Its the crank- takes a ton of juice. It may also be what you are saying.
I just know when I am doing a serious detail where I move the car few times- fully charged good battery SLA will read low battery warning on dash.

Your AGM is the best, what people dont realize is that AGM charges faster- yeah you are more completely charging the battery that others with SLA for same amount of driving time. You also regenerate on the downshifts with manual.
In fact a car is not meant to recharge a battery, its meant to maintain it, which is easier to do with the AGM absorption curve. I make LipePo4 packs, insane charging rate, 85% in 10minutes.

 

Thanks for responding. You have confirmed the source of the problem: there is nothing wrong with the car other than lack of use! A CTEK maintainer or similar should be permanently installed, meaning that the wire is connected to the charging points in the trunk and the CTEK "comfort extension"attached to this wire; the actual CTEK unit remains outside the car, its wire in turn attached to the comfort extension. It has taken about three times as long to write this sentence as to make the connection! It is a matter of seconds to connect the maintainer when you park the car. Connection instructions (which are very simple) are described in several threads. These maintainers can be left connected indefinitely. Each time they are connected they go through a multi-step process of battery analysis, desulphation and different charging cycles. Some models have programs for both conventional "flooded" batteries and the AGM batteries used in our cars. Use of these devices greatly extends the life of the battery and guarantees and end to problems caused by low battery voltage.
i have used these on all my cars for decades.