Justin Case
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You might also check the new Malkoff MD60 tower.
Show your 12P/12ZM/12PM(T3,SRTH,or mod, NOT M4) !!
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You might also check the new Malkoff MD60 tower.
Size15's
Flashaholic
The 12ZM and 12PM were supplied with either the TRTH (Threaded Rim) or SRTH (Short Rim) TurboHeads. Both are 2.5" diameter.
The "KT" and Millennium TurboHeads are also 2.5" diameter.
SureFire's T-Series Extended Range TurboHead was 3" diameter.
All these accept either the N-type (N1/N2/N4/N5/N62) or MN-type (MN15/MN16/MN20/MN21/MN60/MN61) TurboHead Lamp Assemblies.
The 12ZM features a CombatLight body for four-SF123A batteries.
It is possible to build a four-SF123A body using a three-SF123A + A19 adapter but if you use a "9V CombatLight" body such as the 9Z or Z3 with an A19 you'll find it difficult to reach the CombatGrip unless you have monster hands.
Thanks for the heads-up. Every time I consider a Malkoff assembly they are out of stock (as they are with this assembly). The brass tower is appealing but the 6.5V to 14V driver seems targeted at 3S and 4S primary and 3S Li-Ion power sources. The Nailbender 3.4V-9V driver seems better suited to the 2S 18650 application I am equipped for.
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Justin Case
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I'm not sure I follow why the MD60's 6.5V lower limit means that the Nailbender tower is better suited to 2S 18650. By the time each 18650 cell is at 3.2V, it is essentially completely depleted. In fact, a 3.4V lower limit IMO means that you have a greater chance of overdischarging your cells.
Some of my salvaged computer pack 18650's have reasonable capacity but suffer from high levels of voltage sag under high drain. A pair of these cells can sag to 3.2V when providing 2.8A to a LED without necessarily being "essentially completely depleted". These same cells are, as you observe, essentially depleted when I capacity check them on my old MH C777PLUS charger that can only discharge test at 0.33 A.
Justin Case
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Well, your first claim was that the MD60 wasn't as suitable for 2S 18650 vs the Nailbender tower. Now you've clarified that your 18650s are not really suited to deliver slightly more than 1C.
So I still don't understand your claim that the nailbender product is the better choice. The Malkoff link for the MD60 says that the tower draws 0.8A at 9V. Thus at 7.4V, you might draw about 1A. At 6.5V, about 1.1A. So I'm not sure where you get your 2.8A current draw figure for the MD60.
If the nailbender tower has the same driver efficiency and drive current as the Malkoff tower, then they are going to have the same battery current draw. So I don't see any issue regarding current draw and battery sag.
The Malkoff MD60 is advertised to deliver 450 OTF lumens. If we assume 40% lumens loss, that means 750 emitter lumens. For a T6 bin XM-L, that suggests about 2.4A drive current. The datasheet says the Vf is about 3.25V. If the driver is 85% efficient, then
0.85*7.4V*Ibatt = 2.4A*3.25V = 7.8W
Solving for Ibatt gives about 1.2A at Vbatt=7.4A. That's a bit higher than the value estimated above based on Malkoff's figure of 0.8A draw at 9V. If the lumens bin is actually S2, then the drive current could be closer to 2A and Vf about 3.2V, giving
0.85*7.4V*Ibatt = 2.0A*3.2V = 6.4W
Now Ibatt calculastes to 1.0A.
However, the point is that any reasonable set of assumptions gives a battery current draw of around 1A. If your 18650s can't hold their voltage at that draw, then you need better quality cells.
So I still don't understand your claim that the nailbender product is the better choice. The Malkoff link for the MD60 says that the tower draws 0.8A at 9V. Thus at 7.4V, you might draw about 1A. At 6.5V, about 1.1A. So I'm not sure where you get your 2.8A current draw figure for the MD60.
If the nailbender tower has the same driver efficiency and drive current as the Malkoff tower, then they are going to have the same battery current draw. So I don't see any issue regarding current draw and battery sag.
The Malkoff MD60 is advertised to deliver 450 OTF lumens. If we assume 40% lumens loss, that means 750 emitter lumens. For a T6 bin XM-L, that suggests about 2.4A drive current. The datasheet says the Vf is about 3.25V. If the driver is 85% efficient, then
0.85*7.4V*Ibatt = 2.4A*3.25V = 7.8W
Solving for Ibatt gives about 1.2A at Vbatt=7.4A. That's a bit higher than the value estimated above based on Malkoff's figure of 0.8A draw at 9V. If the lumens bin is actually S2, then the drive current could be closer to 2A and Vf about 3.2V, giving
0.85*7.4V*Ibatt = 2.0A*3.2V = 6.4W
Now Ibatt calculastes to 1.0A.
However, the point is that any reasonable set of assumptions gives a battery current draw of around 1A. If your 18650s can't hold their voltage at that draw, then you need better quality cells.
JustinCase:
The 2.8A delivered to the LED is for the Nailbender. I did not calculate the current delivered to the Malkoff but agree with you that it is likely to be less than 2.8A.
I'm happy to accept your contention that the Malkoff will work fine with newer batteries. Note my other comment in post 57 that 3S weaker older 18650 batteries (read sag prone batteries) are used in a light with an MN61 and older SF turbohead to avoid significant overvolting to the MN61.
The linked thread asserts that the following differences in current draw occur with the MN60 and MN61 LA's when driven by 4S primaries and 3S Li-Ions, respectively.
