flashlight

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.