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.
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!
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.
**Received mine today. Its my first fatty 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.
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!
I don’t know if there is a better thread for this but I just wanted to let you know that DX finally shipped my order of three pairs of protected Sanyos (sku 121447) they had on sale at the same time as the Skyray of the OP.
They are back on sale but now at $11.99. They exchanged the pictures, too.
I just finished the mod of dchomak with the low resistant wires & mosfet I got from RMM (thanks guys!). Also did a tail spring mod with soldering lytze and put more thermal compound between star & pill.
As dchomak already mentioned, the driver is glued in the head and I also had to pound on the driver from the other side to disassemble. When desoldering the wires, I notice the red wire was connected to the L- on the driver. I didn’t remember whether it was connected to the + or - pole of the LED star, so I soldered the new wires + to + (red) and - to - (minus). The flashlight didn’t give a kick so I crossed the wires.
I tried to screw back the battery compartment and the SRK gave an intense bright hot flash so I thought I blew the LEDs to heaven J). In a startle response the batteries flew around the room :~ Didn’t smell bad though, so I picked up the batteries and screwed it on again.
The light started shining, so apparently it was default on. Well, in fact it was SHINING!! My goodness, this is a performance boost, I really felt a powerful hot beam shining on my hands. The body got also quite hot quickly so there must be a lot more Amps pumping around.
In my opinion, this DX SRK is a real BLF champion. Cheap, quite easy to mod, good quality and a powerful lumen king. Highly recommended!
(I also have a few extras laying around.)
