Runtime of my light

Hey all, I have this light

http://www.brightguy.com/products/DeWALT_1AA_LED_Flashlight_DPGA-1AAT.php

It works pretty good for my purposes. Its rated at 66 lumens and it seems to provide that. My problem is its rated for two hours of runtime and I'm lucky if I can get an hour out of it. I always use fresh Eneloops. Any ideas?

Run time: Not rated. According to the specs.

Well, let's see: the LED is apparently driven at 350 mA, and the datasheet for the XR-E gives a typical Vf of 3.3 V at that current. So assuming no losses in the driver, the current drawn from the battery would be:

Ibat = 3.3/1.2x350 = 960 mA

Now an eneloop has a capacity of 1900 mA, so the maximum run time possibly achievable would be:

Tmax = 1900/960 = 1.98 hours

That's close to 2, but you have to take efficiency into account since no driver is perfectly efficient. So more likely we would expect 1.5 hours. If you can't even get that it means the light is poorly designed or it means your eneloops are in bad shape.

For a comparison test, how long does the light run on an Energizer Lithium cell?

You may find that the run time quoted by the manufacturer is for the best case scenario of using a battery with the largest available capacity.

Yer' 2-hour runtime rating musta' been

by the same fine folks who claimed that

my car would get 25 miles per gallon.






(of course, YMMV)




Just where did you see that "2-hour" rating listed ?

Didn't see it on BrightGuy's website.



Did it specify "Sanyo Eneloop" ? ? ?

(or any specific battery ?)



Otherwise, you can "assume" they mean "Energizer L91 Lithium cells".

_

Burgess said:

Yer' 2-hour runtime rating musta' been

by the same fine folks who claimed that

my car would get 25 miles per gallon.






(of course, YMMV)




Just where did you see that "2-hour" rating listed ?

Didn't see it on BrightGuy's website.



Did it specify "Sanyo Eneloop" ? ? ?

(or any specific battery ?)



Otherwise, you can "assume" they mean "Energizer L91 Lithium cells".

_

Click to expand...

The two hours was either in the spec from my link or from the Amazon description. I just checked both and its not there now. Maybe they realized that if didn't perform at that level. I do remember that it just said two hours without specifying the type of battery. I don't even think I get an hour out of it. I've been trying to find a single mode, forward clickie, around 60 lumens, single AA light and its not easy. Besides the short runtime its also a reverse clickie. :thumbsdow

You can set the NDI or D10 to ~60lm and leave it as a single mode light. NDI is forward clicky, D10 does have a forward momentary function.

sweetlight said:

The two hours was either in the spec from my link or from the Amazon description. I just checked both and its not there now. Maybe they realized that if didn't perform at that level. I do remember that it just said two hours without specifying the type of battery. I don't even think I get an hour out of it. I've been trying to find a single mode, forward clickie, around 60 lumens, single AA light and its not easy. Besides the short runtime its also a reverse clickie. :thumbsdow

Click to expand...

When they didn't specify the type of clickie, you should assume that's reverse clickie. When they just said XR-E without specifying what LED, it probabaly is the lowest bin LED.

Getting 60 lumens with little more than an hour shouldn't be that difficulit, but some manufactures know how to screw up on that.

For "a single mode, forward clickie, around 60 lumens, single AA light " there're lots of AA lights available when you don't mind reverse clickie. And some dealers sell forward clickie switch, so you may swap it out with the one come with the light if you want.

Mr Happy said:

You may find that the run time quoted by the manufacturer is for the best case scenario of using a battery with the largest available capacity.

Click to expand...

or till death, like surefire...right at zero all the time now...

Marduke said:

You can set the NDI or D10 to ~60lm and leave it as a single mode light. NDI is forward clicky, D10 does have a forward momentary function.

Click to expand...

I almost pulled the trigger on the D10, but I really just want a single mode, no fancy features that might break or complicate matters light. I figure someone will make it eventually. The Energizer with the Cree I got is nice, but only about 35 lumens.