I just got mine in today also, it’s the XP-L HI V3 1A grey body. I cannot wait for the sun to go down, this thing is so bright. It does get hot very quickly, but that is understandable at this output. I absolutely love the UI, I don’t understand all the drama over it. This is truly my new favorite light, and currently brightest. Thank you for creating this monster!
High-end LED flashlights contain a small circuit board called a “driver”. The battery connects to the driver, which then connects to the LED. The driver contains a small computer chip which has the programming for the user interface and gives you modes. And on some drivers contains regulator chips which stabilize the output and keeps it at the same level even as the battery is drained. the disadvantage of regulator chips is that the peak output tends not to be close to what the LED and battery could actually do if you bypassed the driver.
“Direct Drive” is what happens when you bypass the driver. The battery is connected directly to the LED. This gives the maximum possible output… but you lose all brightness modes and can only run on max power.
The D4 contains one 7135 regulator chip (380 mAh) and a MOSFET. When output is very low (380 mAh or less) it runs through the regulator chip. While not bright, this is efficient and gives stable output. It should maintain the same brightness even as the battery voltage goes down.
In the D4 “direct drive” refers to unregulated output that is going through the MOSFET instead of the regulator chip. This output isn’t bypassing the driver so you can still adjust the brightness, but the peak output through the MOSFET is equivalent to what you would get with true direct drive. However, because this output is unregulated, output will decline as battery voltage goes down. It’s also less efficient than the regulated output through the 7135 chip.
Put another way: “direct drive” is “super-high-output mode”
The direct drive through a MOSFET switch is only less efficient because the emitter is being over-driven so much. When over-driven, it makes much more heat in relation to light and so, efficiency suffers. Typically Cree rates their emitters at 350mA or 700mA, so it’s down there at the regulated chip level that it actually get’s it’s ratings from the manufacturer. Cree also recommends a max drive of around 3A on most of the emitters we use in flashlights, we just ignore that and push them up to twice that or more in direct drive. Yes, this probably reduces lamp life, but if it’s a 50,000 hour rating to begin with and we greatly reduce this estimation through over-driving, well, obviously, we’re still gonna have a working flashlight for many many years!
No drama, just some fine tuning. That’s the idea of a forum. 
Unless you don’t know who last used it, or don’t remember what level you left it at. Then a single click can produce surprising results.
So at the beginning of a session, it’s a good idea to hold to ramp up instead of clicking. This overrides the unknown memory level and sets a new one.
Or, if it didn’t have memory, it could always start at the same level. That level would have to be user-configurable though, and it trades convenience for predictability. No one method will satisfy everyone.
I don’t think there has really been any drama per se… the response has mostly been “good, but it could be even better”. Some of the suggestions have pretty good consensus, like that it shouldn’t remember moon or turbo unless they were manually ramped to. Other suggestions aren’t so universal.
I’ll try to get the ideas people agree on into a new version, but I’m pretty sure Hank doesn’t want a new UI every month. That would be ridiculous. 
So, we’ll see…
Yes, the Q8 UI is similar but better. Tom’s Narsil is basically the full version of what the D4 has.
Thanks for the answers.
TK, Then the Q8 is going to be absolutely fantastic! I’ve never had a UI as good as this is. No instructions are required for ordinary usage. Just grab it and go. And the “other stuff” is out of the way.
TK you’re being to humble. This is an awesome UI. I suppose everything can be improved on, but I would say this is about as good as I’ve ever used in a UI. I absolutely love it. Keep up the great work. Thank you to all involved in creating this flashlight! I can’t say enough good things about it. The only con I have is a pocket clip, so really I don’t have anything negative about this flashlight at all. Thank you again!
+1
Of course everything can be improved upon, but this already is a masterpiece. Just like the FW for A6/S41.
Really can’t fault the 2 D4 lights I have, I love the UI. I know it auto ramps down when it gets hot but shouldn’t it auto ramp back up when it starts to cool?
219C Vs XP-L
It does ramp back up when it’s cooling off. However, it only goes up one small step at a time, and it tries to maintain a constant temperature. Here is a runtime graph of it:
If the stable level is too low, set the temperature limit higher.
Or if you want to see the effect more clearly, let it step down and then hold a block of ice on the heat sink fins (or run it under cold water). It’ll go up, but slowly.
With my newer stuff, it can step back up faster but I haven’t tested yet to make sure it won’t oscillate. Oscillating is annoying.
Mine has the V2 FW and doesn’t ramp back up when cool, it just steps all the way down to about 200 lumens and stays there. Tried submerging it in water and nothing happens even after being completely cool to touch. I wish there was a way to make the temperature regulation dumb, stepping down to a specific level when it reaches the temperature limit.
For an idea what to expect, this shows how the same algorithm behaves on another light… It goes through a few phases:
- First I turned it on at turbo. I adjusted the position of the light a bit at first, which made the graph look odd at the beginning.
- After the step-down, I let it sit untouched for a while with a fan blowing at it.
- Then I took the fan away, and it stepped down more.
- I left it alone for a bit, and it stayed pretty stable.
- Then I touched ice to the outside of the light. It ramped up slowly.
- I removed the ice. It stayed stable for a bit, resting in a pool of its own cold water.
- After the water heated up, it stepped down once and was stable for a while.
- I blew the puddle of water away from the light so it would be dry again.
- It stepped down again, to about the same level it did before without the fan.
- Eventually I turned it off and ended the test.
The brightness depends very much on the light’s environment and its configured temperature limit.
The step-up uses the smallest steps available, so it can be hard to see. It’s much easier to measure with a lux meter or an app like zak.wilson’s “Ceilingbounce”.
Good to know, I’ve set my 1A higher, blinked 6 times after I set it?
The room temp was very cold when I tested the 1A at 5,400 lumens the next night was warmer and I couldn’t get past 4,800
I got a consistent 4,000 for the 219c with Sony VTCA5 and 3,800 with VTC6, which is on par with reviews. The 1A is far more erratic, even the same batteries yielded different readings.
> UI every month
I’m starting to wish the drivers had an interface for a micro-memory card to accept the updates.
Because this stuff just keeps getting better.
Firmware, that’s the ticket… flashlights with firmware! 
Simply plug in the micro USB and reflash the firmware directly from the computer, like a DSLR.
Precisely mu thoughts from today…include USB type C plug. Use it to:
- reflash the chip
- with a helper app, provide GUI configuration
- charge the battery
- turn the light to a powerbank
As to predictability, the light has better memory than I do. I often avoid turning it on with a single click and loosen the head before that, just in case it’s on turbo.
Also, I never know what direction will the ramping go.
That requires a much more capable MCU than we’ve been using for flashlights. An atmega chip can do it though.
There was an arduino-based light a few years ago, but it was expensive and kind of meh. There was also one with bluetooth for configuration, but it had physical design problems and the concept was never developed very far. Some recent driver designs use vias for programming pins so it can be reflashed acupuncture style without removing the driver, and requires no host modifications. That might be an idea worth exploring further.
That’s why I used different ramp controls in newer UIs. Hold to ramp up, click then hold to ramp down.
I made a reversing one about 3 years ago, but the way it often went the wrong direction always bugged me. So I had been meaning to change it, but I didn’t really touch e-switch code again until recently.
Can you buy tail caps separate? I’d like to mod one to fit on my keychain.
Just changed replaced my 3D Xp-g2 emiters with 5D’s. Man this tint is nice! Perfect light now.