This UI is the result of a collaboration here where everyone was (and still is) encouraged to share suggestions. Alternatively, Wurkkos could have used a simpler UI like Acebeam‘s H60 but it would have lacked some nice, unique features like a direct access to turbo mode or user-defined brightness modes between throw and flood light in parallel use. I agree that HD20 would really benefit from two e-switches. That’s an approach I am pursuing with Wurkkos already, see WK30S for reference.
I think I noticed several firmware bugs, but I haven’t found out how to reproduce them. One time I changed the brightness when both emitters were turned on, but their level was not in sync (meaning the spot was one or two levels behind the flood). When the light is turned off and I double click for turbo, sometimes both emitters turn on, sometimes only the emitter that was used before.
Below is a quote from a post in a different BLF thread that reviewed the Wurkkos HD20:
https://budgetlightforum.com/t/-/63853/33
Thanks Fescron for the tip that while the light is on a "quick triple click" cycles the LED modes in the same way as a "click followed quickly by a hold".
Also, the moonlight mode is only memorized for a second or two on my light. I was testing that when somehow my light ended up in a state that while the light was on I could not cycle the LED modes with either of these two methods and a "hold" on the switch unexpectedly kept cycling the LED modes instead of the brightness no matter how many times I tried to change the brightness. Turning the light off and then back on again resolved the issue but I could not remember exactly what I did to initially cause the issue and have not been able to reproduce the issue.
You’re right about moonlight, in hindsight I have the same behavior! After about two seconds the light’s memory goes back to the lowest setting instead of moonlight.
I got my HD20 today. I want to spend more time with it before giving a review and testing the USB-C functionality against different chargers. But someone posted about a weak headband rubber material that holds the light to the headstrap. That happened to me too. One of the two rings holding my light broke in a similar way.
The light is slightly bigger round than most lights. Will generic headbands fit this OK?
I’m looking for something like this…This one is for dia 28-32mm, the hd20 has dia of 26mm(measured at rings)
I’ve tried holders of boruit D10 and Skilhunt h04, but they don’t fit
Yeah the biggest negative I think is also the headband. If I could get the light in easier I’d be much more inclined to use it as headlamp or handlamp but now I’m more leaning towards “once I get it in the strap I should kinda leave it like that”… I’ve already put it in twice and every time I fear I’ll break the straps, it’s too tight imo 
My personal observations concerning Wurkkos HD20:
User Interface
Unfortunately, Wurkkos did not fully adopt the UI that we originally agreed upon here on BLF. In some details it is noncompliant to the manual I created for this headlamp.
Let me highlight the differences to the UI shown in the manual:
- Unlike stated in the manual, there is no mode memory for the selected brightness per LED when cycling through Flood > Spot > Flood+Spot. The corresponding LED(s) will always restart on Low mode. However, there is mode memory for the last-used setting when you turn OFF and ON again. That's not an actual problem but it may be worth improving with batch #2.
- The moonlight mode has a glitch in the first 5 seconds. When turning ON by pressing 2s it turns on in moonlight mode. When turning OFF and ON again within the next 5 seconds the light will still start again in moonlight mode, i.e. moonlight mode is temporarily part of mode memory (unlike intended). Normally, mode memory only works for Low-Medium-High, not for moonlight or turbo. Again, nothing to worry about but worth considering for improvement.
- Unlike stated in the manual, HD20 does not always use both LEDs for turbo mode. Instead, it uses the LED mode for turbo mode that was selected before. For instance, if you used spotlight only, a doubleclick will use turbo mode for the spotlight LED only. The other LED will remain off. The same applies to direct access to turbo mode from OFF. In order to have both LEDs activated for turbo mode you need to select Spot+Flood mode before. This is the most significant difference to what's stated in the manual. I do not know if it should be kept this way as Wurkkos always wanted to use both LEDs for turbo, regardless where you start it from. To my surprise, all strobe modes work exactly as stated in the manual, i.e. HD20 always uses both LEDs at the same time, regardless of the selected LED mode.
- Unlike stated in the manual, the LED mode can also be cycled by a tripleclick, not only by 2H (click, click+hold). This is actually quite useful but it's not an official part of the UI.
- There’s a nasty random glitch in the firmware when using both LEDs (Spot+Flood). Sometimes when cycling through Low-Medium-High the LEDs are out of sync. That means brightness of each LED will not cycle upwards in parallel but randomly between Low, Medium or High. I did not find out yet how to reproduce this glitch - it just happens every once in while.
