Leaving you Light on

[FlashlightKid]

I was thinking that I would keep one of my Extreme III's set on P1 at the lowest setting. I believe this is 2% output, but i'm not sure on the lumen output at this setting (its super low, i'm guessing about one lumen). With it on this setting I was planning on keeping it on as a beacon/glow so I can find it easily and then switch it to P2 for more light. If it matters its also running a rebel emitter, not the newer SCC or Cree.

:candle:My question in whether this will have any negative effects on the LED's life and flashlight circutry.

:shrug:My thinking was that the current was so low that the LED would not be effected and the circitry should not be effected since the only ware item there is the EEPROM which would actually be written to less due to it not being turned off, thus saving the setting and performing one read write cycle.

I am not to concerned with recharging the batteries more often and if anyones interested I plan on posting my estimated runtimes (on lowest setting constant) if this ends up working out.

Thanks for your help, and hope to hear your responces.:thumbsup:

 

[45/70]

The only thing I can think of that might not be so good, is when you discharge at that low a rate, you can over discharge a NiMH or Li-Ion cell.

As I remember the shutdown voltage on the Extreme III is 0.8 Volts for NiMH and 2.8 Volts for a 10440. Keep in mind that at low discharge rates, the cells will actually be discharged to this level, as opposed to their voltage recovering as it does when the light shuts down at a medium or high rate of discharge. I just wouldn't run the light on the low setting when you suspect the cell capacity is at the low end.

Other than that, you should be fine. The LED and circuitry would probably last forever at that level. Heat sure isn't going to be a problem!

Dave

 

[McAllan]

0.8 volts shouldn't be a problem for NiMH. Although some chargers could refuse to charge it though.
Either use another charger or give it 10 min in a dumb charger. Don't leave it discharged for long though or the battery will be very lazy needing either a special break in program or simply a few cycles to gain it's capacity.
What isn't good for NiMH is cell reversal but since there's only one cell (did a google search for the light, hope I'm correct) that's a non issue.

I agree with the OP that memory modes of the kind that's saved to eeprom or the like is a twin edged sword. It's not very optimal constantly writing value to eeprom and if light is used regularly it has the potential of wearing out faster than you think. Eeprom and flash (not very different principle though different interfacing) has actually very limited write cycles. So I don't really like memory either and then there's the issue of knowing/remembering what the last used mode was. It's just easier turning it on and quickly cycle to the desired mode IMHO.

Unfortunately it seems more and more difficult to avoid such lights. If only they had a solder connection "jumper" in the head you could make or break when you've put it at desired start up mode and from then on don't do any writing to eeprom/flash. That would be a very usable compromise.

 

[FlashlightKid]

Thanks for the input.

Also for anyone interested I ran the light non-stop at the lowest setting for ~2days (maybe a couple hours off) on a duracell (old not new LSD) NIMH and it went from 1.4 volts to 1.2. I'm not sure if this can be extrapolated to mean that the light will last ~5 days before reaching .8v thus being dead.

I was planning on running it the full length of time, but decided I needed to use the other levels sooner (thus ending the test), and found it annoying to run it non-stop all day and night as a glow mode (i'll only use this mode when I need it).

Regardless the runtime is long on its lowest mode.

 

[45/70]

Thanks for the input.
Also for anyone interested I ran the light non-stop at the lowest setting for ~2days (maybe a couple hours off) on a duracell (old not new LSD) NIMH and it went from 1.4 volts to 1.2. I'm not sure if this can be extrapolated to mean that the light will last ~5 days before reaching .8v thus being dead.

Just as info, when a NiCd, or NiMH cell reaches 1.2 Volt OC (open circuit), they are pretty much dead. I doubt it would have taken more than 2-3 hours before the cell was at 0.8 Volt OC. Again, discharging NiMH cells to 0.8 Volts under such a low discharge rate, is not really good for them.

If you discharge a NiMH cell, and the voltage doesn't recover to ~1.20 Volts after a few minutes, you have over discharged the cell. The farther below 1.20 Volt the cell recovers to, the greater the possibility of damage to the separator. A recovery to less than 1.00 Volt, is a positive indication that some degree of permanent damage has occurred to the cell. NiCd cells are different. Their separator is much more robust, and they can be discharged to zero Volts on occasion, but it's very bad for NiMH cells.

Most of the time you read about discharging NiMH cells to 0.8 Volt, the load applied is great enough that the cell will recover to 1.20 Volt after a few minutes. When discharging at very low rates however, there is a point where this won't happen, and the cell will recover to an unsuitably low voltage.

Dave