(s)MJLED and lithium primaries

[Buck91]

Well I've read that the MJLED is rated for 2.8-3.2V. I've also read that many people have had issues with driving off a pair of lithium AA's as this can result in >3.2V as they have been known to measure as high as 1.8V per cell.

I guess I'm trying to find out if these facts are accurate or not as I have a MJLED (maybe SMJLED, bought it when I was getting into lights which happened to be during that transition period) AA minimag which rarely gets used, but I would definately like to have this at-the-ready for a power outage or anything worse. As of now it has alkalines in it, which I don't completely trust for a few reasons.

If I stuck some e2 lithiums in there rated for around use-by 2015, I would think I should be alright. I guess if I measure them and they are around 1.5-1.6V each I should be alright no matter what?

 

[Hondo]

This was the reason that it was recommended that you "break-in" the lithiums for 5-10 minutes in another device before using them to direct drive an MJLED or SMJLED. They are only at their very peak for a short time from brand new. Tests have shown that at 105 mA, the LED will degrade rapidly, but at 75 mA, it is quite durable with respect to long term lumen maintenance. I have found that with lightly used E2's, I am only getting around 50 mA draw from the cells, which should be very safe. I don't think I have ever had the best example of "new" lithium AA's to try, as all of mine came from a bulk discount in which some cells were of questionable capacity. Mine are all marked 2019, and mostly measure open circuit voltages of 1.75 - 1.85 volts, so my only concern with yours at 1.6 volts would be that they are not going to give you the 30+ hours of service to 50% that near-new cells will.

Also, the drive currents will vary from LED to LED, as the forward voltage varies. So it would be a good idea to put an amp meter across the tail before you close it up to make sure you are not over 75 mA, then you can be sure it will have a long and happy life.

Hondo

 

[Buck91]

Weird... they were rading 1.79v (the e2's) before i put them in for amp check. Now they are down to 1.62v; let me explain.

Checked voltage on aklies -1.52v each
Draw on alkies - 154mA!! Up from starting of 75'ish
e2 voltage 1.76v and 1.68v
draw 160mA

So considering the closeness of these numbers I left the e2's in and fired it up and just kinda let it run for maybe 3 minutes or so. Played around with the terralux t/c switch and the stock twisty. Pulled them out and rechedked voltage; 1.65 and 1.67... OK it appears they like to rest or something, I dont know. Draw is now up to 184mA on e2's.

So my quesion would why am I getting such a high current draw on aklies as well as e2's? Is it just because the alkies are fresh? I want to leave the e2's in there, especially with the close proximity of the current draw, but I need this light to work when needed, so I don't want to risk it if I may be overdriving the led.