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Comment by MisterTea | Hacker News Reader

I see no charge rate numbers so there is no way to compare. however, these sodium batteries are cheaper, do not require lithium, and are operable at lower temperatures of -20C/-4F. Sounds like a bit of a win and opens the door for battery options in cars.

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And the fire safety risks are significantly reduced (thermal runaway is much harder). They can also be transported and stored completely discharged, something not done with lithium ion batteries because of it degrades them much more than regular usage.

The sodium-ion batteries are said to work satisfactorily down to -40 Celsius = -40 Fahrenheit.

-20 Celsius just happens to be a temperature for which a retention ratio was specified in the parent article, and not the limit of the operation range.

Operating at -40 is one thing, charging at -40 is another.

i would have imagined that charging at -40 is easier than operating at -40.

I have no idea how true this is, but the press releases claimed that both most of the capacity is retained down to -40 and that the charging speed is proportionally retain down to -40, and that this is the meaning of the operational range.

Right, good to know.

When you're at a charger you can easily spare the 3-4% of battery capacity it takes to heat the pack by 40C. Less if you use a heat pump.

How many people let their ICE engine block get that cold?

For -40, the anecdote for combustion engines used to be that in Siberia you turn on the car's engine in november and off in march.

For -20 though, it can happen each year in 4 season temperate climates and north of that.

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