guts of an Eternalight X-Ray

Well it seems I just had to take apart the X-Ray to see what's inside, here's the scoop -

3 AA batteries, comes supplied w/ Energizer alkaline.

LOTS of empty space. There is a reason though, with lithium batteries the light floats, sinks with alkalines.

Circuit board (removed it). One 18 pin DIP chip, numbers sanded off! (I have heard of manufacturers doing this, just never seen it myself). Some SMT components, 4 white LED's and 1 blue LED that lights up in always on mode, and 3 microswitches.

Hooked it up to a regulated power supply, the circuit is stable at even at 2.3 volts, where the LED's are barely glowing at high setting. At 4.5v it draws 150mA, and is quite bright. As you adjust the voltage, the brightness varies across this range.

I'm going to put it back together, I like this light overall. I think you can make a case for buying lithiums, they keep a constant voltage (brightness in this case), make it float, and work under adverse temperatures.

I would be really curious to know if it maintains the 4.5v on hi until the batteries die or is it linear (follow the battery voltage)? Does it have the same output of 4.5 with alakline vs lithium? It looks to me like the lithium is a bit brighter, but I can't say for sure.

The output brightness follows the battery voltage, at the 'high' setting at least (only setting I tested). So alkalines would dim as they are used, lithiums should remain relatively constant.

Of course I tested with a power supply, not batteries, but with max load of 150mA either type of battery should be able to handle it without the output voltage dropping significantly.

You have a great flashlight site Brock, I saw how you rated the brighness of lights (mostly brighter = more bulb wattage). Very handy, also great comparison photos. So I had to buy the top of the chart M6. Should be here tomorrow, can't wait!