TURIN Thanks for your wealth of knowledge and your no nonsense style.
It seems that there are some minimal demands on these Batteries when the a/c is powered down, eg, POS lights, FUEL indicator, DOOR position, etc.
A question I asked long long ago. These Lithium Ion batteries have a well proven long life as to SOC, and a less proven profile relative to daily use, discharge, environmental factors, and Handling error.
Would it have been perhaps a better idea to have a powered down 'Battery system' of a more proven nature to accomplish the mundane chores we are discussing here?
The Backup Batteries are a flight critical system, and perform just fine in that regard, it would seem.....?
Penny wise, pound foolish?