Because lumen brightness is low (600lumen for K9.3 / 9 led and 900lumen for E12R/12), I use lowest value on the chart per led which add up to about the correct total brightness:
E21A is 2.63V at 150mA
219B is 2.72 at 150mA
so I multiply by 2.63/2.72 and I get 34.6% more efficient for buck driver. I think most likely this is very simple estimation and not accurate, but even if it is different by +-10%, the effcieincy for buck is clearly shown in this comparison. K9.3 with buck driver would be amazing!
Thanks for your comparison, clientequator, that’s exactly what I would like to show. The efficiency of a buck driver is much better especially when a low Vf emitter is used and driven with low current.
My lumen numbers may be inaccurate, especially when it comes to a light with multiple emitters like this. I’m using a “lumen tube” for easier measurement, but its result is not that good for such kind of lights. I just calibrated my E12R results with maukka’s standard light (219B) and updated my E12R charts accordingly, and these results are now a bit lower (~7%) than earlier. Probably still inaccurate though
Hats off and thank you so much toobadorz for this detailed analysis. I took the liberty to summarize your observations and link to this thread on „the other forum“. ;-) Good to see some actual efficiency comparison between linear and buck drivers. :THUMBS-UP:
I personally prefer the E12R charger, because it ends with a lower cut-off current, leaving the battery quite close to 4.20V. The trickle charge phase for taking care of a low voltage cell is also quite good. The total charging time actually varies and is related to the cell and its voltage before charging (I own 2 pcs of K9.3 and 6pcs of the new Fireflies lights, all tested), so simply regard both of them as ~3hrs charging time.
Since the K9.3 is a switching charger, you might want to see what it output not want it inputs, since it is essentially working as a buck charger from 5V input source, so that means input current will be lower than actual output current, would be useful some output measurements rather input measurements.
Also would have been nice to see the “guts” of the E12R not only of the K9.3 in such massive amount of detail.
I believe both K9.3 and E12R utilize a buck charger, because they both consumed 4050mAh~4150mAh from the USB power source to charge a 4800~5000mAh cell.
I think I’m going to give one of my 9.3’s to my dad for Father’s Day and replace it. I dig the E21A 2700K on CH1 but I just can’t get into the CH2 W1 Yellow (Osram KY CSLNM1.FY)
Not sure what build I’ll go with though. My other two 9.3’s are
Been a few weeks since I visited this forum, looks like we both felt the same way on CH2 yellow. Mine ended up selling though a facebook group, hope the new owner is enjoying it more that I did.
I really enjoy the CH2 W1 green, I think it pairs really nicely with the crispness of the E21A 3500 or 4500 on CH1.
Ooo! I like that idea too. I only have 2000K and 2700K E21A’s. The 2000 is my favorite indoor tint but the 2700 is too warm for outside for me. So the 3500 you think?
I’d love to see that build myself! I have one light with the E21A 2000K which is awesome for indoors but too warm for outside. I have another with the 2700K and it too is a little too warm for my taste. However, I have a D18 with an even mix of SST 2700 and 4000’s and it’s awesome.
It’s too bad Hank doesn’t seem to have this emitter as an option because it’s powerful and a really nice tint
If you want to get the best tint, best color rendition, best proportion of red in the light's spectrum - pick E21A. The maximum output however is significantly lower than SST20.
SST20 4000K however might be a good compromise between tint and performance. Please keep in mind that E21A emitters have a low forward voltage, hence a big voltage difference that needs to be burnt into heat by the linear driver. Eventually, you may notice a larger stepdown with E21A than with SST20 as the driver's components need to deal with the excess heat of the mosfet.
I think it would be much more interesting if Hank was to offer XP-L HI 2850K and 4000K again or even XP-L2 4000K 70CRI and LH351D 4000K 70CRI for CH1 on K9.3.
