Li-ion battery costs.

[grarpamp]

> https://techxplore.com/news/2021-03-reveals-plunge-lithium-ion-battery.html
> I've been following magnesium-ion batteries for a few years.

https://en.wikipedia.org/wiki/List_of_battery_types
https://en.wikipedia.org/wiki/Comparison_of_commercial_battery_types

Some people are using nickel-iron NiFe for home...
cheap, easy to maintain, simple chemicals,
last forever, simple charging, take lots of abuse.

Others pull ions from junked car packs.
Or just plain lead-acid.