Battery state of charge.

[John]

Take a 12v battery which from new starts at around say 12.7V.

When it reaches 11.9, it is supposedly discharged.

How can a battery at this level still turn a car over fine without any trouble?

Or is this not what is being referred to?

(Measured on a multimeter)

 

[RichardF]

For a lead acid battery in good order a fully charged cell is around 2.1v consider it discharged @ 1.75v. Measured during load (cranking) it can drop off to 10+ V.

A low battery may crank a car, but the nominal voltage may not be enough to power up the electronics.

A decent battery, no drain, fully charged will settle off around 12 + V after several weeks.

More to it than that though, google it and digest.