Hi Zoran, Im not overly experienced in 12V but know just enough to get myself into trouble 😅.
From my experience any power loss or poor performance comes down to many possibilities - bad cells, poor grounding, poor contacts, a short in connected equipment, incorrect charging, sulfation to name a few.
Re reading the post (properly this time) & Fab's comment I would say its accurate with the amount draw in the figures.
@frankS It is very important imo to have a good battery monitor to know what SOC you are at as billmack suggests with an AGM you only have 50% of useable power before you start to reduce you batteries lifespan if constantly drawn below that. How many volts is an AGM at 50% SOC? Well thats debatable, I have seen figures as low as 11.95V to 12.51V. I am going with my AGM's battery manufacturer that states 12.05V is 50% SOC.
https://www.victronenergy.com/battery-monitors/bmv-700h#pd-nav-image
The other thing I have learnt about AGM's or anything 12V for that matter is that whats on the label & what any manufacturer can state in their specs on AH capacity & charge/discharge rates etc is subjective & they usually over inflate the figures.
Eg. One branded 140Ah AMG can weigh 35kg while another branded 140Ah AGM can weigh 45kg. How can the 35kg battery be a true 140Ah??
Its a similar thing for solar panel/blankets to.