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I have 6 batteries for my laptop. I used powercfg /batteryreport to check "Full Charge Capacity" for each of them.

Then I wrote a quick Excel VBA script that enters total elapsed time in a cell every 30 seconds and saves the file, and counts down the seconds in another cell to the next save. After the battery runs out and the laptop powers down, I plug it in and power it back up, and check the last-saved total elapsed time. I ran that script for each of the batteries after charging them up to full charage.

That may not be a realistic measure of real-world battery life, but I think it's useful for comparing the batteries to each other, so that I know which ones to take with me when I'm not taking all 6.

I'm seeing no correlation between powercfg /batteryreport "Full Charge Capacity" and the total elapsed time measured by my script. Any idea why that might be?

BTW all 6 batteries are genuine branded OEM.

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  • Why would you expect that behaviour? You have used an arbitraryoad/test which does its calculations in an entirely different way to the OS. Realustically, the runtime is an indirect measurement of the capacity based on history and voltage drops.
    – davidgo
    Sep 5, 2021 at 7:35
  • @davidgo I'm confused -- are you saying "Full Charge Capacity" isn't related to battery life? If so, what's the practical value of knowing "Full Charge Capacity"? Sep 5, 2021 at 15:53
  • Full Charge Capacity IS directly related to battery life. Runtime, however, is highly variable depending on power draw - a highly confounding factor. Its also possible that you have bad cells which are drawing power from the others which is another confounding factor. Another important element is that the reported capacity is coming from a chip in the battery. This is a rough estimate dependant on how the batteey was used. If you had different usage profiles for the batteries, or you gave left them sitting in a discharged state this can significantly alter the reported vs actual capacity.
    – davidgo
    Sep 5, 2021 at 19:04

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