The abundantly available precursors, the environmental friendliness and the inherent safety are always a driver for new energy storage applications and also much interest in Na-ion batteries is generated because of the lower material cost compared to Li-ion batteries. In the recent decade, the crucial need for the improvement of battery safety is emphasized and safety remains a critical barrier for this technology. Despite safer battery materials, battery thermal management could be a key to safer post Lithium technology. Na0.53MnO2 and Na3V2(PO4)3@C based materials as cathode and coconut shell-derived hard carbon (HC) as anode were studied in this work. Full cells were developed accordingly by balancing the cathode/anode capacity ratio including the irreversible capacity loss in the first cycle. The safety related parameters including the heat generation during charging-discharging and thermal abuse tests have been executed by the means of sophisticated calorimetry instruments. The total heat generations were investigated by 3D-Calvet MS80 calorimeter (Setaram, France) under isothermal conditions at 25 °C. The constant current, constant voltage (CCCV -I < C/20 or t > 60min) test profile were employed both in charging and discharging with rate of 0.2 C. In full cells heat generation was measured and it was observed that in the charging process less heat was generated than in the discharging process. Of course, the irreversible heat generation is higher in case of discharge, which corresponds to a higher internal resistance of the cells. Finally, the exothermal reactions were identified by a Heat-Wait-Seek test in an accelerating rate calorimeter (THT, UK) as thermal reactions identification is important for the optimization and design of a battery pack. A stack of 2 coin cells was placed in the calorimeter chamber to get sufficient thermal signal. Using this procedure different exothermal reactions could be identified. Thermal data and exothermal reactions give a relationship between different critical thermal and safety related issues in beyond Li batteries. The determined thermal data, out-gassing analysis and safety parameters on coin cell level are necessary for the design of a safe battery, which is a prerequisite for upscaling and for market acceptance for the new technology.