MBP 2020 Battery drain when switched off

Good day everyone,

I have a Macbook Pro 13" 2020 with 4TB ports.

To start off, when in use on battery, the battery lasts a long time and is of no issue so I think the battery is very ok. Coconut Battery provides the following metrics

• Load Cycles: 66
• Age: 663 days
• Full Charge Capacity : 4655mAh (94.8%)
• Design Capacity: 5088mAh (91.5%)

The attached screenshot from Coconut Battery shows, what I think, is a good, healthy battery.

However when I Shutdown (not sleep) the laptop the battery keeps draining at an inexplicable fast rate.

Most of the time I use this unit on power so the battery gets charged. Then I shutdown and leave it for a week. When I power up next the battery is at 85% - ie: it consumed 15% while shutdown!!!

I am running Monterey 12.6.3 and do not wish to move to Ventura at this time.

What could this be I how do I manage it?

Thank you for you help.