SureFire E2DL low battery mode change ???

I have one of the earlier SF E2DL versions (the 200 lumen rated type, IIRC) and just noticed an odd "feature" ....

The UI on these is fairly simple - always starts on High, and cycle briefly for Low.

Recently went to use this for the first time in quite a while and the start mode (High) had been replaced with a fast Strobe.

It would still cycle normally to Low, and then back to Strobe. Regular (non-flashing) High was no longer available.

I switched to a different flashlight until I could investigate further. I then replaced the batteries with fresh and full cells and, not surprisingly, it returned to normal functioning.

When I tested the old cells on a ZTS, both read as below 10% capacity, essentially empty.

Is this strobe a "low battery warning" ... a known feature ?

I don't recall either this having been discussed before, or even ever noticing this happen, although I rarely run multi-primary battery setups all the way empty.

Anyone else notice this, or have related info ?

I don't believe mine does this, I have some dead cells I'll try out...

Although I would suppose you are aware of the risk(s) involved with running nearly empty primaries, a general warning for others who may happen to browse this thread is likely warranted. Accidentally forcing reversed polarity is possible in this situation, which can be dangerous.

My E1DL did just that on the first cell i depleted.

When dropped out of reg, it would turn on at maybe 50 lumens and slowly dim to almost the same brightness as low mode 5 lumens.

Repeating the process yielded the same results, until finally the high mode(maybe 30 lumens by that time) was replaced by strobe. I could still shift to low, like your E2DL.
Playing with it more, it finally refused to light up. Voltage was 1.98V and I removed the cell.

This is obviously not an intended feature, probably just the battery recovering just enough to put out a pulse of light, then deplete itself again, the electronics doing it fast enough to be strobe like.

I just found this review of the E2DL Ultra ...

http://flashlightguide.com/2013/05/review-surefire-e2dl-ultra/

... and it mentions the output "flashing" at the end of the runtime test.

I think this may be an undocumented feature.

I think that the strobing appears to be too fast and too regular to be a simple battery voltage drain / recovery pattern, at least on mine.

I've never seen my E2DL LED Defender do it, and I've had it for quite a few years.

Yes. Seen it a lot with mine. I use RCRs and when low the lights flash.

Sounds like it's a known occurrence ... thanks for confirming.

It is possible that SF may have used different drivers over time, as these changes are not always identified and promoted as such.

Mine does the exact same thing when not used for awhile. I just remove the tail cap, put it back on, and then it works normally. Kind of strange.