It looks like I have managed to defeat this and my battery now fully recharges to 100% booted in Windows. It does not appear to be a hard firmware update, although it does persist even when powered off or booting into another OS such as Linux that does not run the Fujitsu software.
To check whether removing the software would work, I shutdown and powered off the laptop, then booted into live MX Linux from a bootable USB stick. The charge level was still stuck at 65%. I then ran it on battery until it dropped to 60%, but it didn’t seem to charge when plugged in. So I got a power plug meter (Kill-a-watt equivalent) and it showed as only drawing 18W, i.e. too low to be charging. I then ran it on battery in 5% stages and it wasn’t until it fell below 50% that it would start charging again, i.e. power meter showed 68W. Once it reached 65% Linux displayed a pop-up to say the battery has stopped charging and indeed the power meter fell back to 18W.
This was the battery status at the time and it was plugged in despite showing ‘discharging’:
Anyway, I tried the trick earlier that let me temporarily charge to 100% (see below) and when I booted back into Linux, I saw the battery status was at 72% and charging. However, when I booted back into Windows, the charging stopped the moment that Fujitsu Battery Charging Control Utility popped up. So this gave me an idea - Let’s try disabling it instead of uninstalling it. Sure enough, once I used the trick to get the battery charging again, it continued charging even when booted into Windows.
Here’s the steps for anyone affected (who’s battery is not recalled) and would like to charge their battery back to 100% again:
Download the Autoruns utility and extract it in a new folder.
- In this folder, right click ‘Autoruns’ and choose ‘Run as Administrator’, then click ‘Yes’.
- In the ‘Filter:’ box at the top, type in: fujitsu
- Clear the check boxes for the following 6 items:
- Close out of Autoruns, then shutdown the laptop.
- Unplug the power cord and remove the battery.
- After 30 seconds, install the battery again. This clears the “firmware” out of memory.
- Connect the power cord and boot into Windows. Check that it is recharging:
Finally, to double-check that it was charging past 65%, I booted back into Linux to check the voltage. When it stopped at 65%, the battery voltage was around 12V, i.e. 4.0V per cell. A fully charged Lithium Ion cell is typically 4.2V/cell.
12.506V / 3 = ~4.17V / cell, which would be about right for the 97% level it mentions.