Power Output MPPT 150/60 only Batterie charging

Hello,
i can see, when batteries are nearly full charged (beginning with absorbtion) , a fluctuating power output between 4W and 50W, changing like a sinus curve. Is it from the Charge Controller MPPT 150/60 or what is the reason for this ?

Here is a link to my grafane graphs - green voltage, yellow panel power.
Booth values are from the charge controller.