How do I optimize Apple Watch battery charging to 80%?

I have had my Series 10 watch for around 6 months. It has always had a regular charging routine, about 30 minutes in charge at around 6:30 in the morning.

Until about a week ago it always displayed the incomplete charging circle, charging to around 80%. That was more than enough for a days use for me, and usually had about 40% left by the next charge.

then one morning it decided to charge to 100% and has carried in doing that. Battery health is showing as 99%.

I don’t need it to charge to 100%. Is there anyway to force it back to the 80% as there is on my iPhone?

[Re-Titled by Moderator]