a "regulated" question

gramps416

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Hello, I have a question about regulation on two different headlamps.
I am trying to decide to keep the petzl Myo xp I just bought, or to switch over to the myo Rxp or Princeton tec apex.

The deciding factor is battery life in regulated mode using NIMH batteries.
I know there is alot of data out there, but it is difficult to weed out the information for this question.

I am interested in both the low and high settings of the luxeon led for both of these lamps. (ignoring the apex 4led flood)

I don't know if I can justify keeping my current myp xp if the brightness dies down in a short time.

in addtion, I would also like to know where to buy an RXP if that is the choice? I read in a post that Mountain Equipment co-op wont carry it any time soon. Are there any physical stores in canada? Online is there any other stores than Brightguy? (relaiable online stores).
This company ships UPS and anyone who lives in canada and has shipped here knows the cross border issues with UPS.

thanks

-gramps416
 

kwieto

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But what kind of data do you need?

Both companies are presenting the data about running times (including the regulated period) for every mode, so it is easy to compare?
 

gramps416

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that is true, the the posted times are ideal,if you had a lithium battery.
The advertisement is like how the big three automakers advertise their fuel economy ratings.

the reality, is that I think a fair chunk of this market for headlamps would use rechargeables rather than a (one use) lithium battery (which the advertised times are based on)

I don't really care about Ideal conditions, real conditions is what matters, you are not going to use your headlamp when the amount light produced from it is useless for your application, you want to replace them.

Everyone is different, i think I am speaking for alot of others here, who would replace them at the most convenient time after the regulated time expires

-gramps416
 

jankj

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Good question! It's hard to sift through all the marketing hype to get all the nescesarry information from many manufacturers. Such as - that runtime quoted in the ad, was that with nimh or alikaline batteries? (Probably not litium, but you never know...)


Have you tried searching cpf for some reviews of those lights? There will probably be some comments on runtime, hopefully some runtime graphs as well..
 

gramps416

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I have sifted thoroughly through the forums, and I can see no chart comparison on NIMH run times for the RXP and XP. I found one for the original XP(version 1) but that was based on alkalines. I am not (will not ) be running anything other than NIMH.
does anyone have this sort of information?
-gramps416
 

yellow

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Mostly all better PTs had very stable regulation
(mostly same brightness for "shorter" time with a "sudden" decline at end of battery voltage),

while any Petzl (of which I have seen plots till now) showed more some kind of "direct drive behaviour".
No real direct drive (extreme reduction in output at beginning and then very slowly fading away), more some kind of "mix" between the extremes...
a constant decline in output over the full runtime, extending the time light is emitted.


In short:
Apex: same brightness for shorter time,
Petzl: dimishing brightness for longer runtime

(Pls note that this is a guess for that Petzl in question)
 

NoFair

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A PT Apex on AA NiMHs will run about 3-4 hours on high and drop in brightness after that.

It does not shut down and will give usable light at least 12 hours (forgot mine outside in the snow while it was on...:ohgeez:).

Sverre
 

jwellford

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Crazy, I'm just posted a thread with a similar question. FWIW, I think Petzl's data on the RXP was taken with NiMH batteries (at least that's how I interpret the row in their Performance Tables labeled "Batteries"). The XP says LR6/AA x3, while the RXP says NiMH.

Edit: Never mind, it clearly states in the tech notice that alkaline batteries were used in the test. I don't know what the "Performance table" meant when it said NiMH.
 
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gramps416

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interesting, you mention that. I wonder by how much that difference is. I can tell you this, my myo xp is still in the box it came in. It is difficult to compare apples and oranges :)
 

Alan B

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Using NiMH in the Myo XP produces a fairly well regulated output.

Comparing the manufacturer's runtimes directly is pretty meaningless. The testing is just not comparable. They often measure the highest output and then measure runtime until the light winks out, even though the light was pretty dim for a good part of the runtime. Assume the runtime is a lot less than the claim for good output.

Given that the best way to good runtime is to run at the lowest power level that does the job, the Myo RXP's capability to select from lots of levels (about 10) may be helpful. The extra choices make it likely you can find a power level that will do the job and use minimum power.

I'm not sure what you are going to be doing, but my experience with the Myo XP is that it lasts a long time on 3 eneloops. (note that the older XP is not recommended for NiMH unless you install a fuse, the newer ones come with a fuse already). The XP has a great diffuser that doesn't stick out when flipped either in or out of the beam. It is compact and comfortable and easily adjustable for angle. The headband does not have a crumbly foam pad under the light that makes a mess when it ages. I upgraded it with an SSC led and it is still going strong after years of use. A great headlamp!
 
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yellow

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The key to long runtime on these lights is to use the lowest level that will do the job. They are all fairly efficient and will drop in intensity as they drain. NiMH produce a more regulated light due to their power curve.
wrong, what You mean is in regard to direct drive, but its "regulation" what is asked for

basic example (with plots stolen from flashlightreviews):
regulated on top,
direct drive below.
red line is output
regulated lights keep that (relativley) stable als long as possible, while Voltage of cells gets down, then - at end of regulation - loose output quick.
Direct starts strong and immediately reduces considerably, but then "fades away" less slower

b0c5f9g7vc2y2xsay.jpg

see the XP is no real direct behaviour, but also no regulation like

PS: of course the plots are just taken for example purposes of the red line, NOT for a direct comparison of these lights!!!
 
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