First, I want to discuss a few things about these lights regarding their output/runtime profiles.
I took both lights and ran them for 5 minutes, rested them for 5, ran them for five, until they ceased to function (shut off completely). Both lights showed less and less output as the cycles went on, and physically began running noticeably "cooler" after about cycle #3, as well as dimmer. Both lights shut off at around 3 resting volts, so as to preserve battery integrity. Fully charged Keeppower 18350 unprotected batteries were used in both.
Both lights appear to use "direct drive" type setups, more or less, that is not fully dependent on thermal management, but rather, as the battery wears down, so does your output.
The modlite performed without indication of power reduction (minus visual signature) until shortly after the 5 minute cycle comprising it's 20-25 minute run-time segment began, whereupon it blinked a couple of times and then continued. It did this again on the 25-30 minute segment, whereupon it then did the same at around 27 minutes and dimmed to what would be, for this light, "moon mode". Still pretty potent by 2005 standards, though. At 30 minutes, it blinked and dimmed even further, and at this point began blinking every 15 seconds or so until the light completely shut off at around the 31 minute mark.
The REIN seemed (as best I can tell without an integrated sphere), to follow similar output reductions at similar times as the modlite. However, it did not have any "blink warnings" programmed into it. It simply shut itself off at 28 minutes, was promptly restarted and ran until 30 minutes when it was shut off, and then upon being restarted shut itself back off at around 31 minutes.
I took photos of the beams at about one minute runtime or so outside, centering them on my gazebo at approximately 75 yards. I then took photos of the beams after 31 minutes each on the same gazebo at the same distance. These photos were a product of rapidly photographing the beam as soon as I switched the lights on, as they only produced the level of light pictured VERY briefly (5 seconds at most), and then either shut off, or went into a mode suitable only for looking for snakes where you are about to step before then very quickly/soon after shutting off.
Following this, to test the hypothesis that these use a direct drive type input/output scheme of some sort, independent of the units heat, I let both lights cool to room temperature, and then tested them each with a battery having 3.6v resting, which is about 5% battery capacity, but which is well above the cutoff point for either light. The results of that is also pictured.
I also performed a "20 minute all-out" runtime test. The lights were switched on and a timer was set for 20 minutes. Again, fully charged Keeppower 18350 unprotected cells were used. The battery voltage was immediately measured upon completion of the test. The modlite went the full 20 minutes, gradually reducing output, and the battery measured 3.55v immediately after, under no load. The REIN Micro on both occasions I tested it (to verify first test's results) went about 18-19 minutes stepping down gradually, before going into a pretty notably low mode. The first time, the battery measured 3.15v, and the second, 3.12v. The one difference is that I used the Modlite tail cap for this vs the Surefire DS00. This is a potential variable for the modlite.
My theory is that the REIN has a heavier bezel/head. It weighs 3.0oz, while the modlite head weighs 2.2oz (This is the new "slim" profile). I believe that the REIN runs "harder" for longer because the thermal mass of the head is greater, allowing longer runtime before reducing output for thermal management. I cannot prove this as I do not have a light box or integrated sphere, but it is my presumption based on the lights performing so similarly when run for 5 minutes, and shut off for 5 minutes, but now showing some disparity. It is notable, however, that at 3.6v resting, a rechargeable battery has only an estimated 5% of its capacity remaining, so the difference is not as great as one might first appreciate between 3.15 and 3.55 volts on the resting battery.
Further, I have a video that I am uploading, the link to which is provided, but it is not live at this time, it should be later today, however.
REIN Micro with new battery:
PLHV2 18350 with a new battery:
REIN micro after @31 minutes of runtime, instant-on:
PLHv2 18350 after @31 minutes of runtime, instant-on:
REIN Micro, 3.6v battery (5% capacity remaining):
PLHv2 18350 after 3.6v battery (5% capacity remaining):
Video comparison and more yammering and conjecture from yours truly:
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