I used Win X to shutdown and compared the rate of battery discharge to using a Command Line shutdown (shutdown /s /f /t 0) and guess what? They're hugely different.
Win X (GUI) shutdown -9.2% drop after 21 hours.
Command Line shutdown -0.5% drop after 19.5 hours.
So far, from what I've found to date, the only method to protect a laptop battery from excessive exercise and likely a pre-mature failure is to use a Command Line shutdown or use the first release version of 2004 or an earlier OS.
This confirms (at least on this MSI laptop winver 2004) that both S3 Sleep and any GUI triggered shutdown has changed. :-(
I ran some tests of battery discharge after shutdown.
- In each test,1 I waited until the battery was shown as 100% in the SysTray, then
2 I shut it down & pulled out the power cable, then
3 waited for the test period, then
4 turned the computer back on, then
5 read the battery SysTray reading as soon as the computer reached its Desktop [using netplwiz automatic login].
- I had intended to run the full set of:1 Shutdown through Start button, Power, Shutdown
2 Shutdown through command line - shutdown.exe /s /t 0 /f
- I had intended to think through uncertainties in the results quite carefully: Recording the time, Reading the current charge state. I had also intended to consider the current battery state [Last full charge / Design capacity] so that results now could be compared to results next year.
The test computer was a Dell Inspiron 1545 [from 2010, so it does not even know how to spell S0] on Windows 10 Home x64 Version 21H1 Build 19043.1110. Its battery manages about 80% of its Design capacity so battery deterioration should not affect the results.
Test 1.1 - 6 hours, battery went from 100% to 95%
Test 1.2 - 8 hours, battery went from 100% to 94%
At this stage I already wondered if lack of the accuracy in the SysTray indicator might mean that these two results were essentially the same and that both represented nothing more than the power used up by starting the computer.
Test 1.3 - 21 hours, battery went from 100% to 98%
I concluded that, since there is definitely power used up during the start-up, if there is any power drain during shutdown its value is so small as to be swamped by the start-up power usage [that might itself be variable] & obscured by inaccuracy in the SysTray indicator.
It didn't seem worthwhile doing the command line tests.
Our experiences in this respect are significantly different. I don't know what the reason might be.
All the best,
Denis