Malkoff M61 2x18650 numbers??

mpkav · Apr 20, 2010

I've been searching around but haven't found any specifics on the M61 running on 2 18650s. What would the runtime be? Would there be any gain or loss of brightness over 1 18650 or 2 cr123s? This will be for duty use, am I better off going with 1 18650? Thanks for any help!!! :wave:

bullettproof · Apr 20, 2010

There will not be any difference.The only difference will be run time.The light stays in regulation down to 3.4 v if I remember correctly.I use a AW17670 in a C2 and Im getting right around 2 hours of runtime.

FroggyTaco · Apr 20, 2010

Seeing how "low" the current draw is for the M61 & the capacity of a 18650, I would stick to a single 18650 set-up & keep an extra battery on hand for when the first gets tired if ever on a single shift.

Travis

mpkav said:
I've been searching around but haven't found any specifics on the M61 running on 2 18650s. What would the runtime be? Would there be any gain or loss of brightness over 1 18650 or 2 cr123s? This will be for duty use, am I better off going with 1 18650? Thanks for any help!!! :wave:

mpkav · Apr 20, 2010

As much as I think about my lights I haven't considered a 1x8650 body and having a spare with me, kinda weird. I was solely thinking of the 2x or 1x and thats it. When I got my M61 I bought 2 AW's in anticipation of buying the 2x18650. Maybe I should go with the 1x and keep the light a little more compact!!! Thanks Travis!!

psychbeat · Apr 20, 2010

I like carrying a spare AW 18650 rather than having
a large light:thumbsup:

I almost NEVER need the spare but its nice knowing
its there. I just keep it wrapped in a sandwich bag
and its super light.

dont have any Malkoff modules- YET.

mpkav · Apr 20, 2010

Anyone have a rough estimate how long an M61 will run on 2 18650's? Or an exact estimate will work also!!!:twothumbs

txgp17 · Apr 20, 2010

mpkav said:
Anyone have a rough estimate how long an M61 will run on 2 18650's? Or an exact estimate will work also!!!:twothumbs

Two 2200mAh 18650's have about 1.9 times the amount of energy as two CR123's.

Gene says about 2 hours on a set of primaries. So you're looking at about 3.75 hours.

etc · Apr 21, 2010

I like 2x18650 format, it can also take 4x123 if the module can take up to 12V (Malkoffs generally cannot)

and the good thing about 3 or 4 123 cells is that they improve efficiency, not just the runtime.

Example, a 9P with Malkoff gets disproportionately longer runtime than 6P. I am sure a 4x123 lite does even better.

In a 4x123 configuration you can run either 18650s or 123s.

psychbeat · Apr 21, 2010

weird- how would more cells be more efficient?
dosent it mean the driver has to buck a buncha
voltage?

mpkav · Apr 21, 2010

etc said:
I like 2x18650 format, it can also take 4x123 if the module can take up to 12V (Malkoffs generally cannot)

and the good thing about 3 or 4 123 cells is that they improve efficiency, not just the runtime.

Example, a 9P with Malkoff gets disproportionately longer runtime than 6P. I am sure a 4x123 lite does even better.

In a 4x123 configuration you can run either 18650s or 123s.

ECT, is that an OD green body? Who makes it?

Liteskr42 · Apr 21, 2010

When I run my M61 on one 1x18650 Solarforce brand I occassionally notice that within 1 second of activating the lite the ouput drops just a little bit. Since I can notice it I would say it is dropping 20-30 lumens? When the 1x18650 is hot off the charger I do not notice this happening. Its when the 18650 has "calmed down" a bit to 3.7v . When I use 2x18650 this does not happen. I get maybe 45-50 mins runtime on 1x81650 and output declines steadily by 50mins. I could run it longer but I dont like to hit protection circuits on my batts so I stop when I really notice a drop in output and swap it out. I also notice a difference in heat going from a full charge to the 45 min mark . The head is warm at startup and not warm at all at 45 mins. With 2x18650s? I dont know if 3.75hrs is accurate or not.

That body looks like a LEEF. Awesome bods no longer made

mpkav · Apr 21, 2010

Liteskr42 said:
When I run my M61 on one 1x18650 Solarforce brand I occassionally notice that within 1 second of activating the lite the ouput drops just a little bit. Since I can notice it I would say it is dropping 20-30 lumens? When the 1x18650 is hot off the charger I do not notice this happening. Its when the 18650 has "calmed down" a bit to 3.7v . When I use 2x18650 this does not happen. I get maybe 45-50 mins runtime on 1x81650 and output declines steadily by 50mins. I could run it longer but I dont like to hit protection circuits on my batts so I stop when I really notice a drop in output and swap it out. I also notice a difference in heat going from a full charge to the 45 min mark . The head is warm at startup and not warm at all at 45 mins. With 2x18650s? I dont know if 3.75hrs is accurate or not.

