Skilhunt E3A (AAA twisty) - First Look

Here’s a quick comparison between the Sofirn C01 and the Skilhunt E3A, both in orange:

Very nice, thanks for the pic

Good thread everyone, and particularly thanks to gchart for the resistor change and the runtimes. Is there any chance of a runtime with the 1 ohm resistor (43 lm) and an alkaline? I think that is worth testing since part of the point of an AAA light is to run on alkalines if you have to. I wouldn’t go past 2 ohms (20-25 lm) since it doesn’t seem worth the hassle compared to using a $4 Sofirn C01 at that point.

I do like that the pill is easy to get out of the E3A and to reprogram (change 1 resistor). Does anyone think the non-potted pill will affect ruggedness and reliability? The Sofirn is potted, which seems like a plus for shock resistance but a minus for moddability.

To the person who asked why the converter isn’t more efficient: in principle it could be made that way, but it would have to either run at lower current, or use bigger parts. It wouldn’t surprise me if it does better at 100mA output than 200mA.

FYI, the original single-mode Sofirn C01 was potted. Some of the current production batch of the C01 are potted, although Sofirn had previously stated they were not going to pot the current batch due to the difficulty of doing so in a light with such a low price target.

As far as I know, none of the multiple mode C01s are potted.

I previously posted a comparison chart here to help people understand the different versions of the C01 family:

Thanks iamlucky13. I think I remember seeing that chart before. SammysHP’s photo of how much smaller the E3A is than the C01 has sort of made me lose interest in the C01, at least the white-led model. This is sort of unfortunate because I have 5 total C01’s on order (2x red, 2x white, 1x C01S) but at least they are cheap. I will order some E3A’s pretty soon, I expect.

I didn’t realize potting was difficult: is it not a matter of glopping some epoxy onto the circuit? I might try doing it.

I have a few other old 1AAA lights such as a nice brass Peak prototype with an absolutely awful 5mm led that sticks out past the front. I wonder if I can transplant the circuit from either an E3A or C01 into it.

If you’re up for just swapping the LED in a few lights, check out this thread and grab a pack in your favorite CCT

Potting… I mean, it’s not rocket science. But the C01’s potting was injected into a hole on the battery side of the driver after the light was assembled. I’m sure that’s a bit manual and tedious. And I think I remember hearing stories of people receiving lights with uncured potting leaking out of the driver cavity (got the mix ratio wrong for that batch?). I’m sure many C01 (potted or unpotted) can take a beating. I have a few and have only had problems with one - one of my kids must have hit it just right and the inductor snapped in half. That has to be a rare occurrence, but probably the most susceptible component. In a Mouser order with some other stuff, I picked up another inductor (of the chip variety this time) for $0.20 and had it functional again in a matter of minutes. No biggie if you have the tools to do so.

Somehow the e3a and older i3e have great runtimes-flat, and longer than other aaa lights with nimh. Im not sure about the high cri runtime though. But that size paired with longer runtime at ~90 lumens for (close to 60 minutes if I remember correctly?) makes it stand out beyond the competition. However, I don’t own one only because it’s single mode. If it had a mode driver it would be king of single aaa lights in my opinion.

The runtime most likely will stay the same. Same current, less efficient, thus slightly darker. Maybe 90 instead of 100 lm, but still 60+ minutes runtime.

There are certainly other similar lights with multi modes. Single mode is one of the attractions of this light, it seems to me. I just wish they’d offer an E3AL versioin where the drive current is set a little lower, by changing that resistor. I really like that driver chip, which I didn’t know about before. Single cell lights and commodity batteries have always been my favorite. I’ve always kind of wanted one of these, though not enough to pay $50 for it:

Now though, maybe I can transplant the E3A driver board onto a D cell holder of some sort.

Hey SKILHUNT are you here? Do you think you can sell us some bare driver boards? I’d buy several, to upgrade other old lights with, among other things.

Gchart, yeah I know about that LED thread, but shipping charges from AU make it painful.

There’s not much magic involved building a simple boost circuit, especially if you have enough space.

