[sold out] SKY RAY 6 x Cree XM-L2 T6 3-Mode Cool White Light Flashlight - Black (4 x 18650) US$ 25,76 free shipping @ DX

Could always try stripping the solder mask over the traces and run a bead of solder to thicken the traces, then kapton tape the snot out of the top of the star

Are they the typical hi>lo hidden strobe? How bad was the PWM on the lower modes?

Wow…very nice SRK, definitely needs good heatsinking, is the star bonded to the pill or just silicon grease?

I wish my SRK had a pill, all I have is a star that sits on the shelf that was machined out where the threads “should” be…
(once I get the driver up and running right, I might go ahead and do the fill of epoxy behind it to see if that helps…yeah makes it permanent…but this is my first “test” SRK, definitely won’t be my last)

That is a scary thought, yes probably to much current and the trace did an imitation of a fuse. We have to be careful of that.

Too late to get stock readings on this light, good thing I have another coming from DX China. If it is the same exact light I will get the readings. I want to know too!

Spacing is pretty good. I can’t detect any PWM on low. I can hear it.
BTW, the older we get, the longer it takes for our eyes to adjust to changes in light levels. Maybe at my age I have “long persistence” eyes.

Maybe not scrape the whole trace, and not every one. Perhaps just the ones that are a bottle neck and perhaps just an area near the LED. I have some small gauge solid copper wire I can use (telephone wire). If need be that wire can be pounded flat first, insulation and all.
Or maybe connect to the little blob of solder coming out from each LED during the reflow process. That is risky though, may disturb the electrical and or the thermal connection.

Dchomak, first of all I want to thank you for taking the time to post your test findings. However, I disagree with your findings. That 6x XM-L2 MCPCB will pull FAR more than 10A on four good cells. In fact, I would be very surprised to see less than 20A on four good cells with heavy wire to the MCPCB. Mine pulled 13.2A from a single 18650, with the stock skinny wires, over 10A from a single IMR 18350. I am guessing that with 18AWG wire it will do 16A+ from a single 18650.

Something in your test setup is adding a lot of resistance.

If it pops may end up scraping off the solder mask then adding solder to the traces on the MCPCB, if that doesn't work I will jumper the traces with wires.

RMM, is that current draw measured with direct drive, stock driver, or with the MOSFET swap?

I was very aware of how resistance in the circuit could impact the results, that is why I set it up so as to try and eliminate any possible points of resistance. As you know, it only takes one bad connection to cause a problem.

If that is the case, then it could be the alligator clips, banana jacks or even the cells themselves. Voltage at the pack dropped 0.2V after the 10A draw, so the internal resistance of the 4 pack would be .02 ohm or 20 milliohm. Times that by 4 and you get 80 milliohm per cell. Is that about to be expected for that cell?
I am pretty sure that XM-L2s will draw less than an XM-L with 18650s in direct drive. But you are right in expecting much more, so was I. That is why I immediately suspected the traces on the MCPCB.

The light is back together, I will try a test later with nothing but solder joints at ALL connections, even the meter. With the driver in place if the current goes up, then we know.

Actually, the current draw in the video is slightly higher WITH the driver than WITHOUT. That means something is amiss here. This is a case where if I am wrong about the MCPCB, it would be GOOD news. I would be glad to be wrong about that.

Direct drive to the MCPCB with the stock skinny wires and a single cell.

The 0.2v drop isn't much at all, actually. Especially since those are 4.3v cells which unless I misunderstood you've only charged to 4.2v. Even so, you should be seeing much higher number with that, especially with 16 AWG wires running to the MCPCB. Even with those cells charged to 4.2v I would expect 18A+ out of of that setup.

I have my test leads (a pair of 18 AWG on each plug, not sure if that's still as much as a single 12 AWG but it's enough) soldered directly to the jacks of my DMM (also a red HFT like yours.) I noticed that at 6-7A my banana plugs would start to get pretty warm, so I got rid of them. The only reason I don't try and measure more than one cell is that I am pretty sure it will pop my DMM, I ruined one once trying to measure 4 20Rs into 3 XM-L2s...I need to get a 30A ammeter for these big multi-cell parallel lights.

P.S. (edit) PLEASE don't take anything I've said as an insult. I know that sometimes on the forum it may come across that way, I really don't mean it to. We are all here to learn from each other and I appreciate you posting your experiences.

