

–Rick

[paul johnson]

Mr. Dreher,

great headlamp reviews you wrote. really appreciate them.

can you please try the freezer (prob. 0-10 deg F) & let us know how the Eos does with Li batts?

>>”harmonious coexistance”

excellent observation and point. to wax philosophical for a moment, perhaps a lesson for life regarding “harmonious coexistance”
all of us can take to heart and learn from.

>>”heatsinks”

Corona/Apex has/will_have one. i have a “home brewed” single output mode (full blast) 1W Luxeon with collimating optics i put together recently (BTW, attached it to my old PT Solo headband & mounting plate) which uses a large aluminum heat sink (it came with the heatsink, so i used it). it’s a 6V system using a simple 3.3ohm current limiting resistor to keep it from burning up – so i guess i’m driving it at ~167ma. it gets a might on the hot side – probably will have a short LED life. as you know, lack of a heatsink is the reason for the timed-BOOST mode limitation in the two Petzl XP headlamps – heat is “anathema” to electronic devices – Si junctions break down at ~175deg C internal junction temp – IIRC (if i recall correctly). it can get mighty hot in them little junctions.

[kevin davidson]

more on batteries and low temps. can be found at–http://www.climber.org/gear/batteries.html#wilson

if this isn’t a compelling arguement for lithium batteries…

[paul johnson]

great link Kevin. thanks. appreciate it. just the type of info i was hoping for.

Mr. Dreher, guess you can skip the “freezer test”. thanks.

[Rick Dreher]

Thanks Paul, for your comments and pushing the experimental envelope :-) Would you say the Solo’s batteries are too isolated to perform any heatsink duties, or benefit from lamp heating? (Compared say, to the Aurora, Eos and Tikka which definitely could.)

I do appreciate the need for heatsinks and will note that the Speleo Nova heatsink actually gets HOT to the touch, not just wimpy warm :-)

The Myo XP has a quasi heatsink inside but I’m not convinced it’s not actually an RF shield, since it’s completely encapsulated in plastic.

re. 0 deg F freezer testing, without spousal approval I’m not sure I’m going to be tacklimg that one :-( I sometimes question whether 0 deg testing is even valid for headlamps, as compared to handheld flashlights. Maybe we need a team of wintertime travelers rigged up to tell us what their headlamp battery temps actually are? (Only half-joking here.)

–Rick

[paul johnson]

>>”Would you say the Solo’s batteries are too isolated to perform any heatsink duties, or benefit from lamp heating? (Compared say, to the Aurora, Eos and Tikka which definitely could.)”

too uninformed for me to venture a guess. any opinion i would put forth would be worth what it’s costing you, i.e. NOTHING.

>>”I do appreciate the need for heatsinks and will note that the Speleo Nova heatsink actually gets HOT to the touch, not just wimpy warm”

don’t own either the Nova3 or Nova5. can you give more info about them?

>>”The Myo XP has a quasi heatsink inside but I’m not convinced it’s not actually an RF shield, since it’s completely encapsulated in plastic.”

hi-temp plastic??? i don’t think that it’s a heatsink due to the plastic and from what i’ve read elsewhere, the MyoXP doesn’t have a heatsink.

>>re. 0 deg F freezer testing, without spousal approval I’m not sure I’m going to be tacklimg that one”

initally, i was going to warn you of this caveat (“husbands, don’t try this at home…”), but was selfish and really wanted an answer.

>>”I sometimes question whether 0 deg testing is even valid for headlamps, as compared to handheld flashlights.”

certainly NOT in Southern Connecticut, but i’ve seen morning daylight temps of -16 to -22 below 0 (actually temp w/o wind chill) in Maine, Vermont, and New Hampshire. now…i must ask myself, do i really want to be out in dark and cold testing headlamps…they don’t pay me enough!

[Bob Gabbart]

I was looking at the specs for the Zenix IQ (2 AA) and the Yukon HL (3 AA) and at 1 Watt full blast, the HL is rated at 44 hours and the IQ is rated at 8. How do you go from 8 hours to 44 hours with a single AA battery?

[paul johnson]

[the following is NOT intended to be overly technical. as much as possible technical details and terminology is avoided. just enough is given to help understand, on a basic level, the principles involved. as such, it won’t earn a very high grade in an Electrical Engineering course. those days are over for me anyways. so feel free to correct my simplistic explanations. i will enjoy reading them.]

[note: BTW, seen other published specs for HL as being only 25hrs on HIGH output.]

forget the specs. typically, those numbers indicate that there is still some light output – just enough to “see” (make out the faint outline) something in your pack 18″-24″ away (of course, “your mileage may vary”). others use some “cut-off”/minimal light output level, such as 1Lux or 2Lux of light output – both are very, very low light levels. you could NEVER use these high-powered 1W LED headlamps for navigating a trail when the number of hours on the batteries approaches these levels. typically, for navigational purposes, i figure 1/4 to 1/2 of the mfr stated time. if you haven’t done so already, please see that portion of my previous post that deals with this aspect. experience, with the headlamps i’ve used, has taught me this. this is a “rough” estimate. “your mileage may vary”. i believe i may have given some reasons as to why this variance amongst individuals exists in an earlier post.

one way to think about this extra battery is, that the batteries can never be fully drained by an LED application. at some point the voltage drops low enough that the LED cannot be forward biased (basically, this means that current will not be able to flow through the diode’s “junction” and produce any light). in most typical, current headlamp designs that i am familiar with, this voltage is typically 0.8 to 1.0 volts per cell. a typical high-perf alkaline 1.5v battery starts “life” at a bit over 1.6v. so, you can see that there will be much “residual” energy left in the battery in LED applications.

