That’s the maths I’ve been doing. As per the above example:
0.73 AH ÷ ~8 (estimated) ÷ 25 A = 0.004 Hours x 60 = 0.219 minutes (~13 seconds)
I’ll reverse engineer the graph so to what current can be sustained 3 minutes.
With some fiddling, about 18 amps.
I was thinking you could get that number just from the math but I deleted my post on that since I think the difference in voltage sag at lower current levels will have a big enough effect to make the math method not accurate enough.
It’s ok. I’ve been doing this for a while now and just ballpark figures do give me an insight as to what to expect.
Strange, the West Mountain Radio graphic uses such an awkward AH scale.
Nevertheless, those QB26800 cells from Aloft (the gold wrapper ones) don’t live up to my expectations. Originally was supposed to be ~10 mΩ IR (1kHz). And they cost me much with the shipping to Canada.
Looking forward to the eventual test with the green and grey wrappers. I would like to contribute but these were above my paygrade ($54 / 2)
Ah is the industry standard so it’s the default for most testing. They allow plotting by run time or Wh though.
But all this analysis gives you an insight into what we flashlight enthusiasts have as current capacity, that’s to say below ~3.6 volts isn’t worth considering for a power-hungry LED. And they have some at above 30 A !!!
Have to add, I bypass the FET driver for such high demand – hardwired direct drive, single-mode ON.
Sorry to hear they didn’t work out!
No good boost regulators to help out with that?
Hmm…actually, there would be a decent chunk of heat to deal with using that regulator and I bet you’re already dealing with a lot of that from the LED.
I like that bypass solution.
Part of the exploration costs. Others in that build and 100+ sank in. Put aside till I find a better cell or lower Vf emitters.
Just now Simon (Convoy) is developing a power boost driver. I’m in line for a few…
Heat isn’t a problem if there isn’t a thermal cut-out. I live in a cold climate and use work gloves with these lights. I do check on the tube heat – wouldn’t want a runaway battery.
And my builds do consider the wattage. This one is above 1 kg.
I’m thinking Vf is about as low as it will get. At least for remotely affordable ones. The cells will probably be a better option but none will give you want you’re looking for I think. Three minutes at 25A above 3.6V is about 4.5Wh of energy…that’s a LOT.
A super-efficient boost circuit might be the best solution. Anyone working on that?
Oops, you mentioned this while I was composing.
Perhaps I should be building with multi-cell hosts….
Just tonight was looking into a 3x21700 model from Simon. See if he would sell a hollow shell as a host.
As an end note, that P45B would be a good cell for the aforementioned build. Inferring from your discharge graph, could sustain 25 Amps for 2 1/2 minutes. Looking forward to the availability this autumn.
Run time would be easier for my needs. I don’t know about the other members. But you confirmed my understanding of the graphs.
Perfect circling back around… 
Agreed, looks like that would end up at a bit over 3.6V.
Yea, I can see how run time would simplify things…direct read, no math needed.
If there were a bunch of requests for a particular re-graphing I could do that. Too many different individual requests each day otherwise. My patrons can request re-graphing though.
Mooch,
It’s nice to see you here and thank you for your work. Thanks for giving us this data! The cell looks really good!
Nkon says they’ll have it mid July : Molicel INR21700-P45B 4500mAh - 45A - 21700 & 20700 - Li-ion - Rechargeable batteries | NKON
Nearly double the price of P42A though 
While this seems expensive in comparison with P42A, it’s still cheaper then buying a P42A, 30/40T in a walk in Vape shop or electronics store, at least here in Europe.
Vape shops are always way more expensive that online, but shopping Costs eat into any discounts that way. It’s still mighty expensive and competitive with the Samsung 50S.
*Destroys the 50S in cycle life and high power performance.
Hey Mooch, thank you for all that you do for us. Been following for years. I noticed you got the P28a cells you tested from 18650batterystore, but I got some really bad ones from them($300 worth). Ink shade and even wrap totally different than picture on brand new cells that were just released. Also, they weigh 1.2 grams less than Molicel cutsheet (44.83 Grams instead of 46 Grams) Also, the Samsung 40t cells I got are self discharging like crazy. The can also seems way different than the 30T can on some authentics I have. Almost as large as the Purple Lishen LR2170LA... Wondering if rewrapped. I noticed the only authorized distributor listed on E Moli One website is Liionwholesale. What do you think of this vendor and why do you think their are cells $1-3 dollars cheaper than liion, imr, illumn and so on?