Driver efficiency on a MTE M 3-2 (Measured!)

Hi everybody,

I buyed a MTE M3-2 from DX and like it very much, because of its nice throw on "high" and its very long runtime on "mid" and "low".

Today I dismounted it completely, attached some arctic silver instead of the old thermal paste and measured the following values in order to calculate the driver circuit´s efficiency:



Now I wonder why the efficiency is that bad on a regulated circuit!
Has anybody measured on this or other flashlights so that we can compare?

Best regards,
Peter

Simple - it's not regulated circuits. It's DD with set of resistors that's why eficciency is so low.

phantom23 said:

Simple - it's not regulated circuits. It's DD with set of resistors that's why eficciency is so low.

Click to expand...

Negative. Its definitely regulated with constant voltage output. Thats what I measured. Hmm... maybe a sort of regulated resistor, without any step-down-circuit. What a crap! I like the flashlight. Is there a real good step-down-circuit that has the normal size (19mm diameter or so) and can stand the high output of 6,5 Watts???
I would like to buy and replace

Ups - am I in the wrong forum with this topic? :thinking:

Ok maybe I asked too much, hoping to start an intelligent technical discussion. In this forum there is merely "blabla my great new flashlight blabla".

Sorry folks! And have fun anyhow :wave:

You might want to try the "Flashlight Electronics - Batteries Included" section of the forum. You can ask a moderater to move your post for you.

Hi all,
Just want to add that MrGman has the lumen readings tested and posted in his sticky. When used with a non-IMR cell the lumen readings were nearly 50% less. Then I suggested we top off an IMR 18650 and then the numbers are as follows:

MTE SSC P7___________,__1-IMR 18650,_____________________478.5__,___3 sec_______,
MTE SSC P7___________,__1-IMR 18650,_____________________416.8__,__30 sec_______,
MTE SSC P7___________,__1-IMR 18650,_____________________471.0__,__60 sec_______,
MTE SSC P7___________,__1-IMR 18650,_____________________467.3__,_120 sec_______,
MTE SSC P7___________,__1-IMR 18650,_____________________422.4__,_180 sec_______,
MTE SSC P7___________,__1-IMR 18650,_____________________390.7__,_240 sec_______,

The light is a direct drive P7 and has good spill with some throw. It actually looks much brighter than it really is due to the bigger reflector. It is a good buy, but if there was a way to regulate the current to 2.5A, but then the price would likely be higher.:scowl:

pm_wob said:

Hi everybody,

...
Now I wonder why the efficiency is that bad on a regulated circuit!
Has anybody measured on this or other flashlights so that we can compare?

Best regards,
Peter

Click to expand...

Why do you think a regulator must be efficient?

A linear regulator is conceptually just a big resistor circuit which monitors its output so the voltage or current is constant. It basically wastes (dissipates as heat) any power which isn't required by the output.

The cheap AMC7135 regulator circuits which seem to be popular for mods will waste a huge amount of power for this reason because it's a linear regulator. Basically, with 2 lithium cells driving a single LED with an AMC7135 board, the board efficiency is about 55% (wasting about 45% of the power).

The better LED drivers use a switching regulator, which is much more efficient (usually about 85% or better).

Toshi

TMorita said:

The better LED drivers use a switching regulator, which is much more efficient (usually about 85% or better).

Toshi

Click to expand...

Thats why I will pay more for a well designed light with a good circuit. This makes a light cost more and is not always apparant to a potential buyer.

I had a couple of lights in the past that consumed way too much power for the amount of light that they were putting out. They would compare favorably to other lights if the comparison was made only by looking at brightness. Runtime was poor on these due to the inferior driver circuit.

TMorita said:

The cheap AMC7135 regulator circuits which seem to be popular for mods will waste a huge amount of power for this reason because it's a linear regulator. Basically, with 2 lithium cells driving a single LED with an AMC7135 board, the board efficiency is about 55% (wasting about 45% of the power).

Click to expand...

AMC can't handle over 6V. Besides when you run low Vf emitter with single Li-Ion efficiency rises up to over 90%. That's why cheap AMC based circuits are still popular.

It's simple: more expensive flashlight, more advanced circuit.

phantom23 said:

AMC can't handle over 6V. Besides when you run low Vf emitter with single Li-Ion efficiency rises up to over 90%. That's why cheap AMC based circuits are still popular.
...

Click to expand...

That 90% figure sounds a little optimistic for an AMC7135 circuit on a single Li-on.

If you assume an low Vf emitter with a Vf of 3.2 volts and a Li-on cell about halfway discharged at 3.7 volts, then it's 3.2/3.7 = 86% efficiency.

When the battery is fully charged, it'll be more like 3.2/4.2 = 76% efficiency.

Toshi

pm_wob said:

...
Is there a real good step-down-circuit that has the normal size (19mm diameter or so) and can stand the high output of 6,5 Watts???
I would like to buy and replace

Click to expand...

The Sandwich Shoppe regulators have pretty decent efficiency.
Some of them can be run in parallel - try asking the electronics subforum.

Toshi