True for the D light, but 1AAA is rather tiny. There is also the hassle of getting components. If I need some code than does X, I can either download it or write it myself. But if I need a 1 cent SMT resistor I have to order it from someplace and pay $6.50 shipping because the electronics stores have all shut down.

I was somewhat into electronics as a kid, but I think it’s a lot harder now because of this issue. It’s hard to make anything without having a good inventory of parts on hand, because even if you try to order everything for your build ahead of time, you keep finding that there is someother little thing you need.

Yup, it’s the PAM2803 or a clone. Been around for ages and in many common lights (pretty sure even the Lumintop AAA lights use it). There are even BLF designs going back years ago that used this chip. Multi-mode versions with this basically swap out the current sense resistor using small FETs driven from a SOT23-6 MCU (link)

Single-mode layout is super simple too:

Wow, that is interesting about switching the resistors in and out with FETs. I was aware of programmable resistors like the DS1841 but that didn’t seem so suited to the application. For a very low moon mode maybe it’s possible to have an MCU pin switch a series resistor in and out in front of the led, so when switched in. Any idea what the max voltage is that can come out of that boost converter, or could it possibly fry itself if it sees too high an output impedance? The E3A must have a fairly large inductor that I imagine could cause a big voltage spike. Maybe there could be a parallel resistor also switched out. That might need another FET, but having 2 levels instead of 3 would eliminate one. I guess modding an E3A this way is not really feasible.

I suspect that MCU is something like a Padauk PMS150C that is much cheaper than any PIC or AVR that I know of:

Ordered one E3A from, $9.80 base price, high CRI led and slate blue ano added $1 each so $11.80. Then $6 shipping since order was below $49, so $17.80 total. I guess it might have been slightly less through Aliexpress but I’m just as happy to buy directly from Skilhunt. Aliexpress reminds me too much of Amazon sometimes ;).

It’s $7 from Aliexpress. :wink: At least I’ve ordered one for that price few weeks ago.


Beats waiting 6mos and still paying out the wazoo or any other orifice for shipping.

Ehh same $12.90, maybe a couple bucks less for shipping and less waiting, but with less of the smelly feeling I get whenever Bezos is involved with anything. I’m not in a hurry as I have tons of lights to use before the E3A gets here.

Does anyone know a board like that suitable for bringing less power to the led? Like maybe 3mA, for a button cell light.

Goggle “vampire” on the site. People were doing exactly that.

Thanks Lightbringer. I looked at a bunch of vampire threads and I did some studies like that myself on CPF some years back. But that idea is to get every last bit of energy from a depleted battery, running the led at super low levels (like below 0.1 lm) that are still surprisingly usable. What I’m hoping for is a bit different, running the led at fairly low level (1 lm) even on a full battery, to decrease the drain on small batteries (coin and button cells). 3mA to a led with 3V forward drop is 9 mW which should be about 1 lm with efficient modern leds.

I picked 1lm since that was the intended brightness of the original CMG Infinity, one of the early flashaholic lights, that gave way to the Arc AAA which overdrove its led to produce around 3 lumens, seemingly amazingly bright at the time. The best known 1AAA light before that was the Mag Solitaire at about 2 lumens, so this is a perfectly usable “fully functioning” rather than “vampire” light level.

My actual idea is to make a super light and compact headlamp, along the lines of a Photon keychain light with a headstrap, and that motivates the question. I was looking at the Black Diamond Flare which is unregulated, so it is quite bright at first but depletes its batteries fast. I’m thinking to use 1xCR2032 or 1xCR2450 and a regulated boost converter, to maximize the “functional” (above 1lm) runtime. Vampirism would also be a nice feature for this sort of light, but it’s separate. If the light has a microprocessor it seems reasonable to also monitor the cell voltage and adjust power output downward once the battery gets near dead. It would still be above 2 volts for that.

My original idea had been to use a 1.5v hearing aid battery but I decided that is just too crazy. 1AAA is still possible. I don’t know why there have been so few 1AAA headlamps.

Btw the E3A from Aliexpress arrived in less than a week with free shipping.