because I have an "excess" of PV panels.

Which aligns with as much as one can afford. If one calculated an exact amount they would not be able to get the results you are getting.

> "excess" of PV panels ... aligns with as much as one can afford.

does it? Panels are not the most expensive part of the system any more. Overcapacity of panels isn't the bottleneck any more. Battery capacity or roof space might be instead.