Skilhunt E3A (AAA twisty) - First Look

Thank you, gchart!
Coming from a non-technical background it’s a bit hard to understand where all the energy went to… In case of alkalines, Duracell Coppertop AAA can deliver 0.5 W constant power for over an hour. Practically every LED light bulb manufacturer reported that their fixtures passed 200 lm/W threshold. Bare LEDs passed that like 8 years ago. So, one hour of regulated 100 lm on one AAA alkaline element should be common place by now, right? From the chart it seems like we get a quarter of that. Where did all the energy go to?

Yup, saw your comment about resistor size earlier in this thread. I only have 0805 so will try that first otherwise looks like I’ll be ordering more parts :blush:

Not without replacing the driver. This is single mode only with no potential for having two modes.

The higher the current draw, the less apparent capacity. Especially for alkalines. NiMH have better discharge characteristics for higher current draw but there’s still a limit.

In looking at this chart in the Duracell AAA datasheet you linked to…

You can see that as draw goes up, capacity goes down drastically. In stock form, this driver is dialed in for 221 mA current to the LED. With an LED vF around 3.0 volts, that’s 663 mW. There’s some inefficiency… let’s say the boost driver is 85% efficient. That’s a total power draw of 759 mW. According to that chart, it shows to expect around 1/2 hour of service life at those kinds of power draw.

Resistors are small. Solder one in place, attach a second one in parallel with thin enameled wire, with a contact that can be switched somehow. Must be integrated in the plastic holder.

There are lots of 80%s in there.

The ’351 is rated about 170lm/W. Optics might have roughly an 80% efficiency (ie, 100lm from the LED = 80lm OTF [out the front]), the boost driver might be 80% efficient, etc. Losses add up.

Also, internal resistance goes up as a cell drains. Terminal voltage drops, to the point where the driver can’t keep supplying current, hence it dims and eventually turns off. The more current you suck out, the lower the terminal voltage.

I just burned down an alkaleak last night supplementing some light when reading. My E03 still had all 3 modes, but M was almost indistinguishable from H. Turned it off to flip through pages. Next time I tried turning it on to read something of interest, it wouldn’t turn on. Left on, it could’ve burned lots longer.

Point being, alkaleaks are pure evil. They do things just to screw with us and cause us misery.

Thank you for the explanation, that’s about the level I can still understand :slight_smile:
The LED has efficiency of about 100 lm/W then, right? That accounts for one half of my inflated expectations. So, we should expect 0.5 hour of fully regulated output. We are getting about half of that, if I eyeball it correctly. And we have already factored in driver inefficiencies (85) and the actual power draw of the LED. What does that mean? The driver is actually 43 efficient? Or the element is not quite Coppertop quality? It feels like we are being shortchanged at every turn :slight_smile:

This is another important piece to keep in mind… I didn’t have any brand-new batteries to test. My alkaline was partially used.

Here’s Skilhunt’s chart. It probably pretty close to reality.

And yes… there are inefficiencies everywhere. Increased power draw decreases battery efficiency. The driver has some inefficiency (roughly 85% or so). You’ll lose some through the optic (~15% loss). It all adds up unfortunately.

The constant power discharge graph already accounts for that. Right? Falling voltage, rising current - it’s already there. When all is said and done Duracell promises you 750 mW for 0.5 hour = 375 mWh. Or, if you can lower you consumption rate, 500 mW for 1.1 hour = 550 mWh

It doesn’t look like like it’s 85. The LED consumes 221 mA at 3 V = 663 mW while in regulation. Once the light output drops I assume the power used drops proportionately, so I completely unscientifically integrate total power (663 mW * 5 min + 330 mW * 20 min) = 165 mWh. If we assume driver efficiency at 85 it’s 195 mWh out of the battery. So either your battery was half discharged (but then it wouldn’t measure 1.55 V) or the driver efficiency is about 50%.

I know even less about optics than I do about electricity, if that’s possible :slight_smile: Let’s ignore that for now.

Thanks Gchart! Awesome data!

I did some crude and quick tests of my own E3A tonight with stock resistor HiCRI version with a bench supply and my eyeballs… I’ll likely do it again at a later time with more equipment and effort…

From off (sweep up), turn on voltage on my sample was 920-930mV. Once on, LED didn’t go dark until 0.13V!! I didn’t expect that!

From 1.4V down, I saw min input power at 800mW which increased linearly until about 1.25V ( Peak input wattage happened at 1.03Vin (1160mWin) after which power began dropping quickly. Heres the raw data in Vin mWin. Laptop is dying… edit later

1.4 0.84
1.35 0.85
1.3 0.87
1.25 0.9
1.2 0.92
1.15 0.97
1.1 1.02
1.07 1.06
1.04 1.1
1.02 1.16
1 1.09
0.97 0.99
0.94 0.89
0.91 0.79
0.85 0.59
0.8 0.46
0.75 0.34
0.7 0.23
0.65 0.14
0.6 0.07

Or, to put it visually

Thanks for that, I’m very much a visual person. So in the primary operating range, it appears to range between 800-900 mW. Certainly explains why alkalines really aren’t a great fit and that NiMH & lithium do much better.

If I’m honest with myself, idk if I’ll get back around to more measurements with this light this week. But I’ll clean up the post and data from my PC tonight. Thanks for posting that plot in the meantime Don.

Gchart, I agree that at stock output, alkaline is only compatible technically. Though in the 2.3 lumen mode and now seeing how far down this boost driver operates, I can imagine some crazy runtimes… And leak prone cells

Is that to be expected from a $10 flashlight? Or there are no boost drivers with >90% efficiency in 0.8-1.8 Vin range regardless of how much the light costs?
Thinking way back, my Walkman was able to suck two AAs dry in the late 80s, so it should be possible. Maybe not in a flashlight form-factor?

It’s all about the power draw. That’s just a lot of power to ask of a AAA alkaline. If the output were lowered a bit (like in my 42 lumen test), I imagine the alkaline would respond much better.

It’s hardly cell’s fault that the driver draws 1160 mW just to pass 663 mW to the LED, is it? It was doing it to the bench supply.

Took some comparison shots with some of my AAA flashlights. Not enough to open a new thread, hope that’s OK for you.













oooh, i actually been eyeing the edc01, cant believe its significantly bigger, hm…

edc01 (new worm), is a 3 mode light, arguably more versatile, and batteries can last longer

The E3a comes on at a brightness, 90 lumens, that drains an AAA in 30 minutes… to me, that is a waste… but its the smallest, lightest, highest CRI aaa option, if someone wants a keyring light for example. I personally choose not enlarge my keyring. My lights are easier for my use, separate from my keys.

the edc01 is rated to go 4 hours on its medium of 30 lumens, plus it has a 5 lumen low, plus a high that matches the E3a… however, there is NO High CRI edc01 option.

to get High CRI aaa, another option is the aaa Tool from drop.com… comes in fancy metal too… $lippery

so, for simplicity, the tiny E3a, with high CRI, is king of the little light Hill

try them all, then decide :money_mouth_face:

But it runs 60 minutes on an AAA. :wink: