Sadly, similar issue to everyone else. Right after a Big Sur installation, battery is now totally dead at 1% (now tell me to service it) and it tells me that it isn't charging. Some facts about my situation : MacBook Pro 13 2016 (2 thunderbolt port, base config) Was successfully updated to Big Sur (Clean install) at OS launch (November). No problem. Was also updated to 11.1 at time of release. No issue. I did a clean install, followed the instructions on Apple Support to prepare the computer to be sold. I used my Install Media from november, so it was 11.0 and not 11.1. Battery was healthy before, 242 cycles (changed two years ago in the recall for this particular model). Battery was at 100% before installation. Then 1% (actually, "0" according to Coconut Battery) on first Big Sur boot. In System Report, battery condition was "normal" but at 0 mAh charge, and not charging. Did another clean install, this time latest version of Catalina. Same issue, except now it actually tell me that the battery need service (did not tell me that in Big Sur.) Tried SMC and PRAM. Computer won't turn on, even when plugged in, with the power button. However, if I unplug the charging cable for some seconds and replug it, eventually it automatically boot. So basically, I highly doubt that Big Sur simply "detected" that my battery was faulty. There is a clear pattern in this thread.

New information : (See my previous post from some hours ago) Had the same issue : battery won't charge, 1%, status : get battery serviced. When I unplug MBP instantly shut down. Tried SMC and NVRAM. Didn't work. Well, turns out now ... it seems I have solved it ! (for me at least) Basically from what I understand, firmware updates are linked to macOS installers (don't quote me on this, but that's how I understood it) So my plan : Clean install from the earliest macOS version supported (in my case : Sierra), then upgrade (not clean install) one version after another until I reach Big Sur, using downloads from the App Store (Use this link : https://support.apple.com/en-us/HT211683) What happened. Sierra Clean Install (from bootable disk created with CreateInstallMedia command from Terminal) : In the installer, lots of shenanigans in Disk utility and terminal to revert from the multiple volume APFS drive to HFS+ one (Sierra was the last non-APFS mac OS). Eventually I had what really seemed like a simple HFS+ Macintosh HD on my internal SSD. Then installed Sierra. Partial success, same exact symptoms : Battery won't charge, Instantly shutdown when unplugged from charge. Difference : 100% charge shown instead of 1%. However still unable to charge battery and still showed as "needing service". 2. Update to High Sierra (using this : https://support.apple.com/en-us/HT211683). SUCCESS ! Battery condition normal, 100% charge, can run on battery without problem, can reboot on battery, no issue. Like nothing happened. Somehow in the High Sierra Upgrade it did something to the firmware. Now the MacBook Pro is able to use battery as it is supposed to. Right now I'm moving further, one version after another to get to Big Sur. - IMPORTANT NOTES : This is what worked for me, but I took many risk playing with drives in Disk Utility. DO NOT TAKE THIS AS A TUTORIAL. But, I think the basic strategy of going back the version of macOS that shipped with your Mac and moving forward one OS update after another is a good and safe strategy. It worked for me apparently. Also, one very important thing about this : THIS WAS A SOFTWARE ISSUE. My battery didn't need replacement, it wasn't hardware. Even if my method don't solve your issue, at least it's a sign that Apple should be aware of this problem and work on a way to solve it via software.