Gaussian System in the sense that all the variables involve to define the system should be Gaussian distribution? I read so many papers  using Kalman Filter for Battery modeling, SOC estimations. 

Discharged voltage / terminal voltage is one observation of a battery. So I discharged a battery and the profile of the battery discharge is attached in the figure. The same discharged terminal voltage is plotted using the Histogram which is also attached in the same picture. 

The Histogram plot doesn't reflects as perfectly to be Gaussian. So how do i explain this data of voltage discharge? Can i assume it to be Gaussian ?

Kindly refer to the attached picture. 

Appreciate your time !! Thank you very much !!