This work presents experimental analysis on the local heat flux distribution for a prismatic lithium-ion battery at various charge/discharge rates. Experimental setup for a large prismatic lithium-ion battery thermal testing is developed, and experimental investigations of the thermal dissipation of lithium-ion battery are conducted under various charge/discharge rates to provide more information on battery heat generation. The aim of the present study is to evaluate the heat generated by the electrochemical reaction inside a lithium-ion cell during numerous charging/discharging cycles until reaching steady state. In this paper, the distribution of temperature is presented for a prismatic Li-ion battery at different operating conditions. The results show that a higher battery temperature is obtained at the beginning of the charge cycle and the lower temperature is reached at the end of charge cycle and the beginning of discharge cycle. Furthermore, it is observed that the increase in charge/discharge current rate increases the battery temperature, the generated heat flux and the part of the irreversible heat compared to the reversible heat. It can be observed that at C-rate of 3C irreversible heat reaches 80% of the total generated heat.