Help / advice needed

[Didje]

I found that brand on eBay and I'm wondering if there's something wrong here.
900 lumens? EDI-T D4(900)-R-2×18650 LED Diving Flashlight

 

[wquiles]

Hey guys,

I did a night dive yesterday and quickly came to the conclusion that my 90 lumens light clearly wasn't powerful enough.
My buddy was diving with a UK C4 eLED and I was very impressed by its output. After doing some research on the interwebs, I'm getting quite confused
I see a lot of smaller lights that output more lumens than the quite larger C4 (for example). How can, say, 3 x AAA batteries output more than 4 x AA's?
I guess I have a hard time understanding how that can be, simply because I take for granted that the bigger ones will be more powerful. Is there something else, aside from the lumens, to be taken into consideration?
I apologize if this has been discussed before but I couldn't find anything on SB.
Thanks a bunch!

You have gotten very good advice so far. Truth is that when you go to LED-based lights for the first time, it feels like trying to drink from a fire hose - too much information.

Although not specifically written for diving lights, several months ago I wrote a post in the flashlight forum that provides a good high level view at flashlights, with a higher emphasis on LED lights. It might be good to read/review to get a better background on LED lights in general:
Introduction to modifying flashlights ...

I hope this helps

Will