Battery full charge capacity suddenly decreased. Is there a way to manually force a capacity check to restore battery capacity?

Hi Troublesome. I'm Greg, an Independent Advisor here to help until this is resolved.

1. Compare the install you did with this gold standard Clean Install of Windows which will stay that way as long as you stick with the tools and methods given, has zero reported problems, and is better than any amount of money could buy: http://answers.microsoft.com/en-us/windows/wiki... Note the driver steps are so important they are printed in red. You must also delete all partitions off the drive (with all other drives unplugged) or it is NOT clean.

The reason I ask you to do this is because no one of millions who have followed the install in that link has ever come back to report problems that I have seen. It is also a great learning experience that will make you permanently the master of your PC because you will learn what works best and have applied it with your own hands.

2. Right click Start to open Device Manager, under Battery choose the battery device, then Driver tab, then if available Roll Back the driver. If not available, choose Uninstall Driver, restart PC to reinstall.

See these fixes for Battery Not Charging:

https://www.groovypost.com/howto/troubleshoot-b...

https://www.kapilarya.com/fix-battery-plugged-i...

Check the manufacturer's Support web page for your full model number to see if there is a battery issue or recall for it. Remember you have a full one year warranty for PC and parts replacement or repair so I'd use it if still available.

Run the battery re-calibration here: https://www.howtogeek.com/172271/how-to-calibra...

Then generate a battery report and post it back here: https://www.groovypost.com/howto/generate-batte...

If this was caused by Windows Updates then you can check which were installed at Settings>Update & Security>Windows Update under Installed Updates, then uninstall them from the link there, and hide with the Hide Updates tool downloaded from here: http://download.microsoft.com/download/f/2/2/f2...

You can also use System Restore to get before the problem began, then check for Updates with the Hide Update tool and hide them: http://home.bt.com/tech-gadgets/computing/how-t...

If this was caused by a Version Update then for 10 days you can roll it back in Settings>Update & Security>Recovery and then hide it until it matures using the Hide Updates Tool which is explained more here:

https://www.howtogeek.com/223864/how-to-uninsta....

If nothing else helps then you might need to replace the battery. However I will tell you that most OEM after-market batteries and chargers have problems so I would only buy the official manufacturer's battery from the PC maker to be sure.

I hope this helps. Feel free to ask back any questions and keep me posted. If you'll wait to rate whether my post helped you, I will keep working with you until it's resolved.

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Have you calibrated the battery since the reinstall?

https://www.howtogeek.com/172271/how-to-calibra...

Also if it's within a year of purchase the manufacturer's Support needs to help you correct this or replace the battery.

I decided to follow another step, where I charge up the battery overnight and then let it drain in the calibration process. This morning, I generated another battery report:

It has been plugged in and charging since about 2+am. For the next hour or so, the percentage for some reason did not increase at all, and then actually decreased! By the way, this laptop is a little over 4 years old, so its no longer under warranty. However, by my cycle count of 399, it should not be in such a dire state 

Another thing is, since I made the first battery report, these figures, particularly cycle count has not changed at all, which leads me to suspect there might also be an error here.. Is there any way to get a more accurate report? Either way, I have unplugged the laptop now, and will follow the calibration steps and update when that is done. Thank you for your help so far!

Did you contact the manufacturer? They are the only ones who can do something about your battery. It is covered by warranty and may even be under recall or have another known issue. A battery is hardware, from Asus, not software like WIndows.

Thank you for your detailed response, and the excellent write up on your fresh installation thread. So far, I have completed the fresh install, the one big difference between that and my previous reformats is that this time there was the additional step of clearing the partitions. At this moment, I have also already updated the drivers from the official Asus website and all recommended windows updates. The battery report remains the same however. A strange thing is that I have been plugged in with charging on from before the reformat, but now the battery percentage is lower 90+ to 85% currently. secondly, the battery light, orange for charging and green for full, is showing green, even though the battery percentage on the screen says 85%! I will continue to follow the second step, and keep you posted on the results. Thank you for your help so far! Technical issues always get really frustrating for me so I really appreciate your help.