Macbook Air shuts down suddenly and battery drains completely.

Could be a number of reasons.

Have you tried running Apple Diagnostics to see if there are any underlying hardware issues with your MacBook Air (MBA)? Ref: Use Apple Diagnostics to test your Mac - Apple Support

In addition, I suggest that you run an EtreCheck report, and optionally, post it here if you need assistance with interpreting its results. EtreCheck is a diagnostics tool, developed by a valued forum member, that greatly aides in troubleshooting difficult Mac issues. Ref: Using EtreCheck to Troubleshoot Potential… - Apple Community

@Ruskes

That's a good start, but will result in a potentially large output. May I suggest something like the following:

• log show --predicate eventMessage CONTAINS[c] "previous shutdown cause" --style json --info --signpost --last 24h

Also, the following article would be helpful to interpret the shutdown cause codes:

• https://georgegarside.com/blog/macos/shutdown-causes/

Run this in Terminal and examine the results

log show --style syslog | fgrep "shutdown"

@Tesserax

Tesserax

There is a problem in terminal

log show --predicate eventMessage CONTAINS[c] "previous shutdown cause" --style json --info --signpost --last 24h

zsh: no matches found: CONTAINS[c]

Thanks. Teaches me to offer advice when I haven't had enough coffee. I was using Consolation 3 (from The Eclectic Light Company) to compose the search string which was successful. However, it doesn't work well directly in the Terminal. Doh! For not checking beforehand. Sorry, about that. When I get a chance I will try to provide what should work directly in the Terminal.

Sorry, but of all of the possible Previous Shutdown codes available, "8" is unknown. I couldn't find any documentation on this specific code.

All I can find is some folks have reported this code after their Mac experienced a liquid spill.

Thank you for clarifying

Here you go, this one should work:

• log show --predicate 'eventMessage contains "Previous shutdown cause"' --last 24h