Possible LED flashlight overheating?

One of my favorite flashlights has been acting up on me lately. This is mostly a pretty common light, you can find them at wal-mart all the time. made by black and decker, orange, and run about 20 bucks (19.88 i think) takes the 4 AA batteries, spotlight shaped, etc

The bulb in it, is just like the bulb in the mini mag LED and the 2D LED mag (i think it's called cree?)

I was using it last night and after being on for about 25 minutes, it just shut off, like the battery was dead. so i popped the batteries out and checked em with a battery tester and all the batteries were good. ( i had just charged them up the night before). so to be on the safe side, i checked them with ANOTHER battery tester and again they were good. so i put them back, turned it on and it ran for about 2 minutes then shut off again. so i just left it sit, and after about half an hour of sitting, i turned it back on and it ran good this time for again, about 25 minutes, then shut off. then time, when it shut off, i immediately switched it to low and it ran perfect on low. but as as soon as i'd flip it back onto high, it would shut off instantly. so i charged the batteries, and re did it. and lo and behold, it did the same thing as described above so i ruled out the batteries. so, as another test, i inserted some brand new alkalines in, and again the same thing happened.

mine only thought is, it could be over heating and shutting of maybe? i've had this light about 2-3 years, and it's probably my 2nd most used light (my most used light is another flashlight that looks just like this one, same brand and everything, but it takes 4 C batteries and i've had no trouble from it)

What is your take on this matter?

If it is overheating you should have noticed this behaviour before unless something recently broke in the light.

Are your rechargeable cells healthy and good quality?
If they are getting old or not very good from the beginning they can't deliver the needed current under load for prolonged time.
That could explain why it works in low mode but only for a while in high mode.

And alkalines usually aren't very good in high drain.

So, my suggestion is to get a set of new, high quality NiMh and try again.

GunnarGG said:

So, my suggestion is to get a set of new, high quality NiMh and try again.

Click to expand...

i'll put in my new set of eneloops i bought about a month ago and re try this and post what happens.

i used to use alkalines in this light back before i started using rechargeables, and back when i used alkalines, they wouldn't die this fast. they would at least go a few hours, but not die this fast. so i'll try it with the eneloops.

oh and to answer your question, the batteries i first used were a set of japanese made 2300 LSD energizer batteries i bought about 2 months ago.

i checked the specs on the light, it says it's a 3 WATT LED bulb is what's in the light

Just tried it with fully charged eneloops, they lasted 29 minutes before cutting off

please take a picture from the front, so we can say what led it is ...

then:
calculating with a typical 1.600 mAh (?) from good eneloops (at this draw) ...
(an I hope I get it correct now ...)
1600 *4 /3 /29 *60 = 4.413 mA per hour

... 4.5 A is a bit much, even if it were an XM-L

possibility:
the light is direct drive and/but with alkalines the draw is much less - these cells can not give this current ...

but my first guess still were the chemistry, the charger to name it.
Usually one tends to use "good" cells, but the chargers often are questionable.
A good charger - costs some bucks - gives better results
(good charger w. "cheap" cells = better than "good" cells w. cheap charger ... good charger w. "good" cells = best)
Does Your model charges the cells in pairs, or each cell individually?