In the apogee of electronics, electrochemical batteries gain importance, not only in electrical vehicles but also in consumer electronic applications. Alongside with lithium (Li-ion) batteries, nickel/metal hydride batteries (Ni-MH) are the most widely used. While there are mathematical models available in literature, little is known of its aging. This work presents an electro-thermal model of a generic nickel/metal hydride battery using CFD technics in Matlab® achieving suitable accordance with early researches. Aging is then assessed by means of irreversible entropy and by changing key parameters such as porosity and concentration of cyclable species. Charge and discharge cycles are conducted, concluding that the electrode’s loss of capacity is the largest contribution to the battery’s aging.