I've generally heard that it's ok to discharge LFP batteries to 0%. You just shouldn't store them that way (or at 100%) for long periods. Keep in mind that LFP has maybe half the energy density of the highest density NMC batteries, and sodium has maybe half that of LFP. Sodium really doesn't sound that good batteries for portable devices.
It wouldn't surprise me if there's not yet any sodium charging chip for small consumer electronics like this. I haven't heard of a sodium powered flashlght, phone, or anything like that before. The only sodium consumer device I know of right now is a Bluetti power station which has 900WH: https://www.bluettipower.com/products/sodium-ion-battery-pioneer-na
It got some attention at its anouncement but tbh it's 10lb heavier and $300 more expensive than the 1024WH lithium version (Elite 100v2). So it's for early adopters only.
If you want to charge a small sodium cell, you can probably program an MCU to deliver the right charge profile, along with a few small external parts. That's how Apple phones worked at least in the past. They saved a fraction of a penny by just incorporating some extra logic and code in their big ASIC instead of having a separate charging chip. It's kind of interesting that the charger was programmed in Forth, on a special Forth processor (b16-small) that they cooked into a hardware macro: https://bernd-paysan.de/b16.html . They hired Bernd (the b16 designer) to write the code and it was pretty intricate because of the cpu's limitations. I don't think I'd have used that approach ;).
Wurkkos TS27 has an LFP battery and is beefy and advertised as a duty light, and it seems nice except then it has this silly RGB ring light that turns it into a fidget toy. I lost interest because of that. YMMV. :)
Added: I just looked over the kickstarter page for this light. The battery looks to be 10,000mAH nominal, size 32140 which is 4.7x the volume of a 21700. Voltage is 3.0 nominal but looking at the discharge curve at -20C it looks about 2.5V on average, so 25 WH. Not that much better than a 5000mAH 3.6V 21700 (18WH). The sodium is somewhat worse but still viable at -40C and I guess it might be beating lithium by then too, plus it has the ability to accept charging at -40C. I don't see super-cold charging as very important for a flashlight (if you're able to charge your light you can probably keep it at least a little bit warm), though super cold operation can be helpful.
Also, this is a 2500 lumen light which is a far cry from the old Maglights that were perfectly usable. The classic 2AA minimag was around 5 lumens over most of its runtime, the huge 6D was something like 36 lumens, and the nicad powered Magcharger was about 180 lumens. Surely for changing a fuse, a low powered headlamp is preferable to a huge handheld ;).
Sodium batteries are mostly of interest for grid storage or maybe stationary home batteries once they get cheap enough. They are sort of marginal for EV's but might find a place in some cold weather ones. Having them in a few weird flashlights isn't going to help ramp up manufacturing volume compared to that. The real demand will come from power utilities buying gigawatts at a time, not a few flashlight nerds.
I remember the Eternalight and it went through a few nicer incarnations over time The designer was a regular on Candlepower Forums. IDK if the company still exists. The product was cool in some ways. IIRC it uses 5mm leds. The first production flashlight with a Luxeon was the Arc LS and I had two of them. I think the semi-custom McLux TK may have been earlier but my memory by now is hazy. I still have mine. Sodium batteries are different. Aside from the very niche advantage in cold weather charging, they are worse in every way than lithium. The main feature that makes them interesting is potentially lower cost per KWH in the long run. That's great if you want a 100KWH off-grid battery for home, and maybe it can find its way into economy EV's. But nerdy flashlights, nah, battery costs are not much of an issue already. The bigger light and fancier charging and regulation circuitry negate any advantage. We could already use LFP batteries if we wanted to, but we almost never do.
Only living people can win the prize. If they die between the announcement and the ceremony they still get it posthumously. I'm pretty sure that has happened now and then.
"Let me tell you a secret: chess is the most violent of all sports. I’m a pretty good soccer player and a long-distance swimmer, and recently, I’ve taken up tennis, but I can tell you that there’s no sport as competitive – yes, I’ll say as rough – as chess. The only goal in chess is to prove your superiority over the other guy, and the most important superiority, the most total one, is the superiority of the mind. And there’s no luck involved, no picture card coming up at the right time, no roll of the dice that saves you. It all has to come out of your head. You whip him or he whips you. It’s as simple as that. Or as complicated as that."
--Garry Kasparov, former world chess champion
So make a lichess.org account and wreak some havoc over the chessboard :).
I haven't had trouble with the E3A O-ring but for such a minimal setup I'd consider a coin or button cell light, or maybe a 10180 light. Those can be much smaller than an E3A.
I guess see what the E3A page says about the finish these days.
I like the E3A a lot. It's the smallest 1AAA light that I know of, and the led tint and beam are nice. Unfortunately, mine went poof a while back: https://lemmy.ml/post/22807017
I have not gotten around to making more serious efforts to examine it and haven't replaced it yet either, but someday. The KC1, meh, it doesn't excite me that much due to its larger size. The 10440 battery format isn't so appealing either, imho.
I've sometimes thought of getting one of the tiny 10180 lights with a built-in USB charge port. I do also have a few other 1AAA lights kicking around so maybe I'll dig one out and start using it. The format seems less important now than it once was though.
Added: note that for whatever reason, the E3A in slate blue has a harder anodized finish than the other colors. So I got that one. You might consider doing the same. It was about $1 more, no big deal.
I noticed another review of this light at https://tgreviews.com/2022/07/23/sofirn-d25lr/ that has some useful extra info including a partial teardown photo, and a measurement of the parasitic current at under 1 microamp, very good. I think that review is of an older version of the light, since it has micro USB while mine has USB-C.
My brother had a micro-USB light (now lost) of this series, and it seems to me that the build quality of that light, while not terrible, was worse than the two I have now (H25LR and H25L. So maybe they got better at the time of the switchover. I still highly recommend these lights and don't really want any more 18650 headlamps unless someone makes a suitable Anduril one.