On Wednesday, February 22, 2017 at 8:48:12 PM UTC-5, micky wrote:
I have one of thoe little 2.5" LED flashlights, that have 9 small LEDs
and use 3 AAA batteries. It's like the ones that Harbor Freight
sometimes gives away free, same size, but nicer.

The guy I bought the first one from said it would run for days on one
set of batteries, but I forgot that it was still on and i put it in my
pocket and an hour or two later, I noticed it was on because it was
warm.

It's still really bright, but if it's noticeably warm, how long can the
baterries really last? Certainly not two days. ?


I once, recently, forgot the screen was lit on my 5.5" smart phone and
only noticed because it felt warm in my pocket.

It's got a proximity sensor but I don't remember what it's supposed to
do.

The heat is from the LEDs, not the batteries, and no, the batteries will not last indefinitely. I would guess (SWAG) that each LED will run about 50 ma. So you are pulling 450 ma, or thereabout per hour. If your AAA batteries are middle-of-the-road 1,000 MAH, you have a base of 3000 MAH, so, about 6-7 hours +/- or so. Under normal use, that is 'days'.

Peter Wieck
Melrose Park, PA