*Another runtime test with 27LT-S* UPDATE

[Strauss]

Well, I just got done testing my 27LT-S on high with AW protected RCR123 750 cells. On two different sets of batteries, I got just a little over 1hr. of runtime on high, then the light just shut off.

When I tested a 17670 cell, I got a ton more runtime, although it wasn't regulated. I figure I got a good 2.5hrs. of bright light with the bigger cell.

Does this sound about right for the RCR123 cells? Has anyone else tested their light(or even a luxIII or luxV for that matter) on high with RCR123's? I kinda expected closer to 2hrs, thats why I did the test twice with the same results both times. Any more info would be greatly appreciated.

 

[PoliceScannerMan]

Re: Another runtime test with 27LT-S

When I tested a 17670 cell, I got a ton more runtime, although it wasn't regulated. I figure I got a good 2.5hrs. of bright light with the bigger cell.

Why isnt it regulated with the 17670? Not enough voltage?

 

[Bob_G]

Re: Another runtime test with 27LT-S

I think it's pretty much accepted that RCR123 cells are over-rated capacity wise, where the larger cells are fairly accurate. If those are the original AW cells, I think 400mAH is about what you get, so your times make perfect sense - twice the capacity equals twice the runtime. AW's new high current cells are supposed to be better all around, but I'm not clear if capacity is actually any better.

PSM - With a DB917, and figuring voltage sag, a fresh 17670 would be right on the edge of DD wouldn't it? If in regulation, it wouldn't be for long I'd think.

 

[Strauss]

Re: Another runtime test with 27LT-S

I will have to check with my light meter. It may have stayed in regulation for a bit, but for sure not that long.

 

[Strauss]

Well, I just did a quick test with my light meter(Extech 403125) on the 27LT-S. I set-up my meter for lux measurement, and popped in a fresh 17670 cell from AW.

At the start, after being on for about 45sec., I got the light in the position I wanted it and took my first reading. Here are my results(FYI on 2 RCR123's I got 4,500lux):

Start: 4150lux
10min: 3950
20min: 3700
30min: 3500
40min: 3200
50min: 3050
1hour: 2900

So, it appears that my eyes did not lie No regulation with the 17670 cell, with the trade off being a good 2.5-3hrs. of light brighter than the low setting.

Now I know Yaesumofo meter'd 5,500lux I believe with his 27LT-S, which had me suspicious when I only could get 4,500 out of mine. So, to test my meter set-up, I threw the A2 on and got my usual 2,400lux. So either he has a "special" 27LT-S, or I have a dud :thumbsdow If anyone else has taken a lux mesurement I would love to see it, thanks a bunch!

 

[Rudi]

Consider that in an a-b comparison of brightness, the eye can barely distinguish a 20% difference, so Strauss' and Yaesumofo's lights aren't that far appart. My own 27LT-S falls exactly in between, at just under 5,000 lux.

 

[jki]

I am wondering if the gradual decline in intensity is due to the LED efficiency dropping off as its junction temperature rises with the flashlight heating up? Even if the regulator is maintaining constant current, if the junction temperature rises, the electron-to-photon conversion efficiency of the LED will decrease with increasing temperature resulting in decreasing intensity.

 

[Rudi]

Could well be. My PD-S on high in free air gradually dims by about 30%. If I then hold it in hand, it ragains most of the lost brightness within two or three minutes.