Flashlight efficiency?

Hello All,<br><br>I am new to the forum and this is my first post.<br><br>If two different lights have the same emitter (CREE XP-G R5 as an example) and the same battery arrangement (2 - AA as an example), I would expect the lumens * run hours be comparable.  They typically are not, however.  As an example:<br><br><br>Jet Beam BA20: 270 lumens *1.75 hours = 472.5 lumenhours<br>Fenix LD20: 180 *2.26 hours = 406 lumenhours<br><br>I suppose these differences could be explained by any of the following:<ul><li>Difference in the electrical efficiency of the electronic drivers;</li><li>Difference in optical efficiency of the reflector/lens combination;</li><li>Difference in testing methods;</li><li>Difference in modes (I understand that the high setting on some lights intentionally reduces after a couple of minutes); or</li><li>Bad data (intentional or unintentional).</li></ul><br>What do you think the causes of these differences are?  Any info on this topic would be greatly appreciated.<br><br><br><br><br>

ScottsoSmith said:

472.5 lumenhours
406 lumenhours

Click to expand...

So, 440 +/- 34 lumenhours. Is this +/- 8% spread statistically significant?

Welcome to CPF!

The difference is a combination of all the things you mentioned, ie driver, reflectors, methods used, etc..
It is best to see real first hand results of both lights.
Here is a great review of the BA20 and it has a comparison with the Fenix LD20.

http://www.candlepowerforums.com/vb/showthread.php?312793

Also it was hard to read your post, you have lots of weird character like "</li></ul><br>"

This was just one example. The spread quite often is larger. Take a look at the Nitecore IFD2 - 260 Lumens x .67 hours = 174 lumenhours.

Sorry about the odd characters - don't know why that happened.

Thank you for the reference to the very thorough review - quite helpful.

I read your post just fine, but I've been doing way too much HTML lately.

All the reasons you mentioned have an impact, with my personal experience being driver effieciency and output curve (flat versus tapered) are the most important.

The reviews from selfbuilt in the Flashlight Reviews section have been more helpful to me than any manufacturer's specifications. His runtime charts are great. Zebralight and Fenix are often efficiency leaders (though I happen to be a Malkoff fan myself).

ScottsoSmith said:

This was just one example. The spread quite often is larger. Take a look at the Nitecore IFD2 - 260 Lumens x .67 hours = 174 lumenhours.

Click to expand...

If lumenhours is your buying criterion then this one should cost 174/440 = ~40% of the 440 units.