Great work, thank you for sharing!
Interesting to see how inefficient the SC53 is compared to the other Zebralights that were tested.
Skilhunt H04 offers very good value.
Efficiency on the E12R and SC700D is the reason I always buy Buck or Boost lights 
Zebralight H600c/d mkIV
Uses the TPS61088, synchronous boost converter with integrated switches, set at ~700kHz switching frequency, ~6V output.
Coilcraft XEL or XGL 4020 1uH inductor, 14.6 or 9mΩ
I couldn’t find the ref of the RPP PFET, but like in the SC64 it’s a 2x2mm package, 13~17mΩ.
Note that this is the driver only, the H600 series have a very high resistance negative spring around 50mΩ which substantially lowers the efficiency on high modes.
Thanks, nice info.
Wow the Fireflies driver is impressive! I’ve been using the Nov-MU on a daily basis and absolutely love it. Too bad they seem to be having difficulty sourcing components for the driver for the past year.
It’s pretty good yeah, what is disappointing is that there not enough input capacitance and when a higher DCIR cell is used like a 50E or an older cell then the output can be unstable, which when it’s pronounced will lower efficiency, output and generate noise which several people have reported, it does it with my P42A that is not even that old.
It uses the amount of capacitance suggested in the datasheet (2x 10uF 0603) but in my experience of building drivers the suggested input capacitance for buck converters is usually not enough.
I added more caps, two 10uF 0603 stacked and one 0805 22uF farther away by removing some solder mask, but I haven’t reassembled it yet to fully test it.
Another (small) issue is the max current of 5.5A, the traces resistance on top of the sense resistance were likely not taken into account when deciding on the Vsense.
This data is really interesting, thanks for providing it. Seems like the E12R and SC700 do quite well. Do any of the other ZLs have the same high resistance negative ground spring issue, or is that just the H600? Does SC600?
SC64w HI also seems pretty decent. Do you know how SC64c LE would do? I wonder, since I would guess that would be a 3V buck or buck/boost, in contrast to the boost used by the other 3 models here.
Why do you think some of these drivers have lower efficiency than some of the driver designs I’ve seen around here on BLF (such as yours)? Are there particular design limitations involved for these companies?
Any chance you have and could test the timeless Noctigon Meteor M43 flashlight driver?
hm
all that means to me is, i might need to charge in 8 days vs 8.34. with one light vs another. sometimes. if the LED efficiency doesn;t invalidate the driver efficiency…
?
wle
thefreeman, thank you for this!
Seriously great topic, thefreeman! So fascinating to see how efficiency changes across the output selections. I’m impressed at how well the Skilhunt H04 does. In my anecdotal experience with my H03, I felt it was an efficient flashlight based on how long the battery charge would last with usage at a variety of brightness levels. The Zebralight is SC64c LE is rather disappointing… I’d been under the impression that it’s a nicely efficient design. I’m tempted to do a crude head-to-head test of mine with a few other 18650 flashlights all running the same 18650 cell spec, and see how it does.
Thanks
I haven’t tested the SC64c LE (3V), only the SC64 (12V), the former will likely be more efficient, I’m not sure what is exactly the issue with the TPS61088 used in the SC64 but the efficiency drops at 12V output, boosting to higher voltage (12V vs 6V) is a bit less efficient but not that much.
The H04 is in my opinion not very good, it only goes above 90% in dropout (i.e not stepping down the voltage), they’re cheaping out on components : high resistance path (about 220mΩ) and asynchronous topology.
I could if I had it 
The SC600 III/IV and SC700 have pogo pins, I don’t know which part exactly they use but similar pogo pins from Mill-Max have a max resistance of 20mΩ, and with the amount of them the total resistance should be quite low (6 in the SC600IV for example = 3.3mΩ max)
The SC64 does have a thin steel spring like the H600 but there is one less spire and maybe they touch themselves when compressed, in the the H600 spring doesn’t compress a lot with unprotected cells, in practice the tailcap can get quite hot in turbo with the H600, showing that a significant amount of power is wasted, but it does not seem to be the case with the SC64 (but it also draw a bit less current so…).
Personally I bypassed the spring on my H600s, virtually eliminating the resistance.
I haven’t disassembled my SC64 LE yet but I will measure it in the future, it’s a 3A synchronous buck driver based on the TLV62085, it should be more efficient.
Regarding drivers having better efficiency it’s mostly about using better components : lower resistance PFET (for the reverse polarity protection), inductor, sense resistor, switching/rectifier FETs, for converters IC they’re integrated in the IC, so it’s about choosing a good converter, and one with synchronous rectification i.e the rectifier is a FET and not a diode (asynchronous).
I hadn’t considered the relative efficiency here; yeah, the SC700 XHP50 rather trounces the H04. That’s sad to hear they’ve cheapened out on components for the H04. I wonder how the M200 series fares in comparison…
Convoy FC40 22mm driver :
I upgraded my measurements setup, before I used 2 Uni-t UT210E current clamps (2+3) , an Uni-t UT139C (0.5+2) and a RDtech ”precision” voltmeter.
Now I measure the current across 0.1% current shunts with a BM867s (0.032), Aneng AN870, Owon B41t and a RDtech precision voltmeter, the 3 later voltemeters are calibrated against the BM867s and are within 0.02.
1 Thank
Are losses in efficiency somewhat linear with output current when using Monolith boost converter? If Emisar/Noctigon driver has 95% at 2A, this has 92% at 2.5A then how probable is it, that this driver would have ~88% at 3A?
Well power losses are not linear (which would mean constant efficiency), a large proportion are conduction losses (I^2 x R), but you can see from my graphs (I should redo them with my new setup) that efficiency points aren’t linear either, but especially I think it’s the temperature increase that greatly increases power losses at high currents and tanks the efficiency, because running simulations without temperature modelisation gives a fairly straight efficiency curve.
Anyhow the Emisar boost driver efficiency is lower than that according to Hank’s measurements :
Which isn’t surprising since the inductor is smaller.
Edit : Vout is also higher.
Oh, it was 95 at 20%.I remembered wrong.
thrunite T1 :
Uses the MP3429, 600MHz synchronous boost converter with integrated switches, ~12V output.
6030 0.68uH inductor
AON7423 RPP PFET, <5mΩ at –4.5V, <6.5mΩ At 2.5V
Rsense = 150mΩ, Vsense = 150mV
The efficiency isn’t as good as it usually is with this converter, it has quite thin traces, fairly high current sense resistor and too low inductance.
Input capacitance is quite low (one 0805 capacitor), I had to add a bulk capacitor for making the measurements as it didn’t work properly in turbo.
Are there any other major manufacturers or models for small boost converters other than MP or TI?