RMM, I wasn’t insulted at all. Like I said, I am hoping I am wrong.
Just to show you how things go, I am revisiting this post because I just realized my math was wrong. The cells dropped 0.26V, not 0.20. So the internal resistance of the cells comes out to 104 miliohms.

You know it’s funny, that trick about soldering the test leads directly to inside of the meter that you mention, you learned from me. I hooked a bunch of meters into the same circuit.. I learned it from Pulsar13 . I NEVER GOT AROUND TO DOING IT. Shame on me.

If I were to blow a meter, so what? My wife just so happens to be picking up another FREE one at HF tonight on her way home from work.
Hows that for a loving wife. :slight_smile:

Right on! (I also have a few extras laying around.)

Nice test dchomak. I'm sure you addressed this and I just missed it. Isn't the limit on that HF DMM 10A?

Yes, but it will do more than that for short periods of time, I've done 13-14A with it. My first one didn't handle ~20A very well though.

RMM is right, little known fact, it will measure up to 20A but the hardware can’t take the current.

RMM, preliminary results look like you are right about my connections. I am in the process of charging that pack up right now. I will update shortly

Back to the HF meter measuring up to 20A.

Notice all the other scales on the meter start with the number 2. There is a reason for that.
When this meter measures 10A, what it is really measuring is the voltage drop across the 0.01 ohm shunt resistor. Using Ohms law that would be 0.1V. To measure 20A it would be measuring 0.2V, and we know the meter can measure THAT.
It’s using that scale when in 10Amp mode.
Now the reason for all the scales starting with the number 2, it’s called “Benford’s Law”. Here is the Wikipedia article, it is REALLY interesting stuff. Employers can use it to spot fake expense receipts!

http://en.wikipedia.org/wiki/Benford’s_law

OK, the cells are charged up to 4.20V and the head of the light with the driver in place is ready to go. This time all connections are soldered including the connections to the meter. The leads are 14 gauge and are soldered directly to the banana jacks inside. Also the wires to the cell pack are soldered and the connections to the driver are soldered. There are now NO banana plugs or alligator clips to introduce resistance because of less than perfect connections.
Cells sitting at 4.20V and the light is not yet turned on, 0.0A.

Now on high, 13.75A, 2.3A per emitter.

Wow that is a lot of juice! So let me see if I got this right:

$23 Flashlight
$ 1 MOSFET
$ 5 Batteries
$29… Now that is one Value light! Wonder how many lumens/$?

**Received mine today. Its my first fatty :slight_smile: If my multimeter is correct, it draws 7A on high and 2.7A on “low” from 4 freshly charged panasonic laptop pulls. The quality, look and feel is superb for the price.

Thanks for the info RMM and dchomak. So you take your readings before the shunt starts getting too hot. Makes sense.

dchomak, Great info on the resistor, voltage, and Benford's law. Looking forward to reading that Wiki you linked. Thanks again.

Some here may wonder about the $5 Siskiyou is referring to. I mean how can 4 - Samsung 2800 mAh be only $5? In my case, and others, I have lucked out every step of the way on this one! The battery deal referred to is a NOS $10 laptop battery pack deal that he posted about here on BLF a couple of months ago. 8 Samsungs, new and in perfect condition. Turns out it is the perfect companion for this light, 2 sets of 4 cells. One in the light and the other set charged up ready to go. The deal has expired now but here is the link.

Another benefit of these cells is that they are meant to be “over charged” to 4.3V. I won’t normally be using them that way and neither will most others that picked up on this deal. But I thought I might as well go for it and see what they will push through the light at 4.3V, so I charged them up.

On high, 15.02A

On “low”

Notice that 1/10th of a volt more pushes another 1.25 Amps. The open circuit voltage is not what does that but rather the voltage while under load. I’m sure IMR’s would do even better, as they will not sag as much under load. I have some, but so far I have resisted trying them out in this light. My biggest fear is blowing the traces on the MCPCB

Yes, the low resistance cells will do significantly more than that. A single VTC4 or 20R will almost allow amps than four of those cells, for a little while at least. Four VTC4/VTC5/20R/25R will do around 20A into three XM-L2s, I am guessing that with 6 XM-L2s 25A isn't out of the question with these cells, maybe even 30A.

The nice thing is that you can use higher resistance cells to limit current. The NCR18650B is a good example of this, great capacity but it will only do around 4A maximum direct drive.

What are the odds of ever finding some of these VTC4/VTC5/20R/25R in a laptop pull? That would be sweet! Didn't know they make that much difference in our flashlights versus they panny 3400!