Fwiw Molicel INR 21700’s are rated for discharge down to -40C (pdf) though charging only down to 0C. I don’t see a need for a sodium ion flashlight just yet, but I’m posting anyway since I guess it’s news despite being stupid.
Fwiw Molicel INR 21700’s are rated for discharge down to -40C (pdf) though charging only down to 0C. I don’t see a need for a sodium ion flashlight just yet, but I’m posting anyway since I guess it’s news despite being stupid.
I would like to know what charging chip they are using for charging it, because there aren’t any mass produced sodium ion charging chips that I have been able to find for my own projects and it 100% is an off the shelf part.
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 ;).
I know of one chip that is a sodium ion charger but I think it is only available in China and not in the west since the tech is picking up more speed there.
I guess you technically can use a Lithium ion charging chip with a programmable charge voltage like the BQ25300 but the problem is that almost every chip with a programmable charging voltage also has an under voltage shutoff to prevent deep Li-Ion discharge (usually 3, 2.5, or 2V), but that also means that you can only use like 50-80% of the already limited capacity.
One of my next projects is using GreenPak programmable signal matrix (like a very mini FPGA) to make a sodium charging chip I can put in projects.