Inconsistent battery life

[Fozman1]

Hello,

Purchased my HP Spectre x360 Laptop - 15-eb0001na on 16th March 2021. Upgraded Windows 10 Home to Pro, installed Office & other usual programs. Main usage is with MS Office, occasional video meetings over Teams or Zoom & usual surfing - so no really heavy processing.

This laptop was an upgrade to my previous one: an HP Envy x360-15.

However, with the Spectre, the battery life is at best mediocre, at worst abysmal & certainly well away from the "long battery life" indicated in the specifications at https://store.hp.com/UKStore/Merch/Product.aspx?id=2T980EA&opt=ABU&sel=NTB of "up to 6hrs 45mins"
Most video settings are HP defaults, th eonly change is to screen brightness which is at 81% (I'd prefer this to be brighter, but realise that this will impact further on battery life).
Having tracked timings, battery life seems to average at around 3 hours - slightly longer if a period left on, but not used (for example if I'm away from desk). However, on many occasions, I've shut down laptop at night charged to 100% & on switching on the following morning, battery shows around 50%-60% charge left. At the moment "Fast Startup" in Windows is NOT enabled, so it can't be that eating battery power.
Any thoughts, or suggestions would be welcome as, with the exception of battery life, the laptop is brilliant!

[Fozman1]

Further update... left laptop on charge overnight.

Unplugged this morning as "white light" indicating full charge illuminated. Have just switched laptop on & battery is already down to 89% without laptop even being switched on.