I used a new Panasonic NCR18650BD button top and charged it again after every test. So each “run” started with the cell showing 4.21/4.22V (it must have been like 4.218 or something because my meter, 2 decimal point digits, flickered back and forth between 4.21 and 4.22)
One would think I used 2 of the same everything, they’re so close. I think the A17DD-S08 is doing a fabulous job, and in my triple and quad lights it’s definitely up to the task.
Thanks again Wight!
Edit: Notice the low high end amperage, and the resulting lumens output. The new XM-L2 U3 1A’s…
Dale,I think it's simpler to just measure parasitic resistance of each driver.And based on that number you can tell which driver will provide more current on high(if all other factors like battery,led Vf,springs wires are the same).
For DD drivers this is very easy:you need one ammeter and one relatively precise voltmeter,battery or power supply(better),led or resistor as load(not important,xm-l,xp-g...).
Connect driver,led and battery(or power supply) as usual(you don't need host),and ammeter in series for current measurement. At the same time measure voltage(mV range) across driver's "power" connections-GND and led cathode pad.
Parasitic resistance is then: R(par)=U/I
And that's it,repeat the same procedure for other driver(important thing is that it's best to use the same battery at same voltage and same load,because mosfet parasitic resistance Rds, which is dominant part of total parasitic resistance in DD drivers, depends on gate voltage).
You’re saying if I measure the off amperage at the negative end of the cell, and the Voltage between LED negative and ground, then divide which by which to get parasitic resistance?
Touching the LED negative to ground will normally give direct drive, right? So this is where I take a Voltage reading? While taking an amperage reading at the tail?
I’ll either pull the light engine and do this, or remove the bezel and use the host as a holder for the assembly of light engine/cell. I can use my older DMM with short 12ga copper leads to do the amperage reading, my clamp meter with probes hooked up gives very small Voltage readings.
Edit: Is the lower parasitic resistance driver the one that will make the highest power output?
First,as RMM said,you must measure current and voltage on highest(no PWM) mode.
Parasitic resistance for first driver is 6.22mOhm (miliOhm) which sounds about right,slightly higher than mosfet Rds;
but something is wrong for 2nd one, 21.34mOhm is too high for that mosfet? Value should be similar to first driver.
For fair comparison,it's important to measure parasitic resistance at same battery voltage,because mosfet's Rds usually starts to grow rapidly at voltages <4V(of course,that depends on mosfet)
My not so able bodied and not so willing partner in crime made it a big issue this morning. Geesh, just wanted a little help! lol
miliOhm huh, I was guessing on the Ohm connection studying Wikipedia on Ohm’s law. lol
I did both repeatedly, the Clamp meter is Auto sensing and gave me Voltage on the first one, then mV on the next and wouldn’t switch over. So I did them each repeatedly, arguing with the cranky wife, we both yelled at the kid, and ultimately I tested them again by myself holding the amperage leads on the cell with my tongue. Now it’s me that’s cranky! Vroooom! I started! Woohoo!
I’ll charge up the cell I used and try again. With peace and quiet the prevalent factor.
Nice job Dale! Sorry, very busy at work now - no time for BLF during working hours and long days. Was just about to try a Mattaus v1.0 driver in the X6 - not sure if it's worth it now, but using 20 AWG of same exact length each, it will still tell me how they do in the exact setup, same light, same LED, etc.
Not a thread - just finished some tests with the BLF17DD v1.0 using the de-domed XP-G2 S2 and got about 0.15A to 0.18A higher, depending on the cell (SAM 25R or LG HE2). Best #'s for each driver:
A17DD-S08: LG HE2 @4.23v: 3.78A @tail
BLF17DD: LG HE2 @4.22v: 3.96A @tail
Same host, same LED (didn't even remove the LED - it's screwed down), same 20 AWG wire lengths for LED wires, same 22 AWG wired driver spring setup (different spring but don't think that should matter), same batteries.
Conclusion:
Well, with just one sample of each, there can be variables I'm sure: quality of reflows, tight driver mount, battery charge differences, FET variations, etc.. Seems slight edge to the old BLF17DD which is kind of what I suspected, but since I only tried one A17DD-S08 up to this point, I can't say anything definite from this - too little data, not enough samples tested, don't 100% trust my methods, measurements, etc. It's not lab level for sure... I would trust djozz more than myself - absolutely .
Several other options are discussed in this thread. Did you look for those? Rufusbduck suggested one I really liked and I think there were a couple of others which sounded OK too.
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