That body looks like a LEEF. Awesome bods no longer made

I know, i've been looking in the market place for a leef to pop up but they're rare!!! Since I can run the M61 off my Z2 maybe I'll just go ahead and get the 2x18650 and try it.

etc · Apr 21, 2010

psychbat said:
weird- how would more cells be more efficient?
dosent it mean the driver has to buck a buncha
voltage?

I don't know about M61. But with M60, a 9P runs more than 1.5 times longer than 6P with the same module. Think of it as getting free runtime on 3 cells versus 2.
I assume it's identical situation with M61.

A 2xAA lite is also more efficient than 1xAA lite and produces more than twice the runtime.

etc · Apr 21, 2010

That's right, it's a Leef body.

The FiveMega 4x123 body is essentially the same thing. Might be a slightly better fit for the Malkoff modules. I have to use a copper ring in the Leef for better contact.

Bullzeyebill · Apr 21, 2010

psychbeat said:
weird- how would more cells be more efficient?
dosent it mean the driver has to buck a buncha
voltage?

Not really more efficient, but does run longer in regulation, and yes the circuit bucks the added voltage. Circuit is usually more efficient when vin is closer to vf of LED, but the advantage of longer runtime out weights any effeciency losses caused by added voltage. An LED is more effecient when it is run at low current such as the advertised lumen ratings (flux) of the high output LEDS when run at 350 mA's to the LED.

Bill

psychbeat · Apr 21, 2010

ahh- Im going to have to look up the runtimes of
the M30s etc.

the M61 driver seems more geared for 2 or more cells.

(maybe off topic)

so are lower voltage single cell (~3-6v) drivers less
efficient overall?

thanks for the info!

I still like single cell w a backup batt personally

Bullzeyebill · Apr 21, 2010

Single cell CR123 lights utilizing a boost circuit to run a light in regulation will mostly be more efficient than most buck drivers, as the battery voltage is already close to the vf of an LED that has, say a vf of 3-4 volts. Driving the LED at high current, say 1 amp to the LED, can put a strain on a single CR123, compared to using a buck circuit with two or more CR123's. Again, a buck driver will allow the LED to run longer in regulation.

Bill

txgp17 · Jul 15, 2010

psychbeat said:
weird- how would more cells be more efficient?
dosent it mean the driver has to buck a buncha
voltage?

This is how I understand it.

Say you run a 2x123 set up until the M61 emits 80 lumens. I don't know what that voltage would be, but let's just say it's 4 volts.

Now, when 2 cells are putting out 4 volts, that means each cell is drained until it's at 2 volts, because they're in series.

For 3 cells to reach the same voltage, each cell would be drained to the point of being only 1.33 volt per cell, thus each cell in the 3x setup has been drained to a lower point than the 2x setup, yet they provide the same overall voltage.

Amp load also comes into play, and the voltage drop from 3 cells would be less than that of 2 cells.

etc said:
That's right, it's a Leef body.

The FiveMega 4x123 body is essentially the same thing. Might be a slightly better fit for the Malkoff modules. I have to use a copper ring in the Leef for better contact.

I use a roll of aluminum foil.
I have two 2x18650 bodies from Leef. One black HA and one natural HA.

The natural one always needs the aluminum foil for my M60 modules, the black one never does.

Casper507 · Jul 15, 2010

You get a little more light running 2 vs 1 especially after it drops out of regulation on one cell. With one cell you get a longer runtime with light falling off as it goes to direct drive. Of course when using 2 cells you go down to the protection circuit you will be left in the dark with little or no warning. Personally the only reason I can see for using 2 18650s is because my Strobe switch won't work in constant on mode with a single 18650 or 17670. For some reason it needs the added voltage to stay constant on. Look around here and you'll find this issue covered for the M60. The M61 will just be a little brighter I believe.

Bullzeyebill · Jul 16, 2010

It is not the batteries that are more efficient, it is the voltage that is closer to the forward voltage of the LED that makes the efficiency. For practical purposes efficiency is not really that important to us. We like, a lot of us, the increased runtime that we do get with a buck circuit when we run the two or more cells. True, in that the M61 will operate in regulation down to about 3.4 volts, there is a risk that that the protection circuits when using multiple Li-Ions will cut in, but we should be seeing some decrease in output, if we are observant, before that happens.

Casper 507, which tailcap switch are you using?

Bill

Malkoff M61 2x18650 numbers??

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