"Surefire M4 "Devastator" 12V
MN 60 M4 LOLA -1.48A (1.65A on 3 Li-Ions) 20W
MN 61 M4 HOLA -2.51A (2.85A on 3 Li-Ions) 32W"
(MN60 current delta is 0.17A while MN61 current delta is 0.34A - twice as much using whatever reference 18650's were used.)
http://www.candlepowerforums.com/vb...urrent-draw-SF-amp-other-brands-incl-hotwires
When I use 3@ "tired 18650 cells" the brightness is equivalent on an MN61 to that provided by 4S primaries suggesting that the combination of voltage sag and current delivery capability approximates that of primary cells. The voltage sag on primaries when using the MN60 is enough lower than that with the MN61 that I can use full strength 18650's without prematurely burning out the LA.
Ergo, my assertion that my tired 18650's sag significantly while delivering something in the neighborhood of 2A to 2.5A.
The 2.8A delivered to the LED is for the Nailbender. I did not calculate the current delivered to the Malkoff but agree with you that it is likely to be less than 2.8A.
I'm happy to accept your contention that the Malkoff will work fine with newer batteries. Note my other comment in post 57 that 3S weaker older 18650 batteries (read sag prone batteries) are used in a light with an MN61 and older SF turbohead to avoid significant overvolting to the MN61.
The linked thread asserts that the following differences in current draw occur with the MN60 and MN61 LA's when driven by 4S primaries and 3S Li-Ions, respectively.
"Surefire M4 "Devastator" 12V
MN 60 M4 LOLA -1.48A (1.65A on 3 Li-Ions) 20W
MN 61 M4 HOLA -2.51A (2.85A on 3 Li-Ions) 32W"
(MN60 current delta is 0.17A while MN61 current delta is 0.34A - twice as much using whatever reference 18650's were used.)
http://www.candlepowerforums.com/vb...urrent-draw-SF-amp-other-brands-incl-hotwires
When I use 3@ "tired 18650 cells" the brightness is equivalent on an MN61 to that provided by 4S primaries suggesting that the combination of voltage sag and current delivery capability approximates that of primary cells. The voltage sag on primaries when using the MN60 is enough lower than that with the MN61 that I can use full strength 18650's without prematurely burning out the LA.
Ergo, my assertion that my tired 18650's sag significantly while delivering something in the neighborhood of 2A to 2.5A.
Justin Case
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Those numbers are all well and good, but they are irrelevant. You simply won't draw that much battery current with the MD60. It clearly uses a buck driver and the battery current draw will scale with Vbatt/Vf.
As I wrote before, if anything the nailbender tower is less suited to 2S 18650 than the Malkoff MD60. Because the MD60 lower voltage limit (presumably for full regulation) is 6.5V, when each cell reaches ~3.2V under load, the light will start to dim because it has fallen out of regulation. This is an indication to change our your cells and serves as an excellent visual indicator to protect your cells from overdischarge. At that Vbatt level, Ibatt might be an estimated 1.2A-1.4A. Pretty mild draw -- around 0.5C for your typical 18650 these days.
In contrast, at the nailbender tower's min voltage of 3.4V, you will basically run down your cells until they croak or the cell's protection circuit trips to protect against overdischarge. That is far less kind treatment to Li-ions.
Edit: I want to clarify that I personally don't find either tower specs to be a hindrance wrt using 2S 18650 and I would be comfortable owning and using both products. But you have to understand the impact of the specs operationally. A low driver voltage to stay in regulation is great if you want to have the flexibility to use 1xLi-ion as well as multiple Li-ions. The nailbender tower looks like it is very suitable for that, while the MD60 is not. However, when it comes to 2xLi-ion, the Malkoff is the more forgiving product IMO because of the reduced likelihood of overdischarging the cells. But that also depends on your usage pattern. If you use your light for some known amount of time per day, for example, then it should be relatively easy to keep track of run time and re-charge the cells periodically to avoid overdischarge. But if you are not so diligent or it is not so convenient to track run time, then you have to assess whether this is an important issue or not and factor that into your selection criteria.
As I wrote before, if anything the nailbender tower is less suited to 2S 18650 than the Malkoff MD60. Because the MD60 lower voltage limit (presumably for full regulation) is 6.5V, when each cell reaches ~3.2V under load, the light will start to dim because it has fallen out of regulation. This is an indication to change our your cells and serves as an excellent visual indicator to protect your cells from overdischarge. At that Vbatt level, Ibatt might be an estimated 1.2A-1.4A. Pretty mild draw -- around 0.5C for your typical 18650 these days.
In contrast, at the nailbender tower's min voltage of 3.4V, you will basically run down your cells until they croak or the cell's protection circuit trips to protect against overdischarge. That is far less kind treatment to Li-ions.
Edit: I want to clarify that I personally don't find either tower specs to be a hindrance wrt using 2S 18650 and I would be comfortable owning and using both products. But you have to understand the impact of the specs operationally. A low driver voltage to stay in regulation is great if you want to have the flexibility to use 1xLi-ion as well as multiple Li-ions. The nailbender tower looks like it is very suitable for that, while the MD60 is not. However, when it comes to 2xLi-ion, the Malkoff is the more forgiving product IMO because of the reduced likelihood of overdischarging the cells. But that also depends on your usage pattern. If you use your light for some known amount of time per day, for example, then it should be relatively easy to keep track of run time and re-charge the cells periodically to avoid overdischarge. But if you are not so diligent or it is not so convenient to track run time, then you have to assess whether this is an important issue or not and factor that into your selection criteria.
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