[note: don’t take this to mean that an incandescent headlamp can make use of this “residual” energy. if you put these “expended”/used batteries in a simple non-regulated incandescent headlamp, typically, the bulb’s filament might just “glow” dimly, not providing any sufficient amount of light, or for a short time produce a small amount of useful light for close at hand tasks. sure, the incandescent circuit will further drain the batteries, but it won’t be for any practical or significant use/purpose.]

with all semi-conductor devices, there is what is known as a “bias voltage” which is the minimum voltage required to “turn the device on”. it varies depending upon a number of factors, but basically, for the types of LEDs that we are speaking about it ranges, if i recall correctly – please check these numbers with a more reputable source, from about 2.4volts for longer wavelength LEDs to about 3.6volts for shorter wavelength LEDs (so-called 5mm “white” LEDs are typically about 3.4v or 3.5v). i’m only speaking here of LEDs that produce light in the visible spectrum; IR (infrared) and UV (ultra-violet) LEDs further extend this voltage range – if i recall correctly. i believe “white” Luxeon-type LEDs have a somewhat lower forward bias voltage than most “white” 5mm LEDs. however, we expect more light output from a 1W, for navigating, hence this point is perhaps not as practical as it might initially sound.

so, only a portion of a battery’s stored energy can be used. in the case of the ZenixIQ, a “buck” (voltage step-up) converter needs to be used to get the voltage from two batteries high enough to “turn on” the LEDs. this circuitry also has some small minor parasitic loss associated with it. since, no matter what particular circuit design is used in its (and any headlamp’s) converter /regulator it too will consume some energy in order to function. at some point the voltage in the two batteries is too low to be “stepped up” high enough to make the LEDs light up/turn on. BTW, any regulator will have some “parasitic” losses associated with it. a key aspect of DC-to-DC regulator design (the type used in battery powered devices) is designing the regulator to require as little energy as possible for its own operation, leaving as much energy available as possible for the LEDs.

when more batteries are used, the power supply circuitry in an LED circuit must somehow (a simple resistor, a voltage regulator, a constant current regulator, etc) make sure that the voltage actually being applied to the LED at any point in time NOT be too high, or the LED could “burn up” due to too much current flowing through it (current produces heat due to friction – heat is the real enemy of semiconductor devices, hence “burn up”). think of current as analogous to water flowing out of a faucet, and voltage as analogous to the pressure that forces the water out of the faucet. in this analogy, the batteries function as the remote pump/pumping station that produces the voltage/watet pressure. it’s as simple as that. more pressure = more water flow out of our faucet. more voltage applied = more current flow in our simple, unregulated LED circuit. (current limiting works a little different in a regulated circuit; let’s not get into that here as there are several basic regulator designs commonly seen in LED headlamps).

a regulator does not and cannot give longer battery life since it too requires some energy to function. what it does is hold light output level constant for some period of time. this is often a desireable feature. at the very least, it is psychologically comforting to have a constant level of light output.

if you look at it this way, with more batteries (or the same number of larger size batteries), there is more total/available energy available before the voltage gets too low. this is also why, i stated that the fourth battery in the upcoming PT Apex should provide longer batt life than the MyoXP – assuming similar light output levels. of course, the Apex will weigh a bit more than the MyoXP. it’s a trade-off.

more specifically, regarding your IQ vs HL question. my guess is that a smaller portion of the energy in each battery is “available” for the 1W LED in the IQ than in the HL due to the nature of a “buck”/voltage step-up converter. for example, on my ZenixIQ, the flashing “battery state” indicator went from GREEN to RED when the batteries were at approx. 1.25v. at this point, the IQ didn’t want to remain in HIGH ouput in the 1W mode. it wanted to only operate in MEDIUM (see my earlier post for more about this and how to get more HIGH output from batteries in this condition). Three batts in the HL at 1.25v will probably still produce a very high level of light output.

i’m going to end this post here while there are still some readers still awake (plus the Formula1 race from Suzuka Japan is starting very soon; don’t want miss the formation lap and start of the race). if you need more info, just post back and i’ll try to answer your question(s).

[paul johnson]

FYI,

just heard from the owner of BrightGuy.com (i have no affiliation with BG except as a loyal customer for a while now)

the PrincetonTec Apex has now arrived in retailers hands and available for purchase.

check with BrightGuy or your favorite web merchant/retail store. BackCountryGear (ask for Doron – you can tell him i told you to ask for him; Eric is good also) and BaseGear are two that also had them “pre-listed” on their website.

Please note, i’ve seen prices vary from “full retail” to ~20% below full price (even though it’s just being introduced) – so, you may want to shop around.

[Author]

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