3.4a draw with 25r battery… is this pretty good?
i feel more amps can be had with a FET DD driver… switch has braid and so does driver. what can I do to get this to draw 5+ amps?
Explain how you are measuring this, & with what equipment.
Is the battery @ full charge?
What FET?
Using thin multimeter leads??
FET is from RMM, Battery full charge topped off 4.2v
fluke leads tailcap removed “bypassed for amp reading”.
was really hoping for some serious amp draw here and either I got spoiled by my mtg2 and XHP builds that xml2 just don’t cut it for me anymore…… lol
The majority of standard leads won’t cut it. Try making some from short 18g wire.
16 awg..... is what I'm using now
How long are your 16ga leads? I use 8inch 12ga leads.
I would expect your led to be pulling a little over 4amps on a good, fully charged battery
3inch long.
the emitter and noctigon are from INTL’outdoor.
Really? I thought two previous comments were about the multimeter probes. You also wrote "Fluke leads" in reference to the multimeter. Are you really using 75 mm wires, why, and does Fluke really make such(or have you cut them)?
I I wanted to minimize current measuring leads' resistance, I would use even heavier wire and still make them 300 mm or something to make them easier to use.
Also, what current/multimeter are you using?
Oops the leads on the meter are your standard length… probably 12”.
the leads on the driver are 3”.
i don’t see a reason to use shorter leads on a $300 tool
You should, Ohm's law remains Ohm's law, no matter how expensive the tool is, there are some $3000 bench multimeters athat are the worst thing to use when measuring current in series with the circuit. (BTW I own expensive tools too)
If you have another multimeter, try measuring the voltage drop in the Fluke leads. That should give you an idea of how much voltage is being burned by the long leads. 
It’s not about meter accuracy or quality. Essentially, you could be operating the meter out of spec for this particular purpose. This is also a case of measurement affecting the event to be measured.
There is no reason to use(or benefit to be gained from) shorter or thicker leads even on an expensive high end instrument if we were measuring just mean DC voltage(high impedance through meter). It is good to minimize resistance when measuring current (the meter and probes are part of the actual main circuit). It also depends on case and in this particular case it's even more important.
When measuring flashlight tailcap current, we have a losing battle against the very properties of the other components. The theoretical efficiency loss of 1% would not matter at all, but it's not about that. A tiny resistance is altering the whole circuit's operation. With a linear regulated driver this just might be important and with direct drive of high output FET drive it is critical.
Under other circumstances this would all be different and the test leads might not matter at all. Even when doing a tailcap reading with a boost driver. Probably even when measuring a linear regulated XML2 driven at 2A. It's not twice as important at 4A, it's 100 or 1000 times more important.
This has to do with the very basics of such a circuits design. A single cell single emitter high power LED system is functioning barely in those limits. What even makes DD possible and practical is the fact that the LED forward voltage increases when current increases and the li-ion cell's voltage decreases when the circuit current increases, and those meet creating a stable homeostasis before reaching critical current that would destroy the LED.
Exactly. When this data is combined with the LED datasheet, it should become obvious why this is important. 1 or 10 millivolts make a difference here. Even 100 millivolts might seem like a little as it's just like 3-4 percent of the total circuit voltage, but it's a huge amount. It would be fairly small if this was a scenario of linear resistance. But this is about driving a high current semiconductor that's very voltage sensitive, and doing so from an unstable power source that has significant internal resistance. Direct driving (or pseudo-direct driving) LEDs is very non-linear.
If you were to direct drive a heating element, this would not be that important. Or if you were using a current adjustable boost driver to drive a 6 volt LED from a single li-ion cell, or a 3 volt LED from a NiMH cell.
Ryansoh3
Check specs on Keithley 2000, the voltage drop in the multimeter is at 3A it is up to 1V, voltage drop in leads don't even matter at that point. In newer models I have seen it specified even higher.
That is my point regarding the cost of a tool, and the Keithley 2000 costs $1140
Keithley of course it is a reputable brand in high end circles and you probably would not buy it for high amp in series readings but for huge voltage resolution display and accuracy.
http://www.farnell.com/datasheets/1484284.pdf
Tried thee meter on another xml2 build that uses a 3.04a driver, guess what ? I’m seeing 3.04a so
No matter what the results are, you still have to make the effort to understand Ohm's Law cannot be avoided by buying an expensive DMM. The major thing in flashlight DIY-ins to understand that fundamental law, again no matter of what are the results you can't ignore it if you want to check circuits.
Despite everyone’s efforts to help you understand, we can only lead a horse to water….
How can you lead a horse to water when a pencil cant be lead?
I think they took the lead out, ’cause the kids were getting sick from sucking on them… 
of course it can’t be avoided.
why after several builds would one circuit need measurements in a different form?
I will remove a lead off the MCPCB and read the amps with 3” leads on the DMM. Does that make for a proper measurement?
The issue is resistance/Vf. The same reason we haven’t been able to hit 6amps off a single cell with the new emitters. As current increases, the long leads add Vf to the circuit to the point where the battery can’t push any harder. So your long leads could be just fine under lower amp draws but not work well for higher amps. Also, they could work fine with 6v builds (even high amps) because the batteries have so much extra voltage in series, but not work great on a single cell. There are lots of things to consider.
And there’s no guarantee your leads are the problem, but it’s usually the first place i suspect