Why does my Intel MacBook Pro battery drain when off?

By far the easiest way to cause poor performance, instability, overheating and crashing is to install ANY third-party speeder-uppers, Cleaners, Optimizers, or Virus scanners, Bit Torrent, or a VPN that you installed yourself. They are relentless in scanning your files, non-stop, looking for virus-like patterns in Everything, or looking for files that have changed. When completed, they do it all again.

The idea that a third party, with no special knowledge of the inner workings of MacOS, can somehow find a simple way to protect or speed up your computer — that is not already being done by MacOS itself — suggests that the MacOS developers are somehow "holding out on you". That is absurd.

You should remove any and all (other than Apple built-in) virus scanners, speeder uppers, optimizers, cleaners, App deleters or VPN packages you installed yourself, or anything of that ilk.

Your exceptionally well-crafted Macintosh computer does not accumulate filth that needs any third-party anything to clean it. Everything needed to run it efficiently was included in the box, except ONE: a drive on which to store a second copy of your files in case the first copy is damaged or deleted by accident. The backup software, Time Machine, is already present -- integrated deeply into MacOS.

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Next up is Non-native File Sync-ers.  Dropbox, Microsoft OneDrive, Google drive and others are in this category. Since they were ported from that other OS environment, they IGNORE the Mac File System Event Store (that could tell them EXACTLY what folders have changed recently) and instead do a a Brute-force read of all your files, and all the files stored on their drive on the Internet. This punishes the ability to get any data (including speed test data) through their enormous and frivolous file reading and re-reading.

They are also 'on the phone' checking and re-checking the synced file stored on the internet. Between constant scanning and constant Internet access, this uses a LOT of resources -- far more than Apple-native File-Syncers like iCloud. Running File-Syncers when not actually needed still consumes a lot of computer resources. You should NOT be launching these at Startup, but instead launch only when needed, and quit when Sync-ing is complete.

Backup-to-the-Web Utilities are also in this category. Your backup should be on a local drive, not on the web. If you question this, just ask.

Last up is Apple Sync-ers, such as sync-ing your iPhotos Library to iCloud. A substantial iPhotos library can take many, many hours to bring up-to-date. Doing that update can produce an Internet logjam until it gets completely up-to-date.

Ran a virus scan.

Pointless on Macs, and likely to be detrimental.

If I leave the battery fully discharged for an extended period of time I might as well use the MacBook as a wheel chock for all the good it will be to anyone.

You might as well, because storing a lithium polymer battery in a fully discharged state for an extended period of time is certain to kill it.

It seems as though that Mac's battery is simply no good. A Mac that has been shut down will consume almost no battery power, and a properly functioning battery should hold a charge for months in that condition. Have Apple evaluate it: Official Apple Support.

Uninstall the "virus scan" garbage before you do that. Rule 1 of Macs is don't install junk.

NB >>

All of the below applies to those with ORDINARY risks. If you are a high profile activist who could be the target of nation-state type attacks, you will need to take FAR more precautions than ordinary users.

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MacOS shares a lot of the lock-down mechanisms developed for the iPhone. Applications are all sand-boxed with a list of the resources they require, and they cannot ask for anything outside their sandbox without crashing. Signed Applications are checked that they are from legitimate Developers, and Notarized Applications are delivered with the assurance that they have NOT been modified since their release by the Developer.

From MacOS 11 Big Sur onward, the system is on a Separate, crypto-locked System Volume, which is not writeable using ordinary means. Any unauthorized changes to the crypto-locked volume are quickly detected and you are alerted.

So you could store just about every malware known to mankind on your Mac, and your Mac would not get infected spontaneously. Scanning for virus-like patterns might make you feel a little better now, but non-stop scanning is outdated nonsense, and a tremendous waste of resources.

Nothing can become Executable Unless/Until you supply your Admin password to "make it so".

About the read-only system volume in macOS Catalina or later - Apple Support

About the read-only system volume in macOS Catalina or later - Apple Support

What is a signed system volume? - Apple Support

What is a signed system volume? - Apple Support

Signed system volume security in iOS, iPadOS, and macOS - Apple Support

Signed system volume security - Apple Support

Effective defenses against malware and ot… - Apple Community

I think you have determined experimentally that you can NOT store that computer with that battery without making power available. Be sure to also enable battery health management, for longest possible lifetime.

Batteries are a wear item, like soles of your shoes or tires and brake-pads on your car. Sooner or later, we expect to have to replace the battery.

It sounds like your five-year old battery may not be equivalent of new any longer.

Hello. I have the same Macbook Pro 2020 intel 1TB 16GB Ram..... and the exact the same issue.

Do you found a solution?

TKS