The Malkoff Front Porch

Dicaeopolis

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Yes. It is reduced output. I was wondering if there is a difference in the reduced output. I think it is about 80 lumens. I have an older M31W, but was thinking about getting the cool version. I really wish Malkoff would make a single AA TAC version, but I don't think there are any plans for that. Maybe that would be a possible group buy thing if there is interest, I don't know.
 

kerneldrop

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Yes. Thank you. That is what I figured, but wasn't sure, since it really wasn't designed for a single AA.

How it works is that you need a certain voltage to turn on the LED...and in a way turn on the driver.
The driver is going to boost the voltage up.
the lower your voltage the higher your mah is required.
the higher your mah the less time your light shines.
the higher your voltage the more bright your led will be because the energy is more intense.

So a AA will work, just won't last as long and won't be as bright since Malkoff doesn't use constant current drivers.
 

LEDphile

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How it works is that you need a certain voltage to turn on the LED...and in a way turn on the driver.
The driver is going to boost the voltage up.
the lower your voltage the higher your mah is required.
the higher your mah the less time your light shines.
the higher your voltage the more bright your led will be because the energy is more intense.

So a AA will work, just won't last as long and won't be as bright since Malkoff doesn't use constant current drivers.
Hm, my measurements on an M31LL indicate that the driver appears to be constant current from the LED forward voltage down to whatever voltage results in a 1A input to the driver (about 1.2V in this case). So an M31L is probably a bit much for a single alkaline or NiMH AA to drive it into regulation, but you might get lucky with an L91.
 

kerneldrop

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Hm, my measurements on an M31LL indicate that the driver appears to be constant current from the LED forward voltage down to whatever voltage results in a 1A input to the driver (about 1.2V in this case). So an M31L is probably a bit much for a single alkaline or NiMH AA to drive it into regulation, but you might get lucky with an L91.

Does constant current mean that the LED has the same output until it shuts off? I might be confused. All of thermal’s test have every Malkoff’s output declining as the battery drains.

Maybe I’m mixing up constant current with being regulated?
 

LEDphile

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Does constant current mean that the LED has the same output until it shuts off? I might be confused. All of thermal’s test have every Malkoff’s output declining as the battery drains.

Maybe I’m mixing up constant current with being regulated?
Constant current is a type of regulation. With LEDs, it results in essentially constant output. The Malkoff M31LL I measured has three operating ranges:
  • Above the LED voltage, where the regulator switches to direct drive mode (and you can fry the LED via overvoltage if you aren't careful)
  • Regulated (LED is at a constant brightness regardless of input voltage)
  • Below the point where the input to the driver is approximately 1A for regulated output. In this region, the boost converter appears to fall back to a fixed ratio, and the output will vary with the input voltage.
The second 2 modes explain the constant output followed by declining output that is evident in the runtime tests of the various Malkoff drop-ins. And the transition point between regulated and unregulated being current-dependent explains why the lower output drop-ins do better at low voltages than the higher output units.

And before you try to calculate where the cutoff point is for a given M31 drop-in, note that the boost converter gets less efficient as the input voltage drops, and that LED forward voltage is also a factor, one that will vary with the specific LED.
 

kerneldrop

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@LEDphile -

Thank you for the explanation. I didn't realize the regulator can switch to direct drive mode.
So, on the M91 specifically...Malkoff website has this: "The input voltage is 5.5 - 12 volts. Below 5.5 volts it will drop out of regulation."
This can be just in general -- but why would the dropin be brighter using 12 volts, than it is using 9 volts if it's within regulation?
 

fulee9999

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why would the dropin be brighter using 12 volts, than it is using 9 volts if it's within regulation?
it shouldn't be... or at least none of my drop-ins have any visible difference in output while they are inside the regulated voltage
 

kerneldrop

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it shouldn't be... or at least none of my drop-ins have any visible difference in output while they are inside the regulated voltage
I guess I’m getting posts mixed up. I thought super hard Malkoff users find the M61 and M91 have higher outputs when multiple batteries are used?
 

fulee9999

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I guess I’m getting posts mixed up. I thought super hard Malkoff users find the M61 and M91 have higher outputs when multiple batteries are used?
I for one can't see any difference between the 2-3 CR123 and the one or two li-ion outputs, neither in the M61, M91 or the Hound Dog 18650 for that matter. If it drops out of regulation because of low voltage, now that you can see.
 

thermal guy

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There is definitely a difference when using higher voltage In some. for example you use a M61T on a single lithium as opposed to two or even two primary cells you will see a difference. A lot brighter on higher volts
 
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