Contact resistance, bypassing traces, and parallel FETs are the heavy hitters (i know you know this). I wonder how much can be gained by increasing contact area with the cells and higher pressure. What is RTSon for that FET? 20cm of 18awg is about 4mOhm. So 2mOhm is about all you could save there in practicality.
Wondering bout parallel FET's - thought that was a bust? I thought maybe TA tried it and got no advantage? I even thought it could do worse, maybe a timing issue? This is very fuzzy with me, can't recall where/when/who. The HK90 has places for 3 in parallel, populated 2, but I replaced the 2 with one SIRA20DP. Think they had older Infinions in there.
Don't assume too much with me - yeah, some things I know, but not everything for sure
Issues with parallel FETs can arise at low duty cycle and high frequency AFAIK. But at WOT in turbo, parallel FETs can only reduce resistance. But with the FET you are using has an RDSon of about 0.8 milliohms. This is 5x less than your wires.
So between the wires and FET you have about 5mohm. That accounts for about a third of what I’m spitballing to be your total. Don’t know how much the traces on the driver, mcpcb, and tailboard are contributing. Bypassed blue springs are about as low as you’ll practically get. That about it. Short of bypassing the driver and getting a comparative lumen value idk what to suggest that isn’t radical.
The battery itself is a factor as well, I would think. Sounds like I should have tripled up the SIRA20DP in the HK90. The K1 SBT90.2 actually has 3 springs because of the USB-C charging - I bypassed all 3 but dunno what the path is through the charging circuit.
I gotta check my other SBT90.2 lights, specially the 2 zoomies 1504 and B158. Dunno but maybe the switches are a high resistance source, but taking an amp reading with the tailcap off.
Yes, the cell contributes a whole lot, but here I’m starting with the voltage under load of a 30T based on HKJs data and reported Vf values from djozz and other’s. It’s seems safe to me to estimate a 300mV drop is occurring at 20A elsewhere in the circuit. The FET doesn’t seem like a meaningful contributor according to the spec sheet.
If you can, check output of mechanical switch lights with your bypass and compare with tailcap installed. These could show a large difference at times. Those that do though don’t usually last that long.
And those amp draws look more in line with what I’d expect. 5-10 milliohm is typical for a good FET light.
I really think it might be a Samsung 50T, which I don’t know if it actually exists, but we historically were slow to learn of these new cells. One thing I’m hoping for is the ‘s’ line of Samsung 18650s (or even an ‘r’) to make it to the 30 series. I think by now there is room to improve power density and maintain 3Ah
I know this ^ was a while ago, but I want to put one in a light that came with an xhp50, what did or do you use for “centering ring”, or more specifically so the reflector doesn’t short out in the mcpcb? I have been thinking about cutting a thin piece of plastic just so the reflector has something to sit on, would that work?
In what light? I had a few lights that had the Gen1’s 90/70’s in them that I salvaged from older lights/builds… In the FT03 I didn’t use a centering ring… I used Kapton Tape to cover the mcpcb from shorts…I was using the MTG2 26mm boards until Hank came out with the 32mm….
His tests were not done in a lamp/flashlight. They were done in a sphere measuring the raw led with a power supply.
In a battery powered flashlight with it’s added losses (let’s use a conservative 20% loss) you would need 5000 total lumen to get 4000 out the front of the lamp. That would be about 18 amps. Then you need to consider the voltage sag. A decent 21700 might sag to about 3.8 or so. 3.8 x 18 = 68.4. So I would estimate about 70 watt is what a flashlight would consume.
If your talking about a raw led powered from a power supply, you can see that 4000 lumen draws 12 amps at 3.15 volt. Thats only about 38 watts. These not very practical numbers for real world use.
Personally I’d estimate a 30% loss and say you need to push it to 20 amps and you might be lucky to get 4000 lumen out of a flashlight.
These are all my own estimates based on djozz’s test results, as I haven’t ever used or measured this led. Maybe someone who has tested it in a flashlight can give some more detail.