To be fair, none of these noncompliances are serious or render the UI unusable. I will try to post a separate, rectified manual for batch #1 lights. You may want to exchange your original manual by the rectified one.
I made a short video about the general UI behaviour when cycling LED modes or brightness modes.
I also made a short video of the UI glitch in Spot+Flood mode. Another BLF member reported the similar glitch before.
Powerbank mode / Reverse charging
I tested this feature using an USB-C to Apple Lightning cable to charge my iPhone 6 Plus as well as a 100W USB-C type C-C cable to charge my Xiaomi Redmi Note 8T. The iPhone would not charge using the HD20 as power source, only asking once to unlock for using the "accessory" and then doing nothing anymore. The Android phone however was charged by HD20 (at slow charging speed). This observation underlines that there seems to be an encoding problem between the USB-C specifications and the (reverse-)charging protocol of HD20. Many smart chargers seem to be incompatible with HD20 when using type C-C cables, probably when asking for 9V, 12V or 20V output voltage. But there seems to be more to it and only closer inspection on Wurkkos's side can resolve this issue.
This actually sounds like an improvement and i did suggest this in the UI planning.
That was probably me. Here’s my video:
There is also another bug regarding turbo. If you start from spot mode, turn off the flashlight and wait more than five seconds, it will enable both LEDs. Before five seconds it’s just the spot LED. This does not work with the flood LED.
Yep, same with my sample. As soon as Wurkkos is available again, I will send them a summarized feedback.
Strange, I don’t have those problems with mine, done several tests.
Looks like not all of the lights have these bugs
Yeah I also like this “feature!
Ah yes memory mode throuhout flood/spot could be useful IMO, I’d use spot on low - flood on medium for example.
I suppose one could also call this is a “feature”? Suppose you turn the moonlight mode off but you need it again fast, just one click away instead of holding…
Yeah this clould also be called a “feature” I think, I sometimes like to put only flood/throw on turbo. However it’s always nice to have quick access to real turbo with both LED’s, so I’m not entirely sure what I like more…
I really like this “feature”! I almost never use 2H, 3 short clicks is way faster!
Ah yes I noticed this when testing it but thought it was related to the memory modes, I haven’t seen it happen recently though…
Huh my android phone seems to charge fast and I can also charge the HD20 with a Baseus 65W charger and a Type C - Type C cable…
That’s weird, mine does some strange things when using 18650 VTC6
I always used 21700 LG 10A before…
Maybe because of the higher currents of the 18650 the lights acts different?
What type of batteries do you guys use?
What strange things?
Btw just hooked up the scope. PWM on all levels except turbo, 20 kHz (!) and when both LEDs are active, the spot LED turns on 15 μs after the flood LED. And the strobe mode makes some nasty audible noise from the switching.
Sadly I don’t have a clamp meter here at the moment to measure the current.
Mine definitely has a couple of these “bugs”. It still has important long hold-click to moon, double click to turbo. Its only in the trying to operate the leds independently I get strangeness.
My headband is useless. The two loops are too thin. One of loops came damaged and it means that I can’t use it as a headlamp.
The 5000k beams are absolutely beautiful. Independently and together they have no green or yellow tint, and look great.
I could not get mine to charge c-c, could not get the power bank to work, though I am still testing
Both LEDs went on(clicking from off) while last time only 1 led was on and I didn’t came from turbo as others did.
For my chargers with USB-C ports that would not charge the Wurkkos HD20 with a USB-C to USB-C cable, I used the following USB-C to USB-A adapter with the adapter plugged into the USB-C port of the charger and a cable with USB-A to USB-C connectors plugged into the adapter and the Wurkkos HD20. The adapter is uni-direction and the adapter's USB-C connector must be plugged into the USB-C port supplying the charge to work correctly.
This is the adapter I used:
I was hoping the same adapter plugged into the USB-C port of the Wurkkos HD20 and cables with a USB-A connector on the adapter end would allow me to successfully charge devices using the HD20 as a power bank when cables with USB-C to USB-C connectors or cables with USB-C to Apple Lightning connectors would not work.
However the Wurkkos HD20 USB-C port is not working very well for me as a power bank with either method.
I have not been able to charge any of my devices with Apple Lightning ports using a USB-C to Apple Lightning cable or with the adapter plugged into the HD20 and a USB-A to Apple Lightning cable. I have been able to charge a few but not all of my devices with USB-C ports with either just a USB-C to USB-C cable or by sometimes needing to use the adapter plugged into the HD20 and a USB-A to USB-C cable. I can charge all of my devices with Micro-USB ports using the adapter plugged into the HD20 and a USB-A to Micro USB cable.