Minimag LED multimode runtime (my first runtime test)

So I finally got my $20 amazon light meter (by Mastech). I was planning on getting a good one, probably an extech data logger, but I'm short on cash at the moment. I'm mainly interested in testing lights that don't have runtime graphs that I can find.

For this test, I manually checked the meter every 10 minutes because I didn't want to be running in there every minute or 5 minutes. This allowed me to study in between readings.

Since these are runtime tests, I'm most interested in relative values. The measurements are in lux, but all I'm doing is aiming the flashlight at the meter, at a distance of ~10cm under a meter, in a dark closet. I have not made a light box, and due to how I'm doing these tests and with the cheap meter I'm using, I dont expect the lux values to be accurate. With that said, if I test a light that has a known lux value that somebody with better equipment has found (or the manufacturer), I can adjust the test to get an initial value close to that.

So...Minimag LED multimode. My initial lux values were high, almost 3200 when the 1m value attained by the manufacturer is 2547. The ANSI standards to state that that measurement is taken after 30 seconds and mine was initial, but even after 10 minutes, I was at 2800.

The real puzzle to me is that the light didn't last anywhere near the claimed 18 hours to 10% output. Even if I start at the 10 minute lux value (to account for the fact that I didn't measure at 30 seconds), and even if I account for the fact that I'm approximating when 10% output occured (No measurement taken between 10 and 18 hours - sleeping), it isn't close. 10% output occured at around 670 minutes (11 hours) on fresh Duracell batteries.

So why did this happen?
The meter is cheap, but this can't account for more than a small error.
My testing site (light on a shelf in a dark closet) is certainly not as good as a light box, but this shouldn't affect relative measurements of lux (If I was trying to test overall output, this setup would not work at all...).

Let me know if you have any ideas on why this large discrepancy occured.

It could be because you were using alkaline batteries. Lithium batteries have better regulation for high-drain devices, such as flashlights and cameras.

even for alkalines, it seems to have very poor regulation

enomosiki said:

It could be because you were using alkaline batteries. Lithium batteries have better regulation for high-drain devices, such as flashlights and cameras.

Click to expand...

I agree, but maglites are designed to use alkalines, and I'm sure their ANSI standard runtime test of 18 hours used alkaline. For other, high-power lights, I'll use eneloops as well as alkalines/lithium.

makes me almost wonder if you have a defective light, because the only time I have seen a regulation like that on a maglite is with their incandescent models

Here's a run with Duraloops. You can see flatter (but not flat) regulation, but with much reduced overall runtime compared to alkaline.

upriver, thanks for the test. It looks like there is some regulation on NiMh cells but I wonder if that is just the way the duraloop discharges. It does not look like there is any regulation at all when using alkaline cells.

tre said:

upriver, thanks for the test. It looks like there is some regulation on NiMh cells but I wonder if that is just the way the duraloop discharges. It does not look like there is any regulation at all when using alkaline cells.

Click to expand...

Doesn't look to me like there's any regulation at all. What you see with NiMh is the fact that once they get down to something like 1.15-1.2V they will hold that voltage steady for a long time until they get depleted and then they fall down quickly.

Alkalines just go down continuously without any plateau.

Nap.

to Upriver --

When you removed the exhausted Duracell Alkalines,
did you measure their (open circuit) voltage ? ? ?

Been my experience (with Alkalines),
that one cell in the "battery" often goes Belly-Up (near dead),
while the other cell(s) were still maintaining a nice, steady decrease.

Thereby causing such a massive voltage drop, the run-time test is effectively OVER.

I've seen this happen LOTS of times.
Regardless of brand name.

Even when i would carefully check each cell BEFORE use.


That would be my hunch.


Hope this is helpful.

Thank you for doing this test.
We appreciate your efforts.

But, hey -- stay AWAKE next time ! ! !

:wave:
_

I don't buy mini mags anymore because of this here http://www.candlepowerforums.com/vb/showthread.php?316946-MiniMag-LED-unreliability-problem-solved

But this regulation chart suprises me, from using the mini mag rebel I would have though just from experience the regulation would have been more solid, very suprising.