Runtime difference: Short bursts vs. long constant-on?

[etc]

I tested the Malkoff M60 setup with AW's protected 2x18500 cells.

I got 2:17 hours runtime which is what was expected.

Now I usually don't discharge the cells in one long shot but rather use it in short bursts, 30 seconds here, 2 mins there... and it just seems like in the latter case with "short bursts" I don't get the 2:17 hours runtime but a lot less.

Is there a rational explanation of this or is it impossible?

 

[D-Dog]

Other feel free to chime in and correct me if I am wrong, however, excluding battery self-discharge I would expect the same runtime. Your light isn't an HID where the larger startup current would affect runtime so I would have to guess they really are the same... or you have bad cells .

 

[Burgess]

This is a good question.



_

 

[Size15's]

I seem to recall that several members have experimented and been able to demonstrate that short-bursts of usage result in less output over the course of the runtime, and shorter overall runtime.
If I recall correctly this is due to the battery temperature cooling down between uses and energy being wasted heating the batteries back up to more efficient operating temperature...
Standing by to be corrected though. :candle:

 

[etc]

Would it be interesting if this delta could be quanitifed.

I cannot possibly seat there for hours, hitting the switch on and off every few mins for 30 seconds at a time.

It just *seems* there is a huge gap between burst-usage of Malkoff M60 vs constant cut-on for a couple of hours. It just "feels" like I am getting only maybe 1 to 1.5 hours with it.

I wonder if it's something inherent to Li-Ion cells.

Of course my perception could be wholly wrong.

 

[D-Dog]

Hmmm... I just don't know. LED's consume the same amount of current whether they run for a minute or 60 (If they are properly heatsinked... otherwise they would consume less current as the diode heats up (could lead to longer continuous runtimes)). Unless the batteries increase in temperature a noticeable amount, I don't think the internal resistance will be an issue as Li-ions already have decently low resistance, especially with only a 2 cell light. Quite an interesting question.

 

[divine]

I'm sure the circuitry in the light would affect this. Using the battery to charge capacitors, start inductors...

It used to be inrush current with incandescent lights, but I don't think there is inrush with LED's.

I don't have any numbers for this.

 

[signal 13]

I'm just excited to read that you can run the M60 on 2x18500s!

I see a Leef Body HA 9P in my near future!

 

[Sgt. LED]

Yeah the voltage is all the same. You can run any of these:
2 Rcr123
2 17500's
2 17650's
2 18500's
2 18650's

You just gain runtime with the slight drawback of a longer light. Of course that is a big issue with some and no issue with others, I think it depends on if you remember carrying a 4D Mag on your hip all day or not!

 

[Monocrom]

Best way to know for sure is to PM Gene, and ask him. (Gene43).

 

[Rudi]

Way back I tested several 123-lights comparing continuous runtime with intermittent (3 to 5 minutes) running, with at least a half hour until the next burst. Results were near identical, in one instance being off by one minute in 2.5 hours, and never by much more.

 

[etc]

Rudi,

Thanks for the feedback.
Still have a different module involved and a different cell chemistry.

I also ran this combo on 3x123, one reason why it's sweet, you can always go back to primaries. And in short bursts, I got a pretty reasonable runtime, better than 2x18500 cell runtime.


Indeed, 2x18500 & Malkoff M60 is a sweet combination.

 

[GPB]

I know with some lights, there is a overheat protection feature built in that reduces the current to the LED when it gets too hot. Take a look at a runtime graph of a MagLED and see the steep drop off in the first few minutes. By running it in short bursts you are getting the full brightness of the LED, which uses up your battery juice faster. By running it for a while, the heat protection will reduce the power, prolonging the battery drain. I believe that is the case with Mags, and I don't mean to insult a Malkoff by assuming it is in any way "mag-like" but I thought the info was relevant.

 

[etc]

I know the M60 is rated at well under 1,000 mAh of drain (Was it 800mAh?) but I wonder what the drain is in that short-burst mode?

 

[offroadcmpr]

I think it also depends on what battery chemistry is used. I seem to remember how some one tried it with a alkaline and got a longer runtime, and some one tried it with a lithium and got a shorter runtime. As the cells heat up as they are used continuously I think it may play with the runtime.

 

[LukeA]

I know the M60 is rated at well under 1,000 mAh of drain (Was it 800mAh?) but I wonder what the drain is in that short-burst mode?

The same. It's the battery chemistry that changes short-burst runtime.

 

[etc]

I wonder if 123 primaries favor the short-burst mode of operation more than Li-Ion 18500s or 18650s.

It seems that 2:17 hours runtime of M60 on 2x18500 AW's protected cells is theoretical and realized only when run non-stop. In actual use, the figure does seem lower.

With M60, bring your spares... I usually have 4x18500